A squat compact and robust body was necessary for the Ice Age. Because they were in the colder climates they covered their bodies which deprived them of vitamin 'D' and they turned white.
Correction: we are both human, but different species of human. We are Cro-Magnon - they were Neanderthal. The DNA is different.
We did not evolve from Neanderthal, but we may very well have intermingled with them, and produced viable off-spring, though almost all of them would have been mules (unable to reproduce).
I think the correct word is a 'singularity', and describes a fundamental change in humanity. With the ever-accelerating advances in computer technology and bio-engineering, we may yet get to see one or more 'singularities'.
An 'Artificial-Intelligence' computer similar to HAL 9000, or an engineered-human-being with no disease and an incredibly long lifespan are visible in the near future.
Just food for thought - we'll probably kill them............FRegards