Our planet was very different 100 ka ago, and if we could survey that time, we would be astounded by the human diversity across its surface. To enumerate what little we know with certainty, there were at a minimum: modern humans, Neanderthals, at least 3-4 varieties of Denisovans, and 2 pygmy Homo populations in Southeast Asia. Likely there were still remnant Homo erectus in Southeast Asia as well, and other diverged lineages within Africa, and a new Homo in Nesher Ramla, Israel, in the Middle East with affinities to Neanderthals.

2023-02-04: More evidence of a much more distributed situation

“Cognitive revolutions”—such as the widespread shift some 300 ka BP from clunky, handheld stone tools to more refined blades and projectile points—were probably instances of different populations with distinctive cultural and biological features coming together and recombining their genes and ideas.

This mosaic evolution would explain certain seemingly unexplainable findings. For example, researchers found human fossils in the Democratic Republic of Congo that dated to 22 ka BP but physically resembled people living 300 ka BP. In Senegal, scientists uncovered 12 ka BP stone toolkits that could easily be transplanted to a situation 100 ka BP.

These finds probably resulted from periods of isolation where different populations in different parts of the continent each developed distinctive cultural and physical adaptations to their local environments. At the same time, instances of connectivity allowed different populations to acquire beneficial traits, behaviors, and technologies from one another, becoming better adapted and more flexible.

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