1.19 migration waves and genetic diversity
Map of early human migrations according to mitochondrial population genetics. Characters represent different haplo groups. All Out-of-Africa groups descend from the African L3M group.
The early OoA-migration was around 2 mya, by H. ergaster groups. Researchers name this Early People dispersion OoA I.
The AMH dispersion of OoA II occurred in two main waves. The first, from around 120,000 years ago, is called OoA II-A. The presence of these early AMHs has been demonstrated with their fossil remains in the caves of Skhul an Qafzeh. but everything indicates that this wave has not been limited to this evidence but that other groups of this wave have migrated further to the Far East, ending around 70,000 ya in Australia.
The second, OoA II-B (65,000 ya), took place after the Toba bottleneck, and within this wave fall the 7 mitochondrial daughters of Eva, as Bryan Sykes states in his 2005 book, and began dispersing all over the world.
OoA II-A took place in a warm period when the Sahara barrier was green. So perhaps this wave left Africa along the Levant. As mentioned above, AMH hand axes are found on the Arabian Peninsula dated 125.000 years ago. Paleos have found fossil AMH remains dated 120,000 years old in the Mount Carmel caves Skhul and Qafzeh (Israël). Their stone assemblages did not differ from those made by the Neanderthals who had survived the severe cold period after the Toba catastrophe in the same caves, which during that period were abandoned by the AMHs. The paleos see the OoA II-A wave as ‘archaic AMHs’, because they do not yet show the more modern life style of the post-Toba Blombos populations in the Southern tip of Africa.
We can follow the migrations by looking at archaeological remains. We can also reconstruct them by looking at the dispersal of different types of musical traditions[1]. But the most clearly we can follow the migrations by looking at the tree of mitochondrial genetics, as in the map above.
Genetic diversity in present-day Africa is extremely high (even between closely related groups or groups living in each other’s’ vicinity) and much higher than diversity in human populations outside Africa.
This diversity suggests a recent African origin for modern humans, because in the rest of the world the genetic diversity is much smaller.
Tishkoff[2] also suggests that the group which migrated out of Africa came from northern East Africa. “The diversity of groups in Ethiopia and Somalia is intermediate between that of the rest of Africa and the rest of the world,” according to Tishkoff, “Perhaps this group was isolated from the rest of the African continent before they migrated into the Middle East and Europe.” As said, this first OoAII-A group doesn’t show the life style of the southern AMHs of Blombos cave and other sites. So this archaic group may have been driven northwards along the Nile by the population pressure of more modern AMHs from the south. Because their first appearance outside Africa is on the Arabic Peninsula, near the Strait of Hormuz (Jebel Faya, 128,000 years ago) and they appear in the Levant 8000 years later, it is also possible that they left Africa by crossing the Strait of Bab el Mandab. Or should we suppose two emigration groups of archaic AMHs? Because their stone technology is a little different.
Most of the ‘archaic AMHs’ (OoA II-A) moved ‘beachcombing’ to the East. In this relatively warm period, lush vegetation on the Arabic Peninsula made it habitable for grazing animals and their human predators. Recently, African-looking hand axes have been found in Jebel Faya (UAE)[3] . From there, migration to India may have taken place, where we find them “spearing dinner and filleting meat” 76,000 years ago in Jwalapuram.[4] At the moment of the Toba catastrophe, most of them had already passed that area, beachcombing farther eastward. Their descendants populated Sundaland and eventually reached the Sahul continent (New Guinea, Australia, Tasmania).
Today we still find descendants of these early AMHs (OoA II-A) in the jungle of Malaysia: the Semang. The Malaysians name them Orang Asli, and in the Philippines they are named Negritos.
We have to admit that the most recent Ancient-DNA as published in David Reich’s book Who We Are and How We Got Here (Oxford Un.Press, 2018) is not integrated in this text.
negrito girl
