This is my personal observation that keeps me skeptical of evolution. Why did the creatures created by the stages of evolution between one species and the next die out. Simple and extremely complex organisms coexist to gether. So why couldn't a less developed human survive? It must have survived long enough to evolve into us.
If I evolved the ability to breath under water that would not lead to all other humans dying out.
To me species look complete and not on the verge of any kind of speciation. Plus it must have taken millions of very gradual mutations to create us. So we can't have gone from monkey to human overnight which makes it essential that intermediates hang around for a long time.