The great white pelican has one of the widest wingspans known to scientists, measuring 3.6 meters across. This wingspan is strong enough to support the lesser weight of the bird. If humans were to fly, they would require wings so large that the weight of the wings themselves would prevent flight
Although mankind has conquered the skies with airplanes, we have yet to match up to our winged animal counterparts who fly on their own. And now, scientists have determined that we never will: it is mathematically impossible for humans to fly like birds.
A bird can fly because its wingspan and the wing muscle strength are in balance with its body size. It has a lightweight skeleton with hollow bones, which puts a smaller load on its wings. A bird also has air sacs connected to its lungs, which makes it even lighter and allows for easy passage of air through its lungs during flight.
On the other hand, calculations of the ratio between human size and strength reveal that our species will never be able to take flight unaided. As an organism grows, its weight increases at a faster rate than its strength. Thus, an average adult male human would need a wingspan of at least 6.7 meters to fly. This calculation does not even take into account that these wings themselves would be too heavy to function.
There is a reason that a 6-year-old girl can do more pull-ups than her 40-year-old father — she may be weaker, but her strength-to-size ratio is still greater than her father’s ratio. In other words, humans are not too large to fly, but our strength simply cannot support our weight in flight.
Surely, humans have tried to make this work. It seems like it could work. Unfortunately, I think we are doomed to remain as ground-based animals. Well, that is unless you count powered flight or gliding. We can do both of those.
Then why not? Perhaps the simplest answer is “we are too big.” Oh, too big you say? Well, surely we aren’t too big. Maybe if we just had bigger wings, it would work. Nope. It won’t work (well, probably won’t work). This falls into a category of things called “stuff that doesn’t scale like your intuition.” Or perhaps I should say “bigger things aren’t the same as smaller things.”