Got a Real-World Weapon, Armor or Tactics Question? Mk. XXV

[Mr Beer]

I find it quite surprising that a mere 13 g kinetic bombardment projectile could pack such power. I guess their aerodinamic shape helped quite a lot to reduce air resistance and achive high terminal velocity...

Yeah, if I'd have had to guess, I would have thought they'd need to weigh more like 100g to 200g.

I find it very surprising too. I wonder if they would be able to make such efficient darts in a medieval tech setting. Flying at 1000m altitude and dropping 50 of those each whilst travelling over a moving convoy could certainly cause some casualties even with the low accuracy. At least a great harassment method.

My guess is that medieval tech would be up to the challenge. The complexity is trivial. The metallurgy required is presumably below what was used in swords or armour. The improved darts were developed well before computer modelling, really all they needed were various designs and bombing runs to test penetration.

[Carl]

So I have had a good think about possible biology for plausible (non-magical) bird humans. I am not going to go into much detail of how they evolve, because the proposed model of being like a stereotypical angel, with separate arms and wings, would be extremely implausible to evolve when all other vertebrates operate the same 4 limbs principle. A true flying humanoid is more likely to be like a bat, and not having access to the arms for operating weapons would drastically reduce their combat potential, with dive bombing and blind bombing using simple drops from handheld munitions being the only practical aerial attack methods ( I doubt they would be able to use belts/pouches whilst flying). In a bat-like scenario, they would be limited to the (still very useful) intelligence and communication roles.

First of all- size and weight.

The heaviest flying (and arguably largest) known bird ever is this beast, Argentavis magnificens. It is estimated to have weighed about 70kg, a height of 1-2m and have a wingspan of 5-6m. This conveniently puts it at about the size and weight of a skinny human with wings instead of arms. So as a very quick proof-of-concept, flying humans could work on a biological level.

We can expect a humanoid that is capable of reasonable function on the ground (so walking and using arms as a normal human can) will have a much greater weight burden than a bird, which is focussed on flying. Therefore our flying humans have several options:
An even greater wingspan than above (this has increasingly diminishing returns)
Some reduced function over normal humans, the easiest would be very underdeveloped legs which would result in much poorer walking ability
Reduced size of the human attached to the wings, to bring the weight down.

The info we have been given about these birdpeople is that they are similar in size to normal humans, and have similar capabilities to humans, but with the addition of flying. I think it is reasonable to expect a degree of reduced function in walking and running endurance, due to lack of use compared to a conditioned human, and that could drop the weight by 10kg or so at most.

Lets assume a slim human of roughly average height, about 50kg (7st. 12Ib) and 1.6m (5' 3"). This is without wings. The size of wings that would be needed to support this is pretty big. Birds apparently have a wing-loading between 1-20kg/m2, and the theoretical upper limit to maintain avian flight is 25kg/m2. The Argentavis bird above had a wing loading of 8.6kg/m2. At a wing loading of 20kg/m2, the wing area would have to be 2.3m2 just to support the body, not including the wings themselves. However, this seems to be for ungainly birds like waterfowl and waders, which don't need good aerodynamics. Our flying humans probably have to be fairly manoeuvrable, so lets use the wing loading for Argentavis, as it was a bird of prey and may have hunted.

Working out the weight of the wings themselves has been challenging. However, I found this source, which states that the wings of a bald eagle weigh about 0.9kg for a 2.3m wingspan, and I've discovered that the similarly sized and closely related white-tailed eagle has a wing area of about 0.9m2. This means about 1kg per m2 of wing. From this, we can work out a very rough estimate of how much wing is needed to carry our birdperson with a wing loading of 8.6kg/m2. This gives 5.8m2 for our human weight, and a wing area of about 6.6m2 when including the weight of the wings. Using the size of Argentavis' wingspan compared to wing area, we can work out a wingspan of roughly 7.6m.

This gives the total size of our bird people as about 55kg, with a wingspan of 7.6m. This is not hugely bigger than Argentavis, so we can assume our bird people are reasonably manouevrable, but would have great difficulty in taking off. This is their most vulnerable time. They also would be far less agile than falcons and eagles and hawks, and would only be able to sustain rapid flight for brief periods (flapping the huge wings). This is likely also an underestimate- I've not taken into account the differences in musculature across the shoulders and chest needed to operate the wings, and this would likely add a good few kilos more, and correspondingly more wing space (apparently, flapping muscles require ~17% of a bird's bodyweight). In addition, the wings themselves may need to be a bit heavier near to the torso to support their own weights, so my wing weight estimates are likely too low. I may come back and redo my calculations to take into account a beefy chest for wing flapping.


Speed needed to maintain flight.

Argentavis apparently needs at least a speed of 11m/s (24.6mph, 39.6kph) to sustain flight. I would suspect a similar speed would be needed for our flying human, as we have given it the same wing loading. The cruising speed for large birds is around this speed too, so basically our bird people would likely stay at about 25-30mph the majority of the time. Interestingly, the maximum gliding speed increases with the size of the bird, so the bird folk could glide as fast as 20mph with little effort. With favourable conditions (slope and thermal soaring) they could reach speeds of 40mph, but this would only be sustainable as long as these conditions persist. Slope soaring requires mountains and hills, so mountainous regions would increase their mobility drastically. The upper limit of speed for birds in a dive can vary considerably, and large birds like eagles can reach 200mph, but I doubt our flying humans would be able to tolerate these speeds with their excessively large wingspan, and would struggle to pull out of such a dive without damaging something or doing it very gradually (so high off the ground). In addition, after a dive, they would struggle to regain altitude without a thermal, meaning they would be vulnerable to ground fire after they stuka-dive enemies. Related to this, the maximum altitude of such large birds is often around 5000m, especially if they can hitch lifts on thermals. Bird people would not be able to reach those heights easily, would be able to see very little, have little ability to hit even an army and would take awhile to descend. I think these heights would only be used for long-range scouting and observation. An operating height of about 500m seems much more practical for combat purposes, and if they operated their supply bases from cliff-tops, they would be able to land and take off easily. Flat plains areas would be the regions they expend most energy to operate (gaining altitude) and take the longest to get into position. In fact, it may be impossible for them to take off from flat terrain without a suitable headwind to generate lift. These are the best regions if you want to defend against them or attack. Mountains would be a nightmare to combat them. Attacking on a windless day would also make it more difficult for them.


Next up- power output and energy consumption.

So, again using Argentavis as our best available comparison, this beast requires 3.5 times more energy than it could sustainably output. The flying humans would need even more energy to maintain powered flight, and would likely be even more underpowered for flapping due to it's shared biolgy with arms. So from this, it is safe to assume our birdpeople are gliders, that can only sustain flapping for a brief period (such as takeoff) before suffering fatigue. This makes their combat potential very limited in endurance, unless they simply glide over. There is going to be no agile dives and regaining altitude quickly, at most short dives and dropping payload, before leaving the area to rearm and report back observations. Because of this lack of available power, their flight paths are also going to be considerably more predictable, because they can only sustain erratic course corrections briefly. Therefore firearms could be reasonably effective shooting on-mass.

The power estimated for Argentavis to maintain flight is 600w, but is negligible when gliding or soaring. Our bird people have larger wings and a less efficient aerodynamic weight, although are slightly lighter, so their necessary sustained power could well be considerably higher. I don't have the measurements or algorithms needed to calculate this, but I would not be surprised if it was double. Lets say 1,000w. This is 1,000J per second of active flying, so take-off and combat manouevring is going to be hugely energy intensive- 1 minute of active flying is 60kJ. A normal human requires at least 7,500kJ per day, according to the World Health Organisation, so that is the energy level for basic human metabolism plus some daily activity. Combat flying is likely to add several thousand more kilojoules of energy to that total, maybe even doubling it, if they run a lot of sorties. This is possible to eat, humans can consume 15,000kJ of energy per day, and have to in conditions like cystic fibrosis. This is going to require essentially 50% more rations for actively flying troops per day, and they are going to exhaust themselves pretty quickly in repeated attacks with their low sustainable power threshold. Launching from a clifftop would reduce the energy costs considerably and aid logistics. Simply scouting and remaining at altitude could be far more efficient than walking though, so using the flyers for reconnaisance would be logistically easier.

When laden with a combat load, taking off on the flat would be impossible without assistance (catapult maybe?) and gaining altitude would require thermals and wind with the poor sustainable power. Combat flying would also be drastically affected until munitions are offloaded. Armour at best would be thin cloth (this could prove fatal with rain), but that may be enough to protect against light arrows at the top of their arcs at higher altitudes.


Combat

Active flying largely uses the pectoralis muscle on the anterior chest wall. This muscle also acts on human arms, but is not that involved in throwing or drawing a bow. In gliding flight, it could be used to stabilise the shoulder whilst light weapons are thrown or drawn, but it would be impossible to utilise the back muscles for throwing/drawing a bow without destabilising the flight. It may be possible to accept a temporay drop and then recover into stable flight, but I think in practice gravity will be doing most of the work for projectiles. A dropped soliferrum would still be effective, although a dropped pebble is going to be fairly unimpressive. Medium sized rocks are probably the minimum for useful damage, other than caltrops. The limited munitions due to weight is also an issue, along side balance and storage. Flying with a bag would be disruptive to aerodynamics, so I wouldn't be surprised if such flyers were limited to just an item in each hand, and maybe some small gear on belts. In addition, incendiaries would be pretty much impossible to light on the wing, and fuses could only be lit prior to flying if the supply base is near to the combat. Thankfully, I think these are pretty limited in scope, unless the bird folk develop some kind of working percussion fuse in a suitably lightweight device. If they do, making the fuses unreliable could be a good way to balance this.


