1. Why are all other Homo's in the Genus (except us) extinct?
Because they either were out competed or were unable to adapt to the environment..
2. As we continue to evolve will there eventually be another speciation event where a group of humans become too genetically incompatible with another? Or since we are so great in number and widespread is this no longer possible?
Although I'm sure we can debate this. I honestly don't see humans evolving all that much over time. We adapt or environments to us instead of falling victim to it like other species. The only force I see still at work is sexual selection and even then most humans still will have a chance to reproduce...
3. Regarding human origin and ancestry specifically the relation of Humans and Neanderthals: what common ancestor do we share with them? And how long ago was the split?
Somewhere around 600'000-500'000 years ago and I've read it was Homo rhodesiensis
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