Greater Neanderthal admixture is the likely explanation for why humans who left Africa advanced more rapidly than those who remained; climate probably less so, given that those who migrated across the Bering Strait and became the "indigenous" peoples of the Americas advanced at least as far as the early Egyptians in Central and South America at latitudes closer to Africa, whereas in North America in climates more similar to Europe they largely remained hunter-gatherers. The "climate theory" of civilization development is mostly just another cope to avoid accepting the reality of sub-Saharans.