DNA points to human origins in Southern Africa

By ALLISON CHEN | April 4, 2019

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PUBLIC DOMAIN Although not conclusive, mitochondrial DNA evidence puts the earliest humans in Southern Africa.

When did humans as a species become what we today would recognize as human? 

Researchers from the University of Huddersfield and the University of Cambridge, both in the United Kingdom, as well as the University of Minho in Portugal have reported evidence that populations exhibiting modern human behavior and culture may have originated in Southern Africa, expanding afterward throughout the world. Their findings were published in the journal Scientific Reports. 

Previous hypotheses for the location of origin of modern humans have involved all parts of Africa, including the Southern, Eastern and Central regions. 

The researchers on the paper in Scientific Reports included teams of geneticists at the University of Huddersfield and the University of Minho, as well as an archaeologist from the University of Cambridge, Professor Sir Paul Mellars. 

They identified a small-scale migration that occurred approximately 65,000 years ago, with individuals from Southern Africa moving into East Africa. 

Evidence for early societies with modern features were previously identified along the South African coastline. The identifying features of these sites include potential use of symbols and ornaments, such as drawings and shell beads, as well as evidence of technological advancement, such as bone tools and a toolkit for processing ochre, a pigment. Some of these date to approximately 100,000 years ago. 

Types of artifacts, including certain distinctive geometric stone tools, similar to those found in regions in modern-day South Africa, have also been identified in East Africa. 

These objects in both regions date back to around the same time, suggesting migration from one region to another. However, it was previously difficult to determine the direction of the migration. 

To get a better understanding of the path humans took in migrating around the globe, the researchers studied mitochondrial DNA lineages from Southern Africa and other regions of Sub-Saharan Africa. They also looked at over one million single-nucleotide polymorphisms in whole genomes to determine whether autosomal DNA evidence supported evidence from mitochondrial DNA. 

Simulations performed by the researchers rejected models that did not involve migration from Southern to Eastern Africa. However, the simulations could not determine whether the movement was unidirectional or bidirectional, in other words whether the movement was only from Southern to Eastern Africa or whether it occurred the other way around as well. 

While the researchers found evidence of migration in mitochondrial DNA, they did not find any similar indications in their genome-wide studies. They explained that this was likely due to recombination.

The movement may have been facilitated by a period of humid climate across Africa, coming after a long drought that left regions largely arid and isolated. Indeed, the genetic evidence that the researchers uncovered indicates a migration around 70,000-60,000 years ago, which correlates with this humid period. 

The researchers noted that Southern African groups nevertheless likely did not serve as a major direct genetic source for humans living today. That distinction likely belongs to populations from Eastern Africa. 

Rather, it is more plausible that technological advances and cultural advances such as symbology were spread from Southern African populations to Eastern African ones. These new, changed populations then may have served as the source for migrations across the rest of the world. 

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