2. The study
3. Other info
I recently came across a study that neatly summarizes the arguments and evidence for the single and multiple dispersal Out of Africa models: Human Dispersal Out of Africa: A Lasting Debate (2015) by López et al. It’s seven years old, so some of the information might be outdated, but I haven’t been able to find a more recent overview.
In my opinion, the theory that all non-African humans descend from a single dispersal out of Africa is pretty spurious. It doesn’t align with the archaeological or genetic record but, by pure coincidence, it aligns perfectly with the nefarious political agendas of globalist elites — one humanity, one world, etc.
It seems likely that humanity had already experienced some degree of racial divergence within the African continent, before any Out of Africa expansions took place. This theory is supported by living evidence in the form of the South African KhoiSan, who diverged from other humans tens or possibly hundreds of thousands of years before the first Out of Africa expansion. I think the Out of Africa expansion took place in multiple major waves that were separated by thousands of years and involved various groups of phenotypically distinct humans. I could be totally wrong but this seems like the most logical theory to me.
2. The study
Quoting the section covering the multi-dispersal model below the line.
Lahr and Foley were the first to propose that AMH populated the world via multiple rather than a single wave of expansion from a morphologically variable population in Africa.
Under their multiple dispersals model, there was an initial dispersal between 50 and 100 kya through South Arabia to Southeast Asia (the Southern route) and a second migration following the Northern route, through the Levant, that led to the colonization of the rest of Eurasia between 40 and 50 kya. They suggested that each of these dispersals was different in terms of the associated artifacts, with the first migration into the Arabian Peninsula affiliated with Middle Paleolithic stone tools and the later expansion through the Levantine corridor into Europe consistent with the appearance of upper Paleolithic tools.
Later work by Field and Lahr used a geographical information system-based model, incorporating climatic data from 74 to 59 kya, to show that both a Northern and a Southern route out of Africa would have been possible given environmental barriers.
More recently, McEvoy et al tested the multiple dispersals hypothesis by applying a LD-based approach to ∼200,000 SNPs in 17 global populations.
By testing divergence times in West and East Eurasian populations simultaneously, they found evidence for a more complex OoA scenario than that suggested by a single dispersal model. Namely, they demonstrated a significant difference in estimates of African/European and African/East Asian divergence times […] may indicate that Europe and East Asia were occupied by separate AMH dispersals.
The split time for European and East African populations (57–76 kya) was again estimated to be somewhat more recent than that for East Asia and Africa (73–88 kya), and significantly more recent than that between Australo-Melanesians and Africa (87–119 kya) even after accounting for Denisovan introgression into the ancestors of Australo-Melanesians. According to the authors, this is again inconsistent with a single wave dispersal and suggests that Australo-Melanesian populations retain signals of an ancient divergence from Africa
Reyes-Centeno et al […] used morphological data from Holocene human cranial samples found in Asia, in conjunction with genetic data, to evaluate models of modern human dispersals out of Africa. They concluded that a single dispersal model was likely too simplistic and, as with other studies, found that modern humans first went south upon leaving African and only later took the Northern route in a second expansion wave. Recently published work providing evidence for modern human introgression into the ancestors of East Asian Neanderthals 100 kya also gives support for the multiple dispersals hypothesis.
it has been suggested that some isolated Southeast Asian/Oceania populations, such as Papuans and Andamanese and Malaysian Negritos, represent relic populations of a first wave OoA. Some of this evidence is in light of autosomal DNA studies that have indicated Southeast Asia was settled by multiple waves of peoples, the first most related ancestrally to modern day groups such as the Onge and the second more closely related ancestrally to modern day East Asians.
Genetic evidence for an early Southern exit was presented by Rasmussen et al who analyzed a lock of hair from a 100-year-old Australian Aborigine. Applying D statistics to segregating sites in the genomes of modern Africans, Europeans, and Asians, they provided evidence for an early branching of Australian Aborigines 75–62 kya. These results suggest that the ancestors of Australian Aborigines are some of the best modern day representatives of a possible early human dispersal into East Asia
3. Other info
I don’t have much to add to the information above, but I did find one 2021 study by the Max Planck Institute & Co. that describes Papuans as descending from a South Eurasian (aka Australo-Melanesian) population that had already diverged from both Caucasians and East Asians:
“it is reasonable to describe Papuans as either an almost even mixture between East Asians and a [South Eurasian] lineage basal to West and East Asians […] or as a sister lineage of East Asians”
The South Eurasian lineage being “basal to West and East Asians” means that it diverged from the main “Eurasian” branch of humanity before Caucasians and East Asians did, not that it is directly ancestral to Caucasians and East Asians. Usually, geneticists claim that South Eurasians (i.e. Oceanians, South Indians, and Negritos) and East Asians descend from the same “Eastern Non-African” lineage as part of a singular Out of Africa expansion which also gave rise to the Caucasian lineage. This Eastern Non-African lineage supposedly diverged from Caucasians sometime before arriving in South Asia, and then diverged into Oceanians, South Indians, and East Asians, somewhere within South Asia. The East Asians migrated north along the Himalayas, the Oceanians island hopped south to Insular Southeast Asia, and the South Asians stayed in South Asia. I’ve always been skeptical of this claim. It might be accurate, but I prefer the Two Layer Hypothesis, which states that distinct East Asian and South Eurasian lineages migrated seperately into South, East, and Southeast Asia at different dates, and then merged over time.
I’ll edit this article if I find anything else to add but, in conclusion, we just need more samples. Too many gaps in the genetic record, too many assumptions, and too much guesswork.