The speed of evolution depends on a number of factors. I think the two most important are how fast the species can produce a new generation, and how strong the pressure causing the evolution is. Sometimes animals can evolve very quickly, if they have to, such as bacteria evolving into antibiotic resistant forms. But also sometimes animals will hardly change at all for millions of years. For example crocodiles and sharks are essentially unchanged for millions of years.
I think they the process of evolution occurs all of the time. So different versions of a gene will appear in humans still, but this will only cause a change if there is a benefit to the ability to survive and breed. At the moment I think humans will be evolving quite slowly.
Hmm, the first part of the question is hard to answer. It is hard to say who “us” is – were we already who we are 2000 years ago (probably yes); 20 000 years ago (probably yes…), 2 00 000 years ago (not sure), 2 million years ago (hmm, perhaps not). But what I can tell you is that we started off evolving into who we are from a chimp-like ancestor about 5ish million years ago. As to whether we are evolving now, we definitely are, and it looks like we are evolving faster and faster by the millennium!
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