[mlc9852]

I've always wondered why we can't fly. It would be a major benefit I think. Why haven't we been able to adapt to flight?

[CarolinaGuitarman]

"I've always wondered why we can't fly. It would be a major benefit I think. Why haven't we been able to adapt to flight?"

Who says we didn't?

[Thatcherite]

Flight comes at an extremely high cost, which has to be paid for out of other capabilities that the species could have had. Numerous adaptions are required. Ultra-light skeleton (if you ever hold a large bird of prey on your arm you will be astounded at how little it weighs). Massive musculature and metabolic capacity for the purposes of flight. Creatures of our size couldn't conceivably evolve flight. The power requirements and stress loads are way too great.

Its no coincidence that oceanic islands often have flightless bird species living on them. These arrived there originally as a single normal flying bird pregnant female (perhaps in a storm), millions of years ago, and over time the descendants lost the ability to fly because in the ecological niche they find themselves flight isn't that big an advantage. Usually such islands won't have predators, and the newly arrived bird finds itself at the top of the food chain. The ability to fly is no longer important and the high cost of maintaining it is greater than the reproductive benefit. Through the generations the ability is lost as less good fliers that are born outbreed better flier siblings because the less good fliers are better adapted to the island environment in other ways. That is why oceanic islands often have a unique species of flightless bird, and of course no two such islands share the same species, because the flightlessness evolved after the first pregnant female flew there.

[b_sharp]

"I've always wondered why we can't fly. It would be a major benefit I think. Why haven't we been able to adapt to flight?

Why do you believe that just because something may be a good idea that some organism should have evolved that way? Evolution has no direction, no intent. Its all contingent on what it starts with and what mutations just happen to occur.

Mutation (variation) happens first then the environment decides if it will allow it. Talk about complex systems. The interaction between the organism's parts and thingees and the environment is highly complex.