It appears that the ancient concept of the ‘cradle of humanity’ is deeply diversified today, as researchers locate very ancient hominid remains in different parts of Europe, Asia and Africa.
Now, new research confirms the classic evidence we had of Africa as the cradle of all human beings. Specifically, it reveals the exact location of the first anatomically modern humans , and it has done so in a very innovative way: combining DNA data with a comprehensive climate study.
Scientists had already dated the appearance of the first Homo sapiens sapiens : in Africa about 200,000 years ago. What they weren’t sure of was the exact location. We now know that the first modern humans came from the Makgadikgadi-Okavango paleo-wetland in southern Africa, now located south of the Zambezi River in northern Botswana.
This exciting new data has been contributed by an international study led by the Garvan Institute for Medical Research in Australia, which has analyzed the chronological, ethnolinguistic and geographical frequency distribution of more than 1,000 mitogenomes (complete mitochondrial DNA codes) of current people of South Africa.
Mitochondrial DNA: a time capsule
Southern Africa is home to contemporary populations that represent the earliest branch of human genetic phylogeny. Mitochondrial DNA acts as a ‘time capsule’ of our ancestral mothers, so scientists were able to compare samples collected from current settlers with those of these ancient humans, the so-called L0 lineage.
As Vanessa Hayes, one of the lead authors, explains: “Comparing the complete DNA code, or mitogenome, of different individuals provides information on how closely this relationship was.” Finally, the results showed the geographic isolation of descendants south of the Zambezi river in Africa.
By establishing mitogenomic timelines, frequencies and dispersions, the study concluded that the lineage arose within the residual Makgadikgadi – Okavango paleo-wetland of southern Africa.
Specifically, the genetic divergence points to a 70,000-year existence of the lineage before a dispersal out of the northeast-southwest home. That is, the first anatomically modern humans ( Homo sapiens sapiens ) were settled there during that entire period of time, before their dispersal.
The key site locations that were used for comparison are highlighted in red. / Nature ( 2019 )
The climate study revealed the migratory movements of the first humans
Not only the study of DNA has allowed us to obtain the location of the first modern humans, but it has also provided us with data on how long these groups of individuals populated the region, and even what climatic events led to their departure, and where. The first migrations of people that appear to have been driven by regional climate changes.
The ongoing study showed evidence of significant genetic divergence in the earliest maternal sub-lineages of modern humans, meaning that our ancestors migrated from the homeland between 130,000 and 110,000 years ago.
This region of southern Africa once had the largest lake system in Africa, the ancient Makgadikgadi Lake, an ideal ecosystem for human life to flourish. But, over the 70,000 years of settlement, the slow wobble of the Earth’s axis changed the summer solar radiation in the southern hemisphere, leading to periodic changes in rainfall in southern Africa.
Specifically: the data from the paleoclimatic model suggest that the increase in humidity opened green corridors, first to the northeast and then to the southwest , and these green corridors motivated the exploration of some groups of humans. There were three waves of migration. The first two migrated into both the northwest and southwest corridors; and the third remained in the same region until today. This means that there was an original nucleus that continued to prosper in the region until today.
In turn, the native land of our ancestors had to experience a period of drought, caused by the sustained exploitation of the land during the 70,000 years that the settlement lasted.
“These first migrants left a population of origin. Eventually, they adapted to the drylands and today maternal descendants of the original population can be found in the Kalahari region ,” the researchers explain.
In conclusion: with these data, scientists were finally able to locate the origin of the first anatomically modern ‘Homo sapiens sapiens’ in this region of Africa , south of the Zambezi River, occupied for 70,000 years, and which was followed by a drought that led to the inhabitants had to leave to populate other more humid areas.
More information: Vanessa M. Hayes et al. ” Human origins in a southern African palaeo-wetland and first migrations ” Nature https://doi.org/10.1038/s41586-019-1714-1