Summary

The bird folk could fly, and could eat enough to do it, but their combat capabilities would be limited without nearby resupply, they would tire easily in such conditions, would be very vulnerable without suitable terrain to take off, and their poor ability to dodge and enormous wingspan would make them huge targets if they come within range of the ground folks' weaponry. Huge vulnerable targets, seeing as it wouldn't take much damage to a wing to make it either lame or unable to sustain sufficient lift. Any such injury whilst flying would likely result in a greater proportion of casualties than ground troops too, so the risks are greater. Scouting, communication, observation and spying seem like by far the best options for employing flying troops, as well as ambushes in favourable regions. They would rule the mountains, but fear the plains.

Allright a fairly large number of comments.

1. The idea of a bird human with seperate arms, legs, and wings is completely reasonable. Tool use is literally vital to exploiting intelligence. and it's unlikely arms incorporated into wings would be anywhere near dexterous enough. There's plenty of examples of animals that have had limbs ethier split or merge in their evolutionary history so that part at least is reasonable. We don't see anything like it in nature because advanced tool use outside of humans is very rare, though a few examples have begun to turn up once people started to get past their "dumb animal" preconceptions.

2. Your wing loading figure may actually be too high still, as wing loading and flight speed are connected, and a 20mph+ flight speed could create some real issues taking off.

3. For the same reasons, (high takeoff speed), he legs might be more robust than your imagining. They'd probably still not be suited to distance running, but in short sprints probably quite good.

4. The wing weight is certainly on the low side, the closer to the end of the wing you get the less force it has on it as inner wing area's are transferring all the force from the outer sections in addition to their own.

3. Energy usage is going to vary with flight. Active flight like say a magpie assuming similar efficiencies would be around 10-11kw @ 15mph. A marathon runner uses between 10 and 12 MJ's in between 2 and 3 hours. So your looking at roughly an order of magnitude increase in oxygen intake required, and a much better means of storing large quantities of glucose. The latter is probably more reasonable, an enlarged and modified lifer or a lager secondary liver for the purpose should d it if i'm understanding the stuff i've been reading. The oxygen, thats a bit of an issue, i don't think it's insurmountable, from a purely theoretical standpoint many smaller lungs should allow a significant increase in oxygen uptake compared to humans and i'm sure there are adaptions to increase it even further, the other hard part would be avoiding oxygen narcosis. Again manageable but severely difficult.

I certainly hope that's the case



Wow. I'd come here expecting a bit of discussion on medieval weaponry. I hadn't expected an in-depth analysis of the flight physics of winged humanoids. This is awesome, and also the reason I love this forum

I'll be honest, I hadn't put much thought into their evolution or biology. Flying humanoids were simply a neat fantasy trope I decided to use (and, most likely, not the most biologically implausible one at that). I'll definitely work in some of this when I work up their place in the setting.

Along these lines, that indicates they'd probably focus on producing fairly high-calorie foods. Any suggestions? Primarily plants or meat? I think meat has a higher energy density, but also requires more energy to produce (since you have to feed an animal more than 1 calorie of food to produce 1 calorie of edible meat).

Interesting points about the plains as well. I'd thought about putting the centers of human resistance in a mountainous region; I might change that. Heavy forests, perhaps--negates many of the advantages of the flyers while still causing difficulties for their ground troops. For that matter, heavy forest would make it incredibly difficult for flyers to actually attack their targets, or even see them.

Food would almost have to be majority honey. It's the only calorie dense enough natural thing i can think of and dug up data on that works. If they had better tech they could switch to saturated sugar water with is even more energy dense. Which raises the question of what variety of insect is allowing the to produce multiple tens of kilos of honey a day per head, (thats how great the energy requirements are,. we'd probably poison ourselves if we tried to eat somthing like that in such quantities).

Also what plants are those insects getting the material, (presumably nectar), to make honey from? Theys have t be big, abundant and produce enormous quantities of nectar nearly year round. That would likely limit them to near year round sunny climates unless they reguarly migrated on the wing.

[Clistenes]

I find it very surprising too. I wonder if they would be able to make such efficient darts in a medieval tech setting. Flying at 1000m altitude and dropping 50 of those each whilst travelling over a moving convoy could certainly cause some casualties even with the low accuracy. At least a great harassment method.

It seems that, in the tests, the flechettes where released from planes that were flying at very low altitude, but at high speed... I wonder if the lethality of the projectiles was due to the speed of the plane rather than to gravity itself (the flechettes would start their flight at high speed already...)

[Brother Oni]

A normal human requires at least 7,500kJ per day, according to the World Health Organisation, so that is the energy level for basic human metabolism plus some daily activity. Combat flying is likely to add several thousand more kilojoules of energy to that total, maybe even doubling it, if they run a lot of sorties. This is possible to eat, humans can consume 15,000kJ of energy per day, and have to in conditions like cystic fibrosis.

7500kJ/day is only about 1800 Calories, which is very low for an active individual. I'll have to do more digging on the processing rate of people, however CF sufferers can only eat that many calories because the vast majority of isn't absorbed due to their disease condition and passes through undigested.

Along these lines, that indicates they'd probably focus on producing fairly high-calorie foods. Any suggestions? Primarily plants or meat? I think meat has a higher energy density, but also requires more energy to produce (since you have to feed an animal more than 1 calorie of food to produce 1 calorie of edible meat).

Definitely meat and fat rich diets (see my comment to Carl below).

Food would almost have to be majority honey. It's the only calorie dense enough natural thing i can think of and dug up data on that works. If they had better tech they could switch to saturated sugar water with is even more energy dense. Which raises the question of what variety of insect is allowing the to produce multiple tens of kilos of honey a day per head, (thats how great the energy requirements are,. we'd probably poison ourselves if we tried to eat somthing like that in such quantities).

Actually honey is mostly carbohydrates, which isn't that energy dense - you're looking at ~3 Calories (~12.6kJ) per gram. Fat, especially processed, is far more energy dense - rendered pig fat (lard) is ~9 Calories (37.6kJ) per gram.

Honey is a lot more bioavailable though, which would be useful for immediate actions, but for long term diet, a meat and fat heavy diet would be required.
One side effect of such a diet would be long rest periods to digest such an energy rich diet - take a look at the activity cycles of lions and other obligate carnivores as an example.

I suppose this could tie in with a more Mediterranean lifestyle for our flying humanoids, with long afternoon siestas after lunch.

[Haighus]

I certainly hope that's the case



Wow. I'd come here expecting a bit of discussion on medieval weaponry. I hadn't expected an in-depth analysis of the flight physics of winged humanoids. This is awesome, and also the reason I love this forum

I'll be honest, I hadn't put much thought into their evolution or biology. Flying humanoids were simply a neat fantasy trope I decided to use (and, most likely, not the most biologically implausible one at that). I'll definitely work in some of this when I work up their place in the setting.

Along these lines, that indicates they'd probably focus on producing fairly high-calorie foods. Any suggestions? Primarily plants or meat? I think meat has a higher energy density, but also requires more energy to produce (since you have to feed an animal more than 1 calorie of food to produce 1 calorie of edible meat).

Interesting points about the plains as well. I'd thought about putting the centers of human resistance in a mountainous region; I might change that. Heavy forests, perhaps--negates many of the advantages of the flyers while still causing difficulties for their ground troops. For that matter, heavy forest would make it incredibly difficult for flyers to actually attack their targets, or even see them.

Well, it is an area I am able to make some more detailed analysis in, so I decided to put in some research :) Heavy forest would likely be the best terrain for avoiding them- such a huge wingspan would be a liability in forests, and they'd have very poor visibility. Plains and deserts would be next best. Coasts and mountains are the most in favour of the flyers. I am increasingly seeing them as being ideally like flying Incas, so that may be a cool place to look for ideas. The Incas also venerated the Andean condor, so there is some cool imagery that could be drawn from them. Incas also had very intensive mountainous food production, which brings me on to my next point about energy intake. See below.

Allright a fairly large number of comments.

1. The idea of a bird human with seperate arms, legs, and wings is completely reasonable. Tool use is literally vital to exploiting intelligence. and it's unlikely arms incorporated into wings would be anywhere near dexterous enough. There's plenty of examples of animals that have had limbs ethier split or merge in their evolutionary history so that part at least is reasonable. We don't see anything like it in nature because advanced tool use outside of humans is very rare, though a few examples have begun to turn up once people started to get past their "dumb animal" preconceptions.

2. Your wing loading figure may actually be too high still, as wing loading and flight speed are connected, and a 20mph+ flight speed could create some real issues taking off.

3. For the same reasons, (high takeoff speed), he legs might be more robust than your imagining. They'd probably still not be suited to distance running, but in short sprints probably quite good.

