Ancient DNA Explains Human Origins and Prehistory
By Bradley Fox, ‘21
Source: Wikimedia Commons
Caption: Researchers at Harvard Medical School recently sequenced DNA samples from 15 humans from Sub-Saharan Africa to reconstruct the distribution and diversification of humans across the African continent between 1,000-8,000 years ago.
Genetic information from fifteen different Ancient African individuals living between 1,000 and 8,000 years ago has given modern researchers key information on the migration patterns of ancient humans (1, 2). A recent study, released in the journal Cell on September 21, explains how DNA samples extracted from prehistoric humans’ remains were used to understand how some of our oldest ancestors lived and adapted to ancient environments (1).
The study featured three ancient DNA samples from Southern Africa, seven from modern Malawi, one from modern Ethiopia and another five from Western and Central Africa (2). Each sample was sequenced by a team including David Reich and Pontus Skoglund, two current professors at the Harvard School of Medicine who had “colleagues in archaeology who were interested . . . and had suitable samples” (2).
After sequencing, they compared the DNA to that of 584 present-day individuals from over 50 ethnic groups on the African continent (2). They also included genomes from 300 individuals in 142 populations across the rest of the world (2).
Their data revel stunning insights on the distribution of humans in prehistoric Africa. Populations related to indigenous people in modern South Africa, for instance, came from an “ancestry of Malawi [and Tanzanian] hunