Quote Originally Posted by halfeye View Post
Wings are not all the same. They're all wings, and they work in air, but they're not the same. Bat wings and bird wings are different. Working in air is the convergent bit, but it doesn't make them the same.
Bat wings and bird wings are not that fundamentally different. They are both a mutation of the upper skeleton's forelimbs, adapted to flight by increasing the surface area. Bat wings evolved from a mammalian template - a membrane of skin between the body and the grotesquely elongated digits of a grasping manipulator. Bird wings evolved, possibly, from a reptilian template following the extinction event - the same membrane of skin, between the body and only one enlarged digit and the rest of the limb, covered in semi-articulate mutated scales adapted for flight.

They were two entirely different branches of the evolution tree, but with the same pressure (needing to fly) and similar things to work with (air, bilateral symmetry of skeleton, skin covering) they evolved into very similar structures.

We don't at all know if some of that's true, and other bits clearly aren't. There could have been reptiles with complete thermoregulation, or mammaries. Even if you ended up with mammals, people could just as easily evolve from baboons as from chimps.
And that would have been entirely fine. Baboons are still arboreal and omnivorous, they still have bilateral symmetry, sexual dimorphism, grasping appendages, vocal capacity, social structures, etc. For the purpose of this experiment it would not have mattered what exact species the "humans" ended up being.

There are plenty of alternate possible intelligent lifeforms among the mammals, or among non-vertebrates. Coconut crabs have lungs, give them a quarter of a billion years and they might become people.
They probably won't, not without being pressured to do so. Life tends to reach an equilibrium with its pressures and stay there. And even if, say, coconut crabs could evolve into a society, surely dolphins would have beaten them there. It's not about what species could become intelligent, it's about what species is the first to do so. In an Earthlike environment, with an oxygen atmosphere, sunlight, and a variety of tall and short plants and varied other animals, an omnivorous, endoskeletal, arboreal creature capable of tool use, is likely going to succeed the fastest, simply because it can make use of all kinds of foods, can move around freely to locate food sources/shelter, and once tool use begins the evolutionary pressure of the remaining surrounding threats drives it to come up with better tools to compensate for what remaining weaknesses it has, thus improving its intelligence further and faster.


Humans are a random accident, it's lucky for us, but the odds of that particular accident recurring elsewhere are quadrillions to one agains.
Humans as we know them exactly, are an accident. Humanoids in general, are just the result of a particular kind of environment and a few lucky rocks.