4. The wing weight is certainly on the low side, the closer to the end of the wing you get the less force it has on it as inner wing area's are transferring all the force from the outer sections in addition to their own.

3. Energy usage is going to vary with flight. Active flight like say a magpie assuming similar efficiencies would be around 10-11kw @ 15mph. A marathon runner uses between 10 and 12 MJ's in between 2 and 3 hours. So your looking at roughly an order of magnitude increase in oxygen intake required, and a much better means of storing large quantities of glucose. The latter is probably more reasonable, an enlarged and modified lifer or a lager secondary liver for the purpose should d it if i'm understanding the stuff i've been reading. The oxygen, thats a bit of an issue, i don't think it's insurmountable, from a purely theoretical standpoint many smaller lungs should allow a significant increase in oxygen uptake compared to humans and i'm sure there are adaptions to increase it even further, the other hard part would be avoiding oxygen narcosis. Again manageable but severely difficult.



Food would almost have to be majority honey. It's the only calorie dense enough natural thing i can think of and dug up data on that works. If they had better tech they could switch to saturated sugar water with is even more energy dense. Which raises the question of what variety of insect is allowing the to produce multiple tens of kilos of honey a day per head, (thats how great the energy requirements are,. we'd probably poison ourselves if we tried to eat somthing like that in such quantities).

Also what plants are those insects getting the material, (presumably nectar), to make honey from? Theys have t be big, abundant and produce enormous quantities of nectar nearly year round. That would likely limit them to near year round sunny climates unless they reguarly migrated on the wing.

From what I was reading, large flyers invariably cannot sustain active flight, so they largely rely on environmental factors- thermals and wind, to maintain and gain altitude. Based on this, the bird people would actually have very low energy needs when gliding, which would be most of their flying, and they would not be able to sustain high energy outputs for long without fatiguing. Gliding basically only requires tilting the wing to adjust to changing wind conditions, and slope soaring and thermals can allow forward propulsion without any additional energy input from the bird. I think with this in mind, they would not need much in the way of additional oxygen capacity, because they are largely gliding and soaring. The altitude of 5,000m is within human physiological limits with some adaptation (people can live up to about 6,000m altitude permanently, and survive up to 8,000m for reasonable periods. Beyond 8,000m is when oxygen deprivation becomes short-term life threatening) Only take off would typically be energy intensive, and usually natural features would help this- even a downward slope of 10 degrees, and a head wind of 5mph is enough for Argentavis to be able to take off easily apparently, so similar conditions wold be needed for our birdpeople. I based the flight speeds off the speeds of actual birds and the big prehistoric bird. Only combat, with the additional manoeuvring needs, would be very energy intensive, and it is possible to eat the amounts of energy I posted above by simply eating more meals per day than is typical for humans. I will go into the foodstuffs themselves below.

In terms of size and morphology, I agree when looking back, I think adding 20% weight and wing span would be reasonable, so more like 80kg with a wingspan of 9m (which s enormous, but still smaller than some pterosaurs). There is no example I know of of a vertebrate from amphibians onwards which has more than 4 limbs. This would be a massive change. The way that bat wings work would be the most plausible- a flap of skin extending from the arm along the torso. This would allow the arms to be normally functioning too. You make a good point on the legs likely still being good for sprinting, I agree this is likely. Long distance endurance would be lacking, but then long distance flying is what they will do best.

7500kJ/day is only about 1800 Calories, which is very low for an active individual. I'll have to do more digging on the processing rate of people, however CF sufferers can only eat that many calories because the vast majority of isn't absorbed due to their disease condition and passes through undigested.



Definitely meat and fat rich diets (see my comment to Carl below).



Actually honey is mostly carbohydrates, which isn't that energy dense - you're looking at ~3 Calories (~12.6kJ) per gram. Fat, especially processed, is far more energy dense - rendered pig fat (lard) is ~9 Calories (37.6kJ) per gram.

Honey is a lot more bioavailable though, which would be useful for immediate actions, but for long term diet, a meat and fat heavy diet would be required.
One side effect of such a diet would be long rest periods to digest such an energy rich diet - take a look at the activity cycles of lions and other obligate carnivores as an example.

I suppose this could tie in with a more Mediterranean lifestyle for our flying humanoids, with long afternoon siestas after lunch.

CF sufferers get dietary supplements containing pancreatic enzymes to improve their digestion and absorption of food. The main reason they eat 50% more calories than a typical human should is because of the massive metabolic demands of excessive mucous production and constant laboured breathing and coughing. Active breathing is very energy intensive, so it is one of the reasons people loose weight so quickly when they forced to breath heavy for extended periods.

The 1,800 calories what WHO suggests is the lower limit for a human to survive adequately. This is basically the costs of simply living, plus some activity. I was using it as a baseline for what the bird humans would need if they just lounged around all day. Normal recommended daily intake is about 10,000kJ, so 25% more. CF sufferers eat 50% more than that (ideally). I actually think our bird people would only need about the same intake as normal humans with typical gliding activities, it really is amazingly efficient. Only combat would require more.

Having said this, I agree that meat and fat (and alcohol... It is better than protein and only slightly worse than fat!) are the most energy dense foods. Based on their ideal mountainous location, I think their food production would be similar to the Incas. This would be intensive terraced agriculture to make the most of available terrain, with carbohydrate rich foods like potatoes and proein rich foods like beans, and large scale animal husbandry of creatures like goats, sheep and llamas, which also produce milk and (importantly) butter. Butter is incredibly energy dense with at least 80% fat content, so would be very useful for feeding campaigning armies in intensive combat. It would be most useful in cold conditions were it doesn't perish quickly of course. The Incas actually operated a very sophisticated food production system, with research "labs" to develop new varieties of potatoes and to domesticate new species. Very interesting stuff. I think this could be one of the key advantages of the bird person empire- advanced food production to support a large population of large flyers, which usually have a low population density.

[Brother Oni]

CF sufferers get dietary supplements containing pancreatic enzymes to improve their digestion and absorption of food. The main reason they eat 50% more calories than a typical human should is because of the massive metabolic demands of excessive mucous production and constant laboured breathing and coughing. Active breathing is very energy intensive, so it is one of the reasons people loose weight so quickly when they forced to breath heavy for extended periods.

Looking at some papers, the increased energy expenditure of CF sufferers is only about 10% more than average, but I concede that any physical activity would cause that to increase exponentially.

Having said this, I agree that meat and fat (and alcohol... It is better than protein and only slightly worse than fat!) are the most energy dense foods. Based on their ideal mountainous location, I think their food production would be similar to the Incas. This would be intensive terraced agriculture to make the most of available terrain, with carbohydrate rich foods like potatoes and proein rich foods like beans, and large scale animal husbandry of creatures like goats, sheep and llamas, which also produce milk and (importantly) butter. Butter is incredibly energy dense with at least 80% fat content, so would be very useful for feeding campaigning armies in intensive combat. It would be most useful in cold conditions were it doesn't perish quickly of course. The Incas actually operated a very sophisticated food production system, with research "labs" to develop new varieties of potatoes and to domesticate new species. Very interesting stuff. I think this could be one of the key advantages of the bird person empire- advanced food production to support a large population of large flyers, which usually have a low population density.

Running with the Incan aesthetic even more, it would give a good reason for their stepped pyramids - if they were living quarters as well, it would make it easier for the flyers to take off, with the highest social rank people living towards the top and the slaves or lowest ranked people living on the ground floor tier.

[rs2excelsior]

Well, it is an area I am able to make some more detailed analysis in, so I decided to put in some research :) Heavy forest would likely be the best terrain for avoiding them- such a huge wingspan would be a liability in forests, and they'd have very poor visibility. Plains and deserts would be next best. Coasts and mountains are the most in favour of the flyers. I am increasingly seeing them as being ideally like flying Incas, so that may be a cool place to look for ideas. The Incas also venerated the Andean condor, so there is some cool imagery that could be drawn from them. Incas also had very intensive mountainous food production, which brings me on to my next point about energy intake. See below.

...

Having said this, I agree that meat and fat (and alcohol... It is better than protein and only slightly worse than fat!) are the most energy dense foods. Based on their ideal mountainous location, I think their food production would be similar to the Incas. This would be intensive terraced agriculture to make the most of available terrain, with carbohydrate rich foods like potatoes and proein rich foods like beans, and large scale animal husbandry of creatures like goats, sheep and llamas, which also produce milk and (importantly) butter. Butter is incredibly energy dense with at least 80% fat content, so would be very useful for feeding campaigning armies in intensive combat. It would be most useful in cold conditions were it doesn't perish quickly of course. The Incas actually operated a very sophisticated food production system, with research "labs" to develop new varieties of potatoes and to domesticate new species. Very interesting stuff. I think this could be one of the key advantages of the bird person empire- advanced food production to support a large population of large flyers, which usually have a low population density.

Running with the Incan aesthetic even more, it would give a good reason for their stepped pyramids - if they were living quarters as well, it would make it easier for the flyers to take off, with the highest social rank people living towards the top and the slaves or lowest ranked people living on the ground floor tier.

