Why can't humans fly?

If you go to ask people why can't humans fly most of them would give you the answer "because humans don't have the wings". This is the right answer but on the other hand, answer that needs much more explanation.

The life on our planet started in the water, and evolution took many million years before first creatures developed wings, and started their conquest of the sky. Evolution didn't find necessary to give us the flying ability, and instead gave us dominant intelligence, which more than compensates our physical weakness compared to many animals.

However, flying is not only about having the wings. If you look at the birds you can see that wings are only part of their flying mechanism, together with light frame of their body and light bones. Air sacs inside their bodies also play vital role because they make birds lighter which enables smoother motion through air. The shape of their body is also important because it helps reduce the air resistance when flying, and their muscles are extremely powerful compared to their body.

If humans were about to fly they would need extremely large wings because our bodies are heavy, and unlike birds we also do not have air sacs to make our body lighter. Some people would likely say we could be installing some sort of artificial wings but that wouldn't work either because our muscles are not strong enough to support the wings.

Evolution had other plans with us, and thus we haven't received the gift of flying. This however could still change in far far future because if evolution feels the need for change we could even end up with wings, or some other parts needed to conquer the air in far far future.

In the meantime we need to stick with our technology to do the flying instead of us. That's not bad either.