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I have an idea for a story where human live on world with low gravity and a dense atmosphere. These humans have developed artificial wings that are attached to their arms so they can fly. Since the shoulders of birds and bats have changed to facilitate the motion needed for flight, I was wondering if human shoulders would have the range of motion needed for a flight stroke.

If no, then could the human shoulder change its shape through bone remodeling in response to the stress of flight to make flying easier?

Edit: The gravity is 0.31g and the atmospheric density is 5.29 kg/m3

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  • $\begingroup$ How low gravity and how dense atmosphere you imagine on your planet? $\endgroup$ – Artemijs Danilovs Nov 23 '18 at 23:30
  • $\begingroup$ I was thinking that the motion could be mainly amplified by motions of the elbow thru wrist, relative to the upper arm. iow, not relying upon muscle power, but lower arms as actuators to mechanical wings. this could theoretically work even on earth. $\endgroup$ – theRiley Nov 24 '18 at 0:25
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They certainly can given the right conditions.

Humans might be able to fly on Titan—if they use large enough wings https://io9.gizmodo.com/humans-might-be-able-to-fly-on-titan-if-they-use-large-1536169825

If the density of the atmosphere is the same as the density of their bodies then they are effectively swimming. They can do the breast stroke. Swimmers have pretty much neutral buoyancy so gravity doesn't come into it much. With altitude the atmosphere becomes less dense so achieving altitude would become increasingly difficult.

Look at the shoulder range of motion that swimmers have. The butterfly stroke and backstroke prove that mobility is very extensive.

What if the density of the atmosphere is less than that of the flyers? In that case there will be a limit beyond which humanoids cannot go. They can wear increasingly large wings but eventually their muscles and skeleton won't be able to cope.

Can humans fly like birds? https://engineering.mit.edu/engage/ask-an-engineer/can-humans-fly-like-birds/

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Very interesting question. The shoulders of homo sapiens have evolved to throw projectiles with great power and precision. That's why chimpanzees and apes can't throw a baseball very well. However, the shoulder of the homo sapiens are at greater risk of injury and dislocation because of that increased range of motion. Weight lifters and athletes often injure their shoulders during routine exercises.

https://www.bbc.com/news/science-environment-23061016

Flight is quite complicated, however. A bird's wings don't just flap back and forth. There are many angles, bends, and twists to navigate around tree branches and escape predators. How would a pair of artificial wings manage all those twists? A human's torso and legs are also very heavy, so flying would take as much strength as doing fifty pull-ups per minute using the latissimus muscles. Flying in a denser fluid (i.e. water) definitely helps, but at some point won't the human's lungs also need to evolve to breathe that heavy fluid?

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