I like the idea of an Incan aesthetic. Unfortunately I don't know all that much about the Incas. Off to do some research! Again, thanks for the discussion, everyone. Lots of really helpful stuff here.

[Haighus]

Looking at some papers, the increased energy expenditure of CF sufferers is only about 10% more than average, but I concede that any physical activity would cause that to increase exponentially.



Running with the Incan aesthetic even more, it would give a good reason for their stepped pyramids - if they were living quarters as well, it would make it easier for the flyers to take off, with the highest social rank people living towards the top and the slaves or lowest ranked people living on the ground floor tier.

Oh, fair enough, I thought it was larger. That means they don't digest 40% of the extra calories. Hmm, perhaps 50% extra calories may be too much for a human to digest without constant grazing.

Oooh I like the pyramid idea. That is a really interesting concept. Sun temples take on a whole new aspect with their importance for thermals and flying too.

[Max_Killjoy]

Not sure if it's come up in these discussions since we jumped threads, but I would note again that much of the power for flight comes from the chest and back muscles of birds, rather than from muscles in the wings themselves. Thus the deep chests and large "cuts of meat" therefrom even on domestic meat birds that barely ever fly.

A winged humanoid capable of flight would likely have a significantly different torso build for the same biomechanical reasons.

[Haighus]

Not sure if it's come up in these discussions since we jumped threads, but I would note again that much of the power for flight comes from the chest and back muscles of birds, rather than from muscles in the wings themselves. Thus the deep chests and large "cuts of meat" therefrom even on domestic meat birds that barely ever fly.

A winged humanoid capable of flight would likely have a significantly different torso build for the same biomechanical reasons.

I agree, based on what I've read (and discussed above), you would have a slender humanoid, with a massively bulky torso (17% of the weight in the torso, which would be about 15kg of 80kg in my modified theoretical), and really huge wings (9m wingspan), which dwarf the rest of the body in size (but not weight). I also suspect the head and neck would be structured a bit differently, to be more streamlined whilst flying and give a more forward looking head position.

[spineyrequiem]

Depending on how much you're willing to sacrifice ground ability I think you could trim off a bit more leg weight. According to this legs are about 35% of body weight. Reduce that by two thirds and our 70kg man becomes around 52kg. Obviously in this case they'd either have to waddle slowly or wingwalk, but hey, you've got to make some sacrifices. We could also take off the weight of the arms as those're being replaced, but I'm inclined not to so you can factor in the extra weight from flight muscles. 70kg also seems pretty high as an average weight, I'd guess it's based around a 6'-ish man. If we instead base it on the Incas (just to rip off a bit more of their civilisation), with an average male height of 5'2", we get a weight of about 54.5 kg, or 41kg with shorter legs. Note that my maths is not even close to accurate, but it does make for a very slightly more reasonable wingspan.

[Haighus]

Depending on how much you're willing to sacrifice ground ability I think you could trim off a bit more leg weight. According to this legs are about 35% of body weight. Reduce that by two thirds and our 70kg man becomes around 52kg. Obviously in this case they'd either have to waddle slowly or wingwalk, but hey, you've got to make some sacrifices. We could also take off the weight of the arms as those're being replaced, but I'm inclined not to so you can factor in the extra weight from flight muscles. 70kg also seems pretty high as an average weight, I'd guess it's based around a 6'-ish man. If we instead base it on the Incas (just to rip off a bit more of their civilisation), with an average male height of 5'2", we get a weight of about 54.5 kg, or 41kg with shorter legs. Note that my maths is not even close to accurate, but it does make for a very slightly more reasonable wingspan.

Well, instead of replacing the arms, our humanoids have arms AND wings, which adds a degree of weight. They are supposed to be roughly analogous to humans, but with flying abilities (thus allowing them to operate weapons and fly simultaneously). If you look at my calculations on the previous page, and near the top of this page, I started with a lightweight 50kg human, and added ~20% more weight for flying muscles, plus the weight of the wings. That came out as roughly 80kg altogether.

If we start adjusting the bodies to become more adapted for flying, we loose some of the human capabilities. Depends on what the original poster actually wants for their flying humans really, but I tried to get as close as possible to a plausible human with wings scenario.

[Clistenes]

It seems that, in the tests, the flechettes where released from planes that were flying at very low altitude, but at high speed... I wonder if the lethality of the projectiles was due to the speed of the plane rather than to gravity itself (the flechettes would start their flight at high speed already...)

I have re-read the Wikipedia's Lazy Dog entry... and I have doubts.

-The flechette weighs 13 gr. only, around the same some .30-06 Springfield bullets. That's very little for a kinetic weapon...

-The planes that released them in the tests were flying at an altitude of around 23 meters, and were flying at a speed of 400 knots (740.8 km/h = 205.78 m/s).

-The speed of an object released from 23 meters would be around 21 m/s, but that's just vertical speed. The flechettes conserved the horizontal speed of the plane, of around 205.78 m/s. Most of the energy they carried came mostly form the plane's own speed.

-Using the Pythagorean theorem, the speed of the flechette was, discarding air resistance, of around 206.85 m/s...

-That means the flechettes carried a kinetic energy of around 556.23 Joules.

-By comparision, a Winchester .45 ACP cartridge carries packs a kinetic energy of around 483 to 796 Joules, and a 9×19mm Parabellum cartridge of 481 to 588 Joules. 556.23 Joules is still pretty deadly, though...

But my point is, most of the kinetic energy carried by the flechette came from the speed of the plane, not from gravity, so the Lazy Dog tests aren't relevant for our current thought experiment.

I have sought information about WWI kinetic bombardment flechettes, and they were 60 grams of weight, pencil-shaped, and were thrown from a high altitude. That sounds more plausible for our flying freaks...

[Brother Oni]

Oh, fair enough, I thought it was larger. That means they don't digest 40% of the extra calories. Hmm, perhaps 50% extra calories may be too much for a human to digest without constant grazing.

Even with additional pancreatic enzymes to pre-digest their food, it's very difficult for nutrients to be absorbed through the thick mucus in their intestines - it's most likely digested, it simply doesn't get into their system in the time it passes through their GI tract. I once attended a talk by a CF sufferer on her average day - the enzymes you mentioned was one she always took as she otherwise got extremely bad diarrhoea (she was on something like 28 different medications every day and after a while, she just stopped bothering to take all of them as all those treatments took so long to do, it detracted more from her quality of life than she gained - nebulisers were the worst as they could take up to an hour from setup to finishing washing up afterwards; imagine taking that three times a day).

Back on topic, the highest calorie intakes I know about are for activities in the extreme cold; living in the Antarctic can require from 2750 Calories when working inside buildings to 6500 Calories when manhandling sleds (11.5MJ to 27.2MJ). Royal Marines during Arctic survival training can consume up to 8000 Calories a day (33.5MJ).

While all those extra calories are pretty much all going to thermogenesis rather than aerobic exercise, it does give an upper limit of calorific intake and energy expenditure without turning into a walking blubber ball.

[Carl]

7500kJ/day is only about 1800 Calories, which is very low for an active individual. I'll have to do more digging on the processing rate of people, however CF sufferers can only eat that many calories because the vast majority of isn't absorbed due to their disease condition and passes through undigested.



Definitely meat and fat rich diets (see my comment to Carl below).



Actually honey is mostly carbohydrates, which isn't that energy dense - you're looking at ~3 Calories (~12.6kJ) per gram. Fat, especially processed, is far more energy dense - rendered pig fat (lard) is ~9 Calories (37.6kJ) per gram.

Honey is a lot more bioavailable though, which would be useful for immediate actions, but for long term diet, a meat and fat heavy diet would be required.
One side effect of such a diet would be long rest periods to digest such an energy rich diet - take a look at the activity cycles of lions and other obligate carnivores as an example.

I suppose this could tie in with a more Mediterranean lifestyle for our flying humanoids, with long afternoon siestas after lunch.

Yes and no.

First my understanding is that outside of late summer/autumn in climates where animals hibernate the fat to meat ratio of wild game is quite poor, this severely curtails the energy density of meat.

Second, meat is fairly energy dense but not anywhere near as volume dense, this limits meal size which limits daily intake.

Third, meat as you noted takes a long time to digest whilst honey being mostly sugars processes faster from what i understand.

That dosen;t mean i'd see bird people as pure honey eater,s just that it would be the most critical part of their diet IMO as it wold provide quick easy fuel. fat risch game meat would probably be more of the "extra food and might well constitute a delicacy the way many meats did historically.

Well, it is an area I am able to make some more detailed analysis in, so I decided to put in some research :) Heavy forest would likely be the best terrain for avoiding them- such a huge wingspan would be a liability in forests, and they'd have very poor visibility. Plains and deserts would be next best. Coasts and mountains are the most in favour of the flyers. I am increasingly seeing them as being ideally like flying Incas, so that may be a cool place to look for ideas. The Incas also venerated the Andean condor, so there is some cool imagery that could be drawn from them. Incas also had very intensive mountainous food production, which brings me on to my next point about energy intake. See below.

