Yes. I think six billion years is a short time for every species ever to have existed to have evolved blindly.
How much time do you think would be needed,and how did you decide that?
Incidentally, the time that evolution has had is much less than 6 billion years. The earth is 4.6 billion years old, it had to cool, form a crust, and accumulate oceans before abiogenesis could begin, it had to endure a period of heavy bombardment that may have reset the clock multiple times, and then see replicators evolve from non-living chemicals before evolution could begin. That may have begun 3.5 billion years ago.
Then there was a huge delay before eukaryotic cells arose, and another before multi-cellular life arose. That probably takes us to 600 million years ago, meaning that all life big enough to see with the unaided eye likely evolved over the last 600 million years.
OK. Sooner or later there should be a branching off. A new species from this human species. When if ever do you think that will happen? It sure would prove evolution. Wouldn't it?
Evolution is already proven. It is observed. And the theory explaining it unassailable in its core tenets.
Man will probably have to wait until he colonizes space to see evolutionary branching. New habitats -that's the ticked. Different gravity, different radiation level, different activity levels, different diets will all contribute. And if they encounter life - simple life, no doubt - they may have to co-evolve in different ways according to what they have to contend with.
Separating populations has that effect.
Here on earth, I expect people to become more homogeneous as the races intermingle and everybody ends up light brown with more similar hair, eyes, height, etc.
Also, cultural evolution and artificial selection will play a bigger part in the changes humanity experiences than Darwinian (undirected biological) evolution. More myopic and diabetic people, for example, will survive, more otherwise infertile people will reproduce, more people with oncogenic genes will survive to pass them on, etc..
Someone thinks that the human species appeared two million years ago. No new species in two million years. Isn't that slow?
That depends what you mean by "human." If you mean any species of the genus Homo, then yes, Homo habilis is thought to have appeared about 2.5-2.7 million years ago.
If you mean Homo sapiens, then no. He has been around less than a tenth of that time.