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After almost forty years of scientific consensus could we be seeing the end of the ‘Recent Out of Africa Theory’ of human origins. The fundamental claim of this theory is that the ancestors of modern Eurasians and Americans lived in Africa 70,000 years ago, before gradually migrating into the world beyond close to 60,000 years ago. Several new studies have left this model looking shaky at best if not perhaps completely disproven.
In July 2017, archaeological discoveries made at the Madjedbebe rock shelter site in northern Australia forced the scientific community to recognise that humans had reached Australia at least 65,000 – 80,000 years ago. The new finds ended decades of belief in a maximum 50,000-year long occupation of the continent. The results of the archaeological investigation appeared in the scientific journal Nature under the title ‘Human occupation of northern Australia by 65,000 years ago’.
The popular consensus theory of ‘recent out of Africa’ states that African migrants began their journey towards Australia between 70,000 – 60,000 years ago, with genetic data favouring the more recent end of this scale. These early explorers apparently reached Southeast Asia and then built the world’s first boats, sailing off into the great unknown to reach Australia 50,000 years ago. With the announcement of a 65,000-year-old Aboriginal site, this popular narrative began to look completely unbelievable.
“People got here much earlier than we thought, which means, of course, they must also have left Africa much earlier to have travelled on their long journey through Asia and south-east Asia to Australia,” said the lead author, Associate Prof Chris Clarkson, from the University of Queensland.
It is certainly difficult to conceive of a way in which the presence of humans in Australia 65,000 years ago, can be explained by a migration moving slowly eastwards out of Africa around 70,000 to 60,000 years ago and passing through the vastness of Eurasia. We then must ignore the peculiar fact that these migrants did not settle anywhere along the route and left no evidence of their journey. Why do these pioneers reach the coast of Southeast Asia and then build boats so that they can sail onwards, heading toward a continent they can’t even see on the horizon?
A growing number of scientists have claimed that we can easily explain the early presence of modern humans in Australia by simply moving the start of their migration back a few thousand years, perhaps to 80,000 years ago or earlier. The problem with this convenient revisionary tactic is that there is no evidence in support of it. Multiple genomic studies have indicated that the ancestors of modern Eurasians diverged from their source population between 60,000 and 50,000 years ago, with a preference for 55,000. There is also the troublesome matter of how this the beginnings of this migration were linked to Africa in the first place, analysis of contemporary modern African DNA.
Analysis of modern African DNA reveals that ancestral Eurasian haplogroups, mitochondrial haplogroups M and N and Y-chromosomal haplogroup CF, seem to represent mutations of mtDNA HgL3 and Y-chromosomal HgCT, haplogroups associated with African ancestors living 70,000 years ago. The problem with using this recent DNA data to place the ancestors of all living humans in Africa is that it assumes the first people carrying the identified mutations were themselves on that continent. To confirm the stated assumption requires DNA from humans who definitively lived in Africa 70,000 years ago, sounds simple enough?
The problem is that the oldest sample of African DNA ever recovered is a mere 8100 years old. The lack of sufficiently old African genetic material means we can’t currently use DNA alone to geographically place the earliest ancestors of modern Africans. Let us take a leap of faith and accept the belief that the ancestors of today’s Africans lived in Africa 70,000 years ago, we still have no evidence that the haplogroups at the base of the Eurasian population were associated with these populations significantly earlier than 70,000 years ago. Moving the out of Africa migration dates backwards takes an already weak model into the realms of outright scientific fraud.
Some scientists are beginning to question whether the basal haplogroups might not perhaps relate to migrations into Africa rather than originating there. Researchers at the University of La Laguna have recently suggested that haplogroup L3 entered Africa from Asia, their paper’s title is self-explanatory enough, ‘Carriers of mitochondrial DNA macrohaplogroup L3 basic lineages migrated back to Africa from Asia around 70,000 years ago’. Though the authors of this paper still posit a possible earlier African origin for these Asian migrants, they highlight another glaring anomaly within their data:
“The southern route hypothesis proposes that the Eurasian branches (M and N) of the macrohaplogroup L3 differentiated in or near the African continent and rapidly spread across the Asian peninsulas to reach Australia and Melanesia. Under this assumption, it is expected that, in general, coalescence ages of haplogroups should decrease from Africa to Australia. However, we have demonstrated that this is not the case. Just on the contrary, the oldest M and N haplogroups are detected in southern China and Australasia instead of India, and associations between longitudinal geographic distances and relative ages of M and N haplogroups run, against to expectation, westwards with younger haplogroup ages going to Africa.”
With confirmation that humans were already living in Australasia 65,000 years ago, and that these people carried the oldest variants of the haplogroups considered ancestral for all modern Eurasians, we can begin to redraw the migration map. We know that sometime between 60,000 to 50,000 years ago, people carrying the Eurasian ancestral lineages began to move through Asia, heading westwards. These colonists moved gradually towards Europe and Africa, reaching those regions around 45,000 years ago. Logic places the source of these migrants in Australasia; no other interpretation fits the evidence so perfectly.
Once we abandon the current reliance upon DNA samples taken from contemporary Africans and instead put the focus on archaeology, palaeontology, paleoclimate modelling and archaeogenetic data, the ‘recent out of Africa theory’ looks incredibly weak, a better word might be ‘silly’. Could we soon see a far more harmonious consensus model, centred on the entirely reasonable ‘recent out of Australasia’ model?