From what I was reading, large flyers invariably cannot sustain active flight, so they largely rely on environmental factors- thermals and wind, to maintain and gain altitude. Based on this, the bird people would actually have very low energy needs when gliding, which would be most of their flying, and they would not be able to sustain high energy outputs for long without fatiguing. Gliding basically only requires tilting the wing to adjust to changing wind conditions, and slope soaring and thermals can allow forward propulsion without any additional energy input from the bird. I think with this in mind, they would not need much in the way of additional oxygen capacity, because they are largely gliding and soaring. The altitude of 5,000m is within human physiological limits with some adaptation (people can live up to about 6,000m altitude permanently, and survive up to 8,000m for reasonable periods. Beyond 8,000m is when oxygen deprivation becomes short-term life threatening) Only take off would typically be energy intensive, and usually natural features would help this- even a downward slope of 10 degrees, and a head wind of 5mph is enough for Argentavis to be able to take off easily apparently, so similar conditions wold be needed for our birdpeople. I based the flight speeds off the speeds of actual birds and the big prehistoric bird. Only combat, with the additional manoeuvring needs, would be very energy intensive, and it is possible to eat the amounts of energy I posted above by simply eating more meals per day than is typical for humans. I will go into the foodstuffs themselves below.

In terms of size and morphology, I agree when looking back, I think adding 20% weight and wing span would be reasonable, so more like 80kg with a wingspan of 9m (which s enormous, but still smaller than some pterosaurs). There is no example I know of of a vertebrate from amphibians onwards which has more than 4 limbs. This would be a massive change. The way that bat wings work would be the most plausible- a flap of skin extending from the arm along the torso. This would allow the arms to be normally functioning too. You make a good point on the legs likely still being good for sprinting, I agree this is likely. Long distance endurance would be lacking, but then long distance flying is what they will do best.

The problem is i'm not sure a humanoid non-active flyer could evolve. You said it yourself they're going to be poor diving hunters and their size makes that worse s they're more visible to potential prey. That means wings would be far less useful to them than the arms, so why do they have wings still evolutionary speaking. An active flyer has a lot more ways to benefit from wings than a passive one which makes them more likely to keep their wings rather than ditch them for the tool utility. There's also the collory issue that passive flight is a fairly slow hunting technique. On a bird that works. On a Bird man with a brain it may be a serious issue as the brain uses quite a bit of power. Not as much as active flight, (in fact nowhere near), but enough that it may make passive flight based hunting or long distance foraging unworkable.

Also since we're talking about military applications active flyers are far more useful.

The reason large birds are passive fliers mostly comes down to the aerobic exercise limit, they just can't take in enough oxygen to handle the energy expenditure required. Thats the real headache with bird people.

None of thats to say they won't use passive flight in a lot of situations, and long distance travel will likely be somthing of a combination, short periods of active flight interspaced by long glides. But i can't see them working evolutionary as pure passive fliers.

[Haighus]

Even with additional pancreatic enzymes to pre-digest their food, it's very difficult for nutrients to be absorbed through the thick mucus in their intestines - it's most likely digested, it simply doesn't get into their system in the time it passes through their GI tract. I once attended a talk by a CF sufferer on her average day - the enzymes you mentioned was one she always took as she otherwise got extremely bad diarrhoea (she was on something like 28 different medications every day and after a while, she just stopped bothering to take all of them as all those treatments took so long to do, it detracted more from her quality of life than she gained - nebulisers were the worst as they could take up to an hour from setup to finishing washing up afterwards; imagine taking that three times a day).

Back on topic, the highest calorie intakes I know about are for activities in the extreme cold; living in the Antarctic can require from 2750 Calories when working inside buildings to 6500 Calories when manhandling sleds (11.5MJ to 27.2MJ). Royal Marines during Arctic survival training can consume up to 8000 Calories a day (33.5MJ).

While all those extra calories are pretty much all going to thermogenesis rather than aerobic exercise, it does give an upper limit of calorific intake and energy expenditure without turning into a walking blubber ball.

CF does have a terrible quality of life in many ways- there is definitely a cost to the increased life expectancy nowadays.
Hmm, I believe artic explorers essentially pull sleds of butter too. Those higher end figures will be operating at a loss though, they won't be able to sustain that for more than a few weeks at most before starving/freezing, and will lose weight over this time. Cyclists in the Tour de France essentially eat optimum dietary intake for maximal short term energy input, and they lose weight and muscle mass over three weeks.

Yes and no.

First my understanding is that outside of late summer/autumn in climates where animals hibernate the fat to meat ratio of wild game is quite poor, this severely curtails the energy density of meat.

Second, meat is fairly energy dense but not anywhere near as volume dense, this limits meal size which limits daily intake.

Third, meat as you noted takes a long time to digest whilst honey being mostly sugars processes faster from what i understand.

That dosen;t mean i'd see bird people as pure honey eater,s just that it would be the most critical part of their diet IMO as it wold provide quick easy fuel. fat risch game meat would probably be more of the "extra food and might well constitute a delicacy the way many meats did historically.



The problem is i'm not sure a humanoid non-active flyer could evolve. You said it yourself they're going to be poor diving hunters and their size makes that worse s they're more visible to potential prey. That means wings would be far less useful to them than the arms, so why do they have wings still evolutionary speaking. An active flyer has a lot more ways to benefit from wings than a passive one which makes them more likely to keep their wings rather than ditch them for the tool utility. There's also the collory issue that passive flight is a fairly slow hunting technique. On a bird that works. On a Bird man with a brain it may be a serious issue as the brain uses quite a bit of power. Not as much as active flight, (in fact nowhere near), but enough that it may make passive flight based hunting or long distance foraging unworkable.

Also since we're talking about military applications active flyers are far more useful.

The reason large birds are passive fliers mostly comes down to the aerobic exercise limit, they just can't take in enough oxygen to handle the energy expenditure required. Thats the real headache with bird people.

None of thats to say they won't use passive flight in a lot of situations, and long distance travel will likely be somthing of a combination, short periods of active flight interspaced by long glides. But i can't see them working evolutionary as pure passive fliers.

No flyer of this kind could evolve full stop anyway, so I'm handwaving that to get close to a model that works for the OP's specifications. Theoretically, what we have so far could be genetically engineered, and function. It is one of those examples that is useful as a fully formed entity, but couldn't get there through an evolutionary path.

There are no known examples of active flyers this large, that could sustain active flight, so I went with passive overall, and short term active. This also gives the flyers a palpable weakness, that stops them being as dominating as they could otherwise be. I reckon the passive flying for large birds also comes down to diminishing returns on increased muscle mass against increasing weight- the huge bird I linked to above was only capable of outputting a third of the power it needed to sustain active flight. That isn't just an aerobic limit, but a literal muscle power limit too.

I don't think the human brain will be a huge problem*, because humans are already adapted to consuming that much energy. It does mean a passive bird person is going to use more energy than a passive bird with a smaller brain, but the advantages of being smart is probably going to outweigh that.

*As a note related to this, humans have a degree of obligate carbohydrate consumption- they die without any glucose at all (brain and red blood cells being the most important requirers of glucose). This means they will need to eat some carbs ideally, although protein can substitute for carbs (it isn't ideal for this).

[rs2excelsior]

I agree about winged humanoids not really being practically able to evolve. The skeletal structure alone to accommodate a double-shoulder would be...implausible to say the least. And yet, they're a fantasy trope I decided to run with, biology be damned. I mean, you can have house-sized, double-shouldered dragons flying around without a care in the world.

Regarding the energy density of meat, they will definitely have domesticated animals, so the fat levels of wild game isn't really an issue. They can raise animals which are fattier to suit their needs.

Also, for anyone who might be interested to see where this goes, here is where I'm developing my ideas further. It's very much a rough draft--much of the detail is still open ended and I haven't posted everything I have nailed down yet--but I'm planning on continuing to flesh things out as I go. [/shameless plug]

[Carl]

CF does have a terrible quality of life in many ways- there is definitely a cost to the increased life expectancy nowadays.
Hmm, I believe artic explorers essentially pull sleds of butter too. Those higher end figures will be operating at a loss though, they won't be able to sustain that for more than a few weeks at most before starving/freezing, and will lose weight over this time. Cyclists in the Tour de France essentially eat optimum dietary intake for maximal short term energy input, and they lose weight and muscle mass over three weeks.


No flyer of this kind could evolve full stop anyway, so I'm handwaving that to get close to a model that works for the OP's specifications. Theoretically, what we have so far could be genetically engineered, and function. It is one of those examples that is useful as a fully formed entity, but couldn't get there through an evolutionary path.

There are no known examples of active flyers this large, that could sustain active flight, so I went with passive overall, and short term active. This also gives the flyers a palpable weakness, that stops them being as dominating as they could otherwise be. I reckon the passive flying for large birds also comes down to diminishing returns on increased muscle mass against increasing weight- the huge bird I linked to above was only capable of outputting a third of the power it needed to sustain active flight. That isn't just an aerobic limit, but a literal muscle power limit too.

I don't think the human brain will be a huge problem*, because humans are already adapted to consuming that much energy. It does mean a passive bird person is going to use more energy than a passive bird with a smaller brain, but the advantages of being smart is probably going to outweigh that.

*As a note related to this, humans have a degree of obligate carbohydrate consumption- they die without any glucose at all (brain and red blood cells being the most important requirers of glucose). This means they will need to eat some carbs ideally, although protein can substitute for carbs (it isn't ideal for this).

It's very unlikely somthing like this could evolve, but if it's physically possibble the it could actually evolve. As i pointed out previously evolution is full of creatures where limbs joined or separated limbs at some point in their evolution so having arms seperate out from the wings is a long way from impossible. The odds against it are fairly long, but it's not outright impossible.

The problem i have with passive flight is thats it's simply incompatible with intelligance when you get right down to it. Passive flight is an evolutionary choice made because in general large bird active flight is simply more energy intensive than any naturally occurring environment, (on earth, it's not set in stone that a sufficiently energy rich environment could not exist, though it would likely have many other implications), can provide for. Since they can't get enough food they don't evolve, (or lose if they started out smaller), any active flight features, and as nature continues to select for passive flight this reinforces itself emphasising reduction of any features that make it less effective. And thats where the high energy cost of a brain becomes an issue. Bigger brains with bigger energy costs harm passive flight as a successful survival strategy so it actually would result in selection against intelligance without another competing factor. And the limited food selection afforded by passive flight would tend to select against tool use, (though thats not definitive, it merely reduces the range of avenues by which it could develop), and especially the large ranges involved would tend to limit population density which would select against communication.

The more i think about it the most sensible evolutionary path is soe smaller bird that preys on a primary pry that needs more manipulation than beak and talons alone would provide result in use of the wing as a pinning tool. This could then develop into wingtip ips of a different design, which could allow for other wing uses which could develop wing tip hands and eventual splitting of the limb. If they're allready communal this could reasonably be expected to create a positive benefit of more intelligance and that would likely lead to steady increases in absolute size to support the more advanced brain structure.

I''m not sure what the point of the * comment was though. Yes humans need carb's, duh. That doesn't make honey invalid since it's >80% carbs by weight, in fact depending on the honey it's between 15% and 35% pure glucose by weight, (most of the rest is fructose, another sugar type carbohydrate directly absorbed by the blood). That said some thinking on the evolution side makes me think Nuts, sweet fruits, and of course meats would be more important secondary foods alongside than i'd first assumed. (In the same way most humans eat a lot of meats, but still eat fruit and veg alongside to varying degrees). Having a wider array of food sources is very useful to a communal species because it helps larger groups survive from the same hunting/foraging range area. If there's suitable large scale honey producing insects aroudn it's possible, perhaps even probable that the nectar producing plants would be larger which might leads to Nectar being a viable thing to gather direct as well. Would make for interesting agriculture.

[Carl]

I agree about winged humanoids not really being practically able to evolve. The skeletal structure alone to accommodate a double-shoulder would be...implausible to say the least. And yet, they're a fantasy trope I decided to run with, biology be damned. I mean, you can have house-sized, double-shouldered dragons flying around without a care in the world.

Regarding the energy density of meat, they will definitely have domesticated animals, so the fat levels of wild game isn't really an issue. They can raise animals which are fattier to suit their needs.

Also, for anyone who might be interested to see where this goes, here is where I'm developing my ideas further. It's very much a rough draft--much of the detail is still open ended and I haven't posted everything I have nailed down yet--but I'm planning on continuing to flesh things out as I go. [/shameless plug]

Forgot to quote this above because reasons. DoH!

Having domesticated animals that can be as fatty as they like won't make it a primary food source. meat is such a big source for humans because thanks to our hunter gatherer history we went through a sage where wild meat was a major source. In short both in terms of our physiology and subtle hand me down psychological stuff where inclined towards high meat intake. But bird people won't necessarily have that. Anyway gotta go got some more comments on ways a passive flight model could work for bird people but need to go out and then sleep so probably 12 hours or so from now at the earliest.

[Brother Oni]

That dosen;t mean i'd see bird people as pure honey eater,s just that it would be the most critical part of their diet IMO as it wold provide quick easy fuel. fat risch game meat would probably be more of the "extra food and might well constitute a delicacy the way many meats did historically.

I disagree - while I concede that volume for volume, honey is more energy dense (~1.4 g/ml compared to 0.6-0.9 g/ml for meat) trying to keep down that much honey would both be difficult and poor for glycemic control (take a look at sugar-crashed children after Halloween).

I don't disagree that honey would be good for a quick fix and indeed a meal of mead could form part of their cultural pre-battle preparations, I don't think subsisting primarily from honey is efficient nor good for long term health.

Bear in mind that animals with a heavy meat/fat heavy diet tend to sleep or nap more, thus lowering their daily metabolic requirements. Daily activity and hence energy expenditure isn't spread evenly throughout the day, so quick energy spikes from honey may not be necessary. This also isn't counting the additional water intake due to the high glucose/fructose content of honey as it's turned into glycogen as an intermediary before storage as fat.

I''m not sure what the point of the * comment was though. Yes humans need carb's, duh. That doesn't make honey invalid since it's >80% carbs by weight, in fact depending on the honey it's between 15% and 35% pure glucose by weight, (most of the rest is fructose, another sugar type carbohydrate directly absorbed by the blood). That said some thinking on the evolution side makes me think Nuts, sweet fruits, and of course meats would be more important secondary foods alongside than i'd first assumed. (In the same way most humans eat a lot of meats, but still eat fruit and veg alongside to varying degrees).

Actually while we have evolved to primarily burn carbohydrates, we technically don't need it as both protein and fats can be burnt to provide energy (fats undergo lipolysis and the constituents are chucked into the Kreb's Cycle, proteins can either be processed into pyruvate like fats or just burnt as ketone bodies).

There's a growing hypothesis that humans brains developed because we invented cooking, thus raising the bioavailability of calories from the foodstuffs we ate and providing the additional calories required.

[Haighus]

It's very unlikely somthing like this could evolve, but if it's physically possibble the it could actually evolve. As i pointed out previously evolution is full of creatures where limbs joined or separated limbs at some point in their evolution so having arms seperate out from the wings is a long way from impossible. The odds against it are fairly long, but it's not outright impossible.

The problem i have with passive flight is thats it's simply incompatible with intelligance when you get right down to it. Passive flight is an evolutionary choice made because in general large bird active flight is simply more energy intensive than any naturally occurring environment, (on earth, it's not set in stone that a sufficiently energy rich environment could not exist, though it would likely have many other implications), can provide for. Since they can't get enough food they don't evolve, (or lose if they started out smaller), any active flight features, and as nature continues to select for passive flight this reinforces itself emphasising reduction of any features that make it less effective. And thats where the high energy cost of a brain becomes an issue. Bigger brains with bigger energy costs harm passive flight as a successful survival strategy so it actually would result in selection against intelligance without another competing factor. And the limited food selection afforded by passive flight would tend to select against tool use, (though thats not definitive, it merely reduces the range of avenues by which it could develop), and especially the large ranges involved would tend to limit population density which would select against communication.

The more i think about it the most sensible evolutionary path is soe smaller bird that preys on a primary pry that needs more manipulation than beak and talons alone would provide result in use of the wing as a pinning tool. This could then develop into wingtip ips of a different design, which could allow for other wing uses which could develop wing tip hands and eventual splitting of the limb. If they're allready communal this could reasonably be expected to create a positive benefit of more intelligance and that would likely lead to steady increases in absolute size to support the more advanced brain structure.

I''m not sure what the point of the * comment was though. Yes humans need carb's, duh. That doesn't make honey invalid since it's >80% carbs by weight, in fact depending on the honey it's between 15% and 35% pure glucose by weight, (most of the rest is fructose, another sugar type carbohydrate directly absorbed by the blood). That said some thinking on the evolution side makes me think Nuts, sweet fruits, and of course meats would be more important secondary foods alongside than i'd first assumed. (In the same way most humans eat a lot of meats, but still eat fruit and veg alongside to varying degrees). Having a wider array of food sources is very useful to a communal species because it helps larger groups survive from the same hunting/foraging range area. If there's suitable large scale honey producing insects aroudn it's possible, perhaps even probable that the nectar producing plants would be larger which might leads to Nectar being a viable thing to gather direct as well. Would make for interesting agriculture.

I agree with all your points on evolution and intelligence, although I still do not know of any examples of splitting limbs in vertebrates- if you could give some that would be excellent. It could happen, but I think the timespans involved could be enormous. I essentially handwaved it, because it would almost certainly not generate the type of flyer the OP was looking for, but rather something more like a corvid in size- the "angry pixie" mentioned by Galloglaich. Physically possible doesn't necessarily mean evolutionarily plausible, because open there ar insumountable hurdles to reaching a finished, useful evolutionary product.

The * bit was more just personal musings on the topic, than replying to any specific point. I was basically thinking an omnivorous diet would be best. It certainly doesn't rule out honey. I agree with Brother Oni below that honey would be best as a supplement for periods of intensive activity. If we look at athletes for guides on energy intake, complex carbohydrates like starch are better for sustained physical activity, with easily bioavailable sugars used as a top-up during activity. So I think eating rice and potatoes and wheat-based products as general calories, with honey best used as a boost everytime they return from an attack sortie to re-arm and recover energy, or even taking small pots to use when on the wing over long journeys. Would still require a massive honey industry if using for rapid recovery in warfare. This would give them some interesting logistical considerations.

I disagree - while I concede that volume for volume, honey is more energy dense (~1.4 g/ml compared to 0.6-0.9 g/ml for meat) trying to keep down that much honey would both be difficult and poor for glycemic control (take a look at sugar-crashed children after Halloween).

I don't disagree that honey would be good for a quick fix and indeed a meal of mead could form part of their cultural pre-battle preparations, I don't think subsisting primarily from honey is efficient nor good for long term health.

Bear in mind that animals with a heavy meat/fat heavy diet tend to sleep or nap more, thus lowering their daily metabolic requirements. Daily activity and hence energy expenditure isn't spread evenly throughout the day, so quick energy spikes from honey may not be necessary. This also isn't counting the additional water intake due to the high glucose/fructose content of honey as it's turned into glycogen as an intermediary before storage as fat.



Actually while we have evolved to primarily burn carbohydrates, we technically don't need it as both protein and fats can be burnt to provide energy (fats undergo lipolysis and the constituents are chucked into the Kreb's Cycle, proteins can either be processed into pyruvate like fats or just burnt as ketone bodies).

There's a growing hypothesis that humans brains developed because we invented cooking, thus raising the bioavailability of calories from the foodstuffs we ate and providing the additional calories required.

Eating a huge amount of honey can also result in diarrhoea, if you eat beyond the level of sugar that can be absorbed by the gut.

We don't need to eat carbs, although we do need them to survive- fat alone is not sufficient because only the glycerol in triglycerides can be turned into glucose. Fats can be burned directly by most cells as you mention, but the brain can only utilise ketones from fats, and needs at least 30% glucose to function alongside the ketones. Apparently the ability to utilise ketones is unique to human brains as an adaption for having such a large brain, but I have never seen proper evidence supporting this theory. Interesting if true. Red blood cells can only use glucose. This is why overweight diabetics can die of ketoacidosis in hypoglycaemia. Protein can be turned into glucose (well, some amino acids can, not all), but comes with byproducts which make it less desirable than eating some carbs to supplement it. In a starvation state, once glycogen reserves are used up, protein from tissues is used to create glucose for obligate tissues (red blood cells and brain), whilst fats are used to fuel everything else until they are exhausted. Protein is generally the limiting energy supply in starvation, and people who are adequately hydrated but no food intake, loss of protein is what kills them (apparently usually through the diaphragm becoming too weak to sustain breathing and rupturing).

What this means is that a human can live off a low-carbs, high-protein diet, but it isn't ideal, and some carbs are needed to be healthy. Inuits have adapted to a high protein and fat, exclusively meat diet, but they are unusual in this regard, and it doesn't work well for unadapted people. The bird people could be similarly adapted, but I suspect omnivorous feeding habits to be the best for their function.

The cooking thing is awesome. I can see the logic behind the theory.

[Tobtor]

What this means is that a human can live off a low-carbs, high-protein diet, but it isn't ideal, and some carbs are needed to be healthy. Inuits have adapted to a high protein and fat, exclusively meat diet, but they are unusual in this regard, and it doesn't work well for unadapted people. The bird people could be similarly adapted, but I suspect omnivorous feeding habits to be the best for their function.

As you say, Inuit live almost exclusively on meat. So adaptation is relatively simple (compared to the rest of the bird ecology anyway).

In contrast to above suggestions about mountains, I think some ocean-culture is better suited for the bird people. The sea simply provides so much nutrient rich sources of food that it would greatly help the bird people for their higher energy consumption. Also if the were based on island(s) of the coast, they would have a secure homebase, which could explain why the humans does not focus solely on the bird-peoples home territory: Attacking flying creatures living on an Island would be immensely difficult (as hitting ships from above with "fire-bombs" would be devastating for any attacker).

So you could have the bird people living on (mountainous) islands of the coast, who have colonised/occupied the coast, and made coastal humans fight for them. Then you could have more inland humans fighting against this "bird"-empire.

For food you could supplement plant food, with rich marine sources (migratory whales for high fat intake?, otherwise fish, seals, shellfish, eggs of seabirds and so on is easily gathered/hunted). This can easily be combined with "terraced agriculture", used for stable food (and possible fermenting to alcohol or similar for easier consumption of high energy intake).

[Carl]

I disagree - while I concede that volume for volume, honey is more energy dense (~1.4 g/ml compared to 0.6-0.9 g/ml for meat) trying to keep down that much honey would both be difficult and poor for glycemic control (take a look at sugar-crashed children after Halloween).

I don't disagree that honey would be good for a quick fix and indeed a meal of mead could form part of their cultural pre-battle preparations, I don't think subsisting primarily from honey is efficient nor good for long term health.

Bear in mind that animals with a heavy meat/fat heavy diet tend to sleep or nap more, thus lowering their daily metabolic requirements. Daily activity and hence energy expenditure isn't spread evenly throughout the day, so quick energy spikes from honey may not be necessary. This also isn't counting the additional water intake due to the high glucose/fructose content of honey as it's turned into glycogen as an intermediary before storage as fat.



Actually while we have evolved to primarily burn carbohydrates, we technically don't need it as both protein and fats can be burnt to provide energy (fats undergo lipolysis and the constituents are chucked into the Kreb's Cycle, proteins can either be processed into pyruvate like fats or just burnt as ketone bodies).

There's a growing hypothesis that humans brains developed because we invented cooking, thus raising the bioavailability of calories from the foodstuffs we ate and providing the additional calories required.

My main thought with the honey was basically this:

Digestive systems vary from species to species so a digestive system optimized for whatever's best makes sense. That makes the real limitation the size of the stomach sacks, (and the volume pressure this puts on other organs from an evolutionary standpoint). For active flight 1 liter of honey will power just half an hours flight, so they'd need to consume several litters before a multi-hour flight session and then let it digest.With that kind of feeding requirements meats have the problem that a good meal of slowly digested meat might only let them fly for an hour or two each day. How valuable is that going to be evolutionary? You could well see evolution start to select against flight in those circumstances unless flight was absolutely vital in some fashion.

The cooking angle is interesting because there are a number of cooking techniques that can absolutely enhance nutrition of course.

I agree with all your points on evolution and intelligence, although I still do not know of any examples of splitting limbs in vertebrates- if you could give some that would be excellent. It could happen, but I think the timespans involved could be enormous. I essentially handwaved it, because it would almost certainly not generate the type of flyer the OP was looking for, but rather something more like a corvid in size- the "angry pixie" mentioned by Galloglaich. Physically possible doesn't necessarily mean evolutionarily plausible, because open there ar insumountable hurdles to reaching a finished, useful evolutionary product.

The * bit was more just personal musings on the topic, than replying to any specific point. I was basically thinking an omnivorous diet would be best. It certainly doesn't rule out honey. I agree with Brother Oni below that honey would be best as a supplement for periods of intensive activity. If we look at athletes for guides on energy intake, complex carbohydrates like starch are better for sustained physical activity, with easily bioavailable sugars used as a top-up during activity. So I think eating rice and potatoes and wheat-based products as general calories, with honey best used as a boost everytime they return from an attack sortie to re-arm and recover energy, or even taking small pots to use when on the wing over long journeys. Would still require a massive honey industry if using for rapid recovery in warfare. This would give them some interesting logistical considerations.

Eating a huge amount of honey can also result in diarrhoea, if you eat beyond the level of sugar that can be absorbed by the gut.

We don't need to eat carbs, although we do need them to survive- fat alone is not sufficient because only the glycerol in triglycerides can be turned into glucose. Fats can be burned directly by most cells as you mention, but the brain can only utilise ketones from fats, and needs at least 30% glucose to function alongside the ketones. Apparently the ability to utilise ketones is unique to human brains as an adaption for having such a large brain, but I have never seen proper evidence supporting this theory. Interesting if true. Red blood cells can only use glucose. This is why overweight diabetics can die of ketoacidosis in hypoglycaemia. Protein can be turned into glucose (well, some amino acids can, not all), but comes with byproducts which make it less desirable than eating some carbs to supplement it. In a starvation state, once glycogen reserves are used up, protein from tissues is used to create glucose for obligate tissues (red blood cells and brain), whilst fats are used to fuel everything else until they are exhausted. Protein is generally the limiting energy supply in starvation, and people who are adequately hydrated but no food intake, loss of protein is what kills them (apparently usually through the diaphragm becoming too weak to sustain breathing and rupturing).

What this means is that a human can live off a low-carbs, high-protein diet, but it isn't ideal, and some carbs are needed to be healthy. Inuits have adapted to a high protein and fat, exclusively meat diet, but they are unusual in this regard, and it doesn't work well for unadapted people. The bird people could be similarly adapted, but I suspect omnivorous feeding habits to be the best for their function.

The cooking thing is awesome. I can see the logic behind the theory.

Actually physically possibble pretty much does mean evolutionarily possibble. The catch is some things require such far out there factors that as a matter of practise the odds are exceedingly low. The thing is in fiction the odds can be as long as you want, and still come up trumps.


