So i recently found this site and it proved useful for many unanswered science question except for one big one I want to know: What properties would allow for bird wings on humans, NOT connected to the arms but in a way six limbs. Before i receive answers about how "improbable" it is and "evolution" wouldn't allow it and my absolute favorite response to this question, "bat-like wings instead". Let me say this: I understand that having six limbs is most likely impossible, i know that because of washing and hiding and etc that bird wings are not logical. This is from a HYPOTHETICAL view point. Currently I'm trying to do the calculations myself because the concept is intriguing to me, and I came one here to see if anyone else had a similar question. Such conditions I'm, trying to figure out are as follows:

  1. Weight (Because i know our bones would need to be lighter)
  2. Height (Would we need to be taller or smaller than average size)
  3. Wingspan (Assuming the wings were attached to the back and were light boned and feathered)
  4. Speed (Theoretically how fast could one travel)
  5. Diet/Health (Would our diets need to change to match birds? Would we need to build more muscle?)

Most answers are mostly the same and although it is again most likely impossible, its still something i'd like an answer to. I'll update when I'm done calculating.

  • $\begingroup$ The real problem is still no place to put the muscles for 2 new limbs $\endgroup$
    – Andrey
    Feb 20, 2020 at 19:38
  • $\begingroup$ I do a lot of strength training. Let me tell you: Lighter bones is not the answer. Bones make up like 10% of your body weight. If you actually want to fly using your chest muscles, decreasing your weight even by 10% isn't going to do anything. With proper training, those 10% body weight are absolutely negligible: Even the best bench pressers can't fly one bit. I read this a lot here, lighter bones thing. Birds may have lighter bones, that's better efficiency. But that's nowhere near to a solution. If you truly want to build that world, do a couple of sets of chest flies and feel four yourself $\endgroup$
    – Raditz_35
    Feb 20, 2020 at 20:02
  • 1
    $\begingroup$ PS: Here is a suggestion, because I don't want to hear this lighter bones stuff here anymore: More strength which is kind of similar to saying better bio physics. Look how big those chicken breasts are compared to the rest of the bird. Now look at a bird that can actually fly. It basically says the same, but it makes sense now. $\endgroup$
    – Raditz_35
    Feb 20, 2020 at 20:07
  • $\begingroup$ I highly recomend you google "Ask Greg Weisman" who discussed several issues related to this to explain his titular creatures in the "Gargoyles" animated series. It should be pointed out that Gargoyles do not fly but merely glide. The energy issue was "solved" by the stone by day part (basically the stone skin was collecting solar energy). It's still a lot of Hollywood science, but his rule was Gargoyles are natural biological creatures and not magically empowered in anyway. $\endgroup$
    – hszmv
    Feb 20, 2020 at 20:08
  • $\begingroup$ The average human is at least four or five times heavier than the heaviest bird. The simple but sad truth is that humans are way to heavy to fly in the way that birds do. Humans can fly under their own power, but this requires highly advanced materials and engineering; and look how large the wings of a human-powered aircraft have to be! $\endgroup$
    – AlexP
    Feb 20, 2020 at 20:21


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