One of the main reasons that Africa is considered the home of modern humans is that African people are more genetically diverse than non-Africans. The reason given for this is that as humans left Africa and populated the other continents, they did so in smaller groups with a subset of the original genetic diversity that was lost over time due to founder effects and bottlenecks.
I have posted on the loss of genetic diversity in America after its discovery by Europeans in 1492, due to war, exploitation, and disease. I have also posted about archaic introgression in Africa (where ancient hominns intermingled with African humans quite recently increasing their genetic diversity.
Both factors make Amerindians seem less diverse than the supposedly "original" human stock in Africa.
Below I quote a paper on the latter (archaic introgression in modern Africans) which took place AFTER people supposedly left Africa to settle elsewhere.
"Additionally, the genomes of Hadza, Sandawe, Biaka, Baka, and San people bear evidence of a small fraction of introgression from highly genetically divergent populations that no longer exist (Hammer et al., 2011; Lachance et al., 2012; Beltrame et al., 2016; Hsieh et al., 2016). The implication of these observations is that tropical and subequatorial Africa were home to multiple genetically divergent populations of hominins. Some of these populations diverged in the Early Pleistocene, and had genomes that were equally or more diverse than those of Neanderthals, Denisovans, or contemporary modern humans. Some of these populations survived and hybridized after the initial diversification of modern humans, perhaps as recently as 35,000 years ago (Hammer et al., 2011) or even into the early Holocene (Hsieh et al., 2016)
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Genetic evidence shows that equally diverse populations of archaic humans once existed in subequatorial Africa (Hammer et al., 2011; Stringer, 2011; Lachance et al., 2012), and although no fossil evidence can yet be associated with such evidence of genetic introgression, the Middle Pleistocene record of this region does speak to the presence of morphological diversity. Within this context, H. naledi provides fossil evidence of one subequatorial lineage, and we do not yet know whether it contributed to the modern human gene pool."
See: Lee R BergerJohn HawksPaul HGM DirksMarina ElliottEric M Roberts (2017) Homo naledi and Pleistocene hominin evolution in subequatorial Africa eLife 6:e24234. https://doi.org/10.7554/eLife.24234
Homo naledi is an extremely primitive-looking hominin that lived until recently. It coexisted with other more advanced hominins. They too, the paper suggests, could be the outcome of hybridization of different ancient hominins: "The mosaic anatomy of H. naledi, which includes many shared derived characters of modern humans and H. erectus, might suggest the hypothesis that H. naledi resulted from the hybridization of a more human-like population and a late-surviving australopith. This hypothesis remains untestable with the current evidence, although it seems more parsimonious to suggest that H. naledi itself survived from an early period of diversification of Homo. Morphology does not rule out the possibility that H. naledi originated in the Early Pleistocene as a result of the hybridization of different populations, and persisted long after this hybrid speciation."
Naledi lived in South Africa, and the most diverse humans also live there... coincidence?
John Hawks who was a key member in the team that discovered H. naledi has something to say about introgression in a 2017 paper, where he states that "Considering that introgression or gene flow were widespread during human origins, the ancient divergence between archaic and modern human populations that interacted with each other may be one of the strongest influences on genetic diversity in humans today." He also acknowledges introgression in Africa: "Many different genetically divergent source populations for introgression may have existed within Africa, from archaic human populations as represented by the Kabwe, Florisbad, or Iwo Eleru crania, to “near-modern” human populations that nonetheless were strongly morphologically variable (reviewed by Stringer, 2016; Bräuer, 2008), possibly to highly-divergent hominin populations such as Homo naledi (Berger et al., 2015)."
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2025by Austin Whittall ©
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