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Originally Posted by sohvan
I don't think humanity has stopped evolving, but rather the genetic evolution has slowed down considerably. I think the ideas left behind by invidual people have had a far greater effect for a long time, than contributions to the gene pool.
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And what on Earth would account for evolution slowing?
Evolution is very slow but the mechanisms for genetic changes are relatively constant over time. When populations become isolated, when there are significant selection pressures such as a global catastrophe, (since humans populate all continents), then new species can emerge.
Our gene pool was reduced to a few thousand members about 70,000 years ago but no truly new race or species evolved. It left us with less genetic diversity. Chimpanzees have much greater genetic diversity than humans. We have room for expanding our genetic diversity without significantly changing our human characteristics.
Bottom line, evolutionary changes march continually on. Other factors determine when we will see a considerably different species evolve.
As to the increasing size, there is more evidence that is the result of nutrition than genes but there is some genetic basis for taller and shorter body types. Zulus vs Pygmys tribes' size would be genetic diversity but increased size of Americans from the 1700s to the 1900s would be more from nutritional effects.