Why did birds not evolve to have propellers instead of flapping wings?

Why did birds not evolve to have propellers instead of flapping wings?
Propellers are much more efficient than flapping. Are birds just too dumb for propellers?

>Propellers are much more efficient than flapping
>birds just too dumb

OK smarty pants. Please show us your designs for an organic based propeller that's more efficient than flapping.

Pic related my man. We move the brain back into the body to allow for the v6 muscle powered engine.

Red is the blood.
Pink the muscle.
Yellow the brain/neurons

The propellers can be made from bone or toenail.

Propellers don't glide at all. Bird's design allows it to glide and conserve energy while there's wind and flap wings otherwise.

Because evolution doesn't get to just jump straight to building any useful thing possible. It's and extremely gradual step by step process. A human engineer can go straight to working on a propeller but evolution works by first having a small new detail of a trait emerge and then having some more detail emerge etc. with every single step working well enough that the creatures with those intermediate traits continue to thrive and reproduce.

Evolution isn't even real.

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Prove that propellers are more efficient than flapping. It's difficult to fold propellers in when landed or change flight characteristics of propellers

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Why did you not evolve to have gray matter in your head instead of mashed potatoes?

Shit you're right

Why have people not evolved wheels, pedals and a chain? Cycling is much more efficient than walking.

To my knowledge, there is only one example of free spinning wheels or gears in an animal, and it's in the stomach of some weird snail. It's just not very easy to evolve.

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>Propellers are much more efficient than flapping.
They're not though. We use them to fly because it's much easier to engineer a propeller than it is to make an ornithopter that works. There are also scaling problems.

I think it's a muscle. And the flagellum of bacteria.

does the propellerbird have fixed or variable wing geometry? This is important. It may be necessary for it to strafe soft targets while flying at low altitude at low speed

Lets say this would be feasible. Natural Selection still doesn't produce ultra efficient biological machines. Only the minimum necessary in order to survive and replicate. It builds off existing structures that are anatomically similar in all animals. For example: The bones that form the human hand are the same bones that produce a whale's fins and a bat's wings. For the most part, we all start out pretty similar.

this

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Because most animals cannot evolve away from 4 limbs, that's why lots of animals use their tales to grasp things.

Thanks Schubin

I can't think of any animals that grasp things by their tails.

Because evolution is driven my random mutations being passed on when organisms reproduce.

Niggers

Opossum and monkeys. Things with prehensile tails.