This is a slight detour I guess, but I am struck by the continued discovery of earlier human species. The latest is a new species of human from the Phillipines. In the case of both the Neanderthals and Denisovans, our own species was able to interbreed with them. All Europeans, for instance, have some Neanderthal ancestry. Many inhabitants of Asia and Oceania have Denisovans ancestry. The gene for high elevation tolerance among Tibetans, for instance, stems from the Denisovans.
This recent New York Times piece briefly summarizes the discovery of the various fossils that are filling out our understanding of the human tree:
https://www.nytimes.com/2019/04/10/science/hominins-human-evolution.html
Meet Homo luzonensis, who inhabited Earth at the same time as Homo sapiens, Neanderthals, Denisovans, and Homo floresiensis( the so-called Hobbits):
https://www.scientificamerican.com/...-surprising-new-species-to-human-family-tree/
And the Denisovans were more diverse then previously thought:
https://www.smithsonianmag.com/smar...re-more-diverse-previously-thought-180971952/
And it would seem important to keep this in mind:
"The word “species” here is used tentatively. The
exact number of human species — and what counts as a species — is up for debate.
Jeremy DeSilva, Ph.D., an anthropologist unaffiliated with this new study, tells
Inverse he refers to them all as different populations of humans, rather as different species or subspecies because “it appears that both Neanderthals and Denisovans had split from the human lineage and from one another before being reabsorbed to various degrees back into the gene pool.”:
https://www.inverse.com/amp/article/54792-ancient-human-denisovan-lineage-split
I do wonder what issues involving racism would exist today if all these ancient humans still walked the Earth with us....