I did say i'd talk about how passive flight might work out. Whilst it's just completely incompatible with what the OP wanted the easiest way would be to make the passive flight pure transport and have them do their hunting and gathering on the ground. I'm not sure what evolutionary pressures precisely could produce such a need for efficient long distance transit but it would also probably look closest to the traditional "winged human" archetype as the heavy groundside work would tend to push for a more human limb set whilst whatever evolutionary pressure needs that excellent long distance efficient movement capability would tend to push the desire to keep the wings, whilst the poor hunting and gathering efficiency of passive flight pushes the need to do hunting and gathering ground side with a body better adapted to it.

[Tobtor]

I did say i'd talk about how passive flight might work out. Whilst it's just completely incompatible with what the OP wanted the easiest way would be to make the passive flight pure transport and have them do their hunting and gathering on the ground. I'm not sure what evolutionary pressures precisely could produce such a need for efficient long distance transit but it would also probably look closest to the traditional "winged human" archetype as the heavy groundside work would tend to push for a more human limb set whilst whatever evolutionary pressure needs that excellent long distance efficient movement capability would tend to push the desire to keep the wings, whilst the poor hunting and gathering efficiency of passive flight pushes the need to do hunting and gathering ground side with a body better adapted to it.

Transport between different "living" quarters could be a reason. Sort of like with of the Draco lizards, which have developed "wing"-like tisue independent of their 4 limps (they use the "wings" to move from tree to tree without going to the bottom of the forrest):

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Draco Volans

These liazards doesn't really have flight (just gliding), but perhaps we could imagine our "bird" people stating out this way and then developing more "flight" ability? Anyway Draco lizards are the closest I have seen to a vertibrae with four limps +"wings".

They could have developed the early flight to move between mountains (or islands with sea cliffs), as a way of moving about. The gradually improved it with more powered flight to use in hunting/fighting?

[Brother Oni]

My main thought with the honey was basically this:

Digestive systems vary from species to species so a digestive system optimized for whatever's best makes sense. That makes the real limitation the size of the stomach sacks, (and the volume pressure this puts on other organs from an evolutionary standpoint). For active flight 1 liter of honey will power just half an hours flight, so they'd need to consume several litters before a multi-hour flight session and then let it digest.With that kind of feeding requirements meats have the problem that a good meal of slowly digested meat might only let them fly for an hour or two each day. How valuable is that going to be evolutionary? You could well see evolution start to select against flight in those circumstances unless flight was absolutely vital in some fashion.

The oral LD50 for fructose in rats is 4g/kg bodyweight, so ignoring species differences for now and a 50kg human, they'd need 200g fructose to kill half the population.

Assuming that honey is 38.2% fructose, you'd need 524g of honey, which adjusted for density is 374mL or just over a third of a stomach's worth.

Even if you account for adaptations, the fructose processing of the bird folk will have to be over 3 times more efficient than regular humans and given that we're essentially former tree dwelling mammals who used to gorge ourselves on fruit at the end of every summer, our fructose processing rate isn't too shabby.

I'm very much agreeing with Haigus in that these bird folk primarily use passive flight with only minimal active flight activities; regardless I think we're just going to have to disagree on this subject - we've presented both sides of the argument, so rs2excelsior has a choice of options (it could be even both, with a highly physically active warrior caste preferring a high honey diet and the more sedentary castes preferring meat and fat).

[Carl]

The oral LD50 for fructose in rats is 4g/kg bodyweight, so ignoring species differences for now and a 50kg human, they'd need 200g fructose to kill half the population.

Assuming that honey is 38.2% fructose, you'd need 524g of honey, which adjusted for density is 374mL or just over a third of a stomach's worth.

Even if you account for adaptations, the fructose processing of the bird folk will have to be over 3 times more efficient than regular humans and given that we're essentially former tree dwelling mammals who used to gorge ourselves on fruit at the end of every summer, our fructose processing rate isn't too shabby.

I'm very much agreeing with Haigus in that these bird folk primarily use passive flight with only minimal active flight activities; regardless I think we're just going to have to disagree on this subject - we've presented both sides of the argument, so rs2excelsior has a choice of options (it could be even both, with a highly physically active warrior caste preferring a high honey diet and the more sedentary castes preferring meat and fat).

I agree we've more or less reached the limit but you got me curious with the stuff on fructose and the irony of what i found is doubly worth sharing. According to the wiki page for fructose one of the most frusose dense (in terms of fraction of total sugars and carbs), fruits is the fig. Something several species of birds will happily subsist entirely on whilst they're abundant. I figured there was probably something in nature that subsisted on a high fructose diet, but thats a little too perfect .

Anyway nice having the discussion, i love getting into little details like this.


Probably going to have a question of my own in the near future. Off to do some research though see if a quick search turns anything up.

[Mr Beer]

I think it's reasonable that bird-people can cope with a diet that would be terrible for a human because adaptation is a thing. A plausible bird-people would be consuming a lot of calorie-dense food, that's the important take out.

Re. the cooking thing, I read a book where the author claimed cooking was likely core to humanity, that we had been cooking for a very long time, as in millions of years.

He went into a lot of detail about the physiological differences between humans and chimps and how we are adapted to cooked food and they are adapted to raw food e.g. mouth size, jaw strength, size of intestines etc.

He also spent time talking about how raw food diets are basically terrible for humans. Allegedly women who go on a raw food diet tend to stop menstruating. That's with access to modern supermarkets and an effectively unlimited food budget. They're not having to go and physically hunt down food.

[Mike_G]

Cooked food is a lot easier to digest, and cooking makes a lot of food that would be inedible edible.

So it probably did have a huge effect on our evolution and allowed us to get a lot more benefit from the food we could get our hands on.

[Galloglaich]

The honey bee thing has some kind of historical context;

Slavs in the period roughly 8th-13th Century (and maybe later) used to incorporate bee hives in the defensive rings (usually made of a combination of stones and logs) around their villages. This served two purposes, it helped in defense and as an early-warning system, and it provided a substantial part of their industry. Honey for food and wax for candles and other stuff. Wax in particular remained a very important trade commodity in the region for centuries.

The whole thing also calls into mind honey harvesting in the Himalayas



In general on the military level it seems like you end up with a trade off between a kind of 'flying light cavalry' - phenomenally mobile but also highly vulnerable and almost incapable (more so than any cavalry) of combat in close quarters unless the target is already fleeing or almost defenseless.

If you are sticking to anything like real-world physics I imagine their huge wingspans would make them even more vulnerable and the wings would be one of the best target for ground forces. I was thinking something like bolas would be particularly dangerous for these flying creatures.

Incorporating bolas or chain shot ammunition at various levels might be a particularly effective way for experienced ground based defenders to fight off attacking bird men.

On the simplest level, either hand thrown or stick-assisted thrown bolas could possibly entangle low-flying birdmen. I assume they would have to fly low to hit anyone with a javelin. You might also be able to incorporate something like a bola into a rocket or a 'hand mortars' grenade - in the latter it would be relatively harmless to people on the ground in case of a misfire, say two or three pebbles with a very long cord connecting them which is safer than some kind of flammable or exploding shrapnel based projectile- but quite dangerous for a flying beast or bird man.

On a more prepared position, like a gun on a war-wagon, you could have stuff like chain shot, but use longer chains.



https://en.wikipedia.org/wiki/Chain-shot

This was used to destroy rigging on ships but I suspect could also be quite effective against winged creatures.


So all this sets up a kind of chess game.

Bird men would be hard-pressed to attack well prepared troops for example in forts, on warships, or traveling with war-wagons. Or carrying 'hand mortar' type grenade launchers. These kinds of targets would only really be vulnerable to high-altitude attacks like from steel darts and incendiary devices as has been discussed, but they could protect themselves from that by creating large volumes of smoke.



Less prepared but still armed targets, like cavalry armed with bows or crossbows, merchant ships armed with light cannon, and small lightly defended forts could be vulnerable.

Unprepared 'soft' targets, civilians lacking in serious military weapons - might still try to defend themselves with bolas or darts, but would be much more vulnerable to attack.

The birdmen would also be able to provide any allies with excellent C3I and should be able to often observe without themselves being seen (especially if they could use camoflage)

Presumably, ground based forces could try to launch dangerous expeditions up into mountain fastnesses to attack and harass birdmen settlements. I don't know about the physiology / physics of birdmen but apparently condors could fly as high as 15,000 feet, astoundingly, so perhaps the birdmen would have some huge mountain they lived on. Could make for an interesting expedition!

G

[Max_Killjoy]

Presumably, ground based forces could try to launch dangerous expeditions up into mountain fastnesses to attack and harass birdmen settlements. I don't know about the physiology / physics of birdmen but apparently condors could fly as high as 15,000 feet, astoundingly, so perhaps the birdmen would have some huge mountain they lived on. Could make for an interesting expedition!

There are cranes and geese that migrate over the Himalayas, and raptors that prey on them. There are anecdotal reports of bar-headed geese flying above the highest peaks.

Varying by species, birds have a remarkably more efficient respiratory system than mammals -- they're effectively pushing air in one direction through their lungs while they breath in and out, if I understand the physiology correctly, so that there are no pauses and the entire lung is refreshed continually, instead of getting stale air built up at the "bottom" of each breath that has to be pushed out.