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The classic image of the angel is a winged humanoid superior to humans in power and intelligence. How do we make this biologically real?

For starters, no wings anchored to the shoulders! Finding an evolutionary justification for this is a massive headache. Besides, it's also a cliche unto itself.

My first proposal is that there are actually two major groups of angels--the "common angels", inspired by both bats and pterosaurs; and the "classic angels", inspired not by modern birds, but by the "four-winged dinosaur".

But before we differentiate the two groups, let me list my proposals on how alike they are:

  1. Tetrachromacy--all mythological humanoids have a fourth color receptor, which allows them to see colors beyond the visible spectrum.
  2. Respiration--all mythological humanoids have lungs taking up 15% of their overall body volume, rather than the typical mammalian 7%. In both angels, air sacs are added so that they can both breathe and cool down more efficiently.
  3. Circulation--all mythological humanoids have hearts so large that if they were human, they would be diagnosed with the condition called "cardiomegaly".
  4. Chest--both angels have an enlarged sternum, or "keel", equal in size proportion to a pigeon's (by itself, proportionately larger than a raptor's) for maximum takeoff strength.
  5. Legs--in proportion to length, both angels have human legs, but human legbones are thick and wide, so my proposal is to narrow them down so that they are more gibbon-like than human-like.
  6. Abdomen--the previous proposal applies to the ribcage as well, thus allowing the bulk of the musculature to be focused on the chest and arms, crucial for flight.
  7. Bones--obviously, hollow bones help reduce the body's weight without sacrificing its strength, another cruciality for flight.
  8. Brain--both angels have proportionately larger brains than ours. For example, the common angels have a cranial area averaging 1720 cubic centimeters. In both angels, the flocculus, a region that integrates signals from joints, muscles, skin and balance organs, makes up 2% of the total brain mass. (I was originally going to propose raising the percentage to 7.5%, so it can be more pterosaur-like, but recent science has proposed a potential relationship between flocculus size and behavior complexity.)
  9. Arms--in proportion to body size, the humerus, radius and ulna are all gibbon-length, not human-length (17% of overall body length, rather than our 11%). The hand is still human-like, though instead of nails, they'd have claws.

The differences between common and classic angels, though present, still don't hold a candle to the similarities. But propose them, I must.

The common angels still have their extra-long gibbon-arms, but if we compare their fingers to our own, we'd find that the common angel's ring fingers and pinkies have lengthened by 850%. Connecting them all the way down to their ankles are solid sheets of skin strengthened by actinofibrils, fibers spaced closely together. The wing membranes also contain a thin layer of muscle, fibrous tissue, and a unique, complex circulatory system of looping blood vessels, exactly like pterosaurs. Their whole bodies are covered not in regular mammalian fur, but pycnofibers, again like pterosaurs.

The classic angel, on the other hand, are coated in feathers. They have not the traditional two wings, but four, just like the ancient dinosaur Microraptor. They are also smaller--whereas the average male common angel is 5'2" in height, the average male classic angel is 5'0". (Females from both groups are 3/4 the male's size.)

Are any of my proposals listed above sound, or have I created some unintentional side effects to the angel bodies?

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marked as duplicate by TrEs-2b, Hohmannfan, Ranger, Green, ckersch Sep 22 '16 at 21:24

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    $\begingroup$ related worldbuilding.stackexchange.com/q/25466/19699 $\endgroup$ – Kevin Rock Sep 22 '16 at 16:10
  • $\begingroup$ Two key considerations are how fast you want them to be able to fly and how much they weigh. In a recent answer about Pegasuses, for example, I calculated that to just edge out a world-class human sprinter those horses would require wings greater than 33' in length each (not counting the weight of the wings!). I suspect you're going to have a similar issue with these creatures, though I think you can skive off advanced aeronautic principles when talking about mythical creatures anyway. $\endgroup$ – GrinningX Sep 22 '16 at 17:06
  • $\begingroup$ @GrinningX "Skive off"? $\endgroup$ – JohnWDailey Sep 22 '16 at 18:40
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    $\begingroup$ I agree that this is NOT a duplicate. If you read through the criteria this isn't an attempt to find out what would actually happen if an angel had to be real, it's about whether a specific type of creature (inspired by angel lore perhaps, but distinct itself) is feasible. $\endgroup$ – GrinningX Sep 22 '16 at 21:51
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    $\begingroup$ I don't think this is a dup. There's a good distinction between cliché angels and these avian humanoids. $\endgroup$ – B.fox Feb 12 at 20:30
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a- Skeletal Structure

You are going to need a very very very light skeleton. That's a pre-requisite. We are talking about extremely hollow bones here. At least bird-grade bones or better yet, if you can get pterosaur-grade bones. Pterosaurs were those huge flying monsters that ruled the skies in the times of dinosaurs. Their bones were extremely lightweight. A huge pterosaur (3 times the size of a human) would have bones completely hollow and no more than 1 mm thick. Yeah, now we are talking.

b- Wings

If you examine any flying creature you will find out that their width is greater than their length. That is, you open up their wings, the wingspan will be greater than their length. So a human with 6 ft height would have a wingspan of at least 11 feet when the wings are fully open. Of course the human will fold the wings and keep them on their back just like birds, when not in use.

The next issue is the wing SURFACE AREA. Are you going to opt for membranous wings (like pterosaurs or bats), crustacean wings (membranous, but different type, ones you see on insects) or feather wings (self explanatory, all bird wings are these types)? I think crustacean wings are not an option as they cannot take high air pressure and would tear open quickly.

Bird feathers are very strong and offer the best air-thrust method, but they are also heavy. Yes! For the scale of human flight, bird feather WOULD be heavy. If you want to use bird feathers for human flight, the shoulder muscles would have to be really really powerful. In case of membranous wings (bat/pterosaur grade), these are relatively light and you can make do with lesser shoulder muscles.

c- Flight Muscle Attachment Points

If you want your flying humans to have wings AND arms separately, then things could get slightly complicated. You are going to have to form muscle attachment points for the wing muscles. These have to have an anchor point on the chest region, like all birds and pterosaurs. So your flying humans are going to have really really stocky and strong chests.

d- Flight Posture

How are your flying humans going to look like, in mid-flight? Are they going to fly in horizontal body posture (like most birds) or vertical posture (the way they stand, looking somewhat like a hovering humming bird)? I cannot answer this myself as it involves a lot of complex aerodynamics, but I think a horizontal flight posture is more likely.

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  • $\begingroup$ No, I do NOT want the arms and wings separately! That's diving into cliche territory. And it looks like you haven't read the whole thing. $\endgroup$ – JohnWDailey Sep 22 '16 at 18:22
  • $\begingroup$ @JohnWDailey the same logic applies here. $\endgroup$ – TrEs-2b Sep 22 '16 at 18:36
  • $\begingroup$ So like I said, it looks like you haven't read the whole thing. I've already mentioned the hollow bones and the keel. $\endgroup$ – JohnWDailey Sep 22 '16 at 18:38
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    $\begingroup$ @JohnWDailey then you've answered you question in your answer. $\endgroup$ – TrEs-2b Sep 22 '16 at 18:40
  • $\begingroup$ @TrEs-2b I believe this is a reality-check type question. While the author seems to have a general idea of how to implement what they want they aren't sure that it would actually work $\endgroup$ – Annonymus Sep 22 '16 at 19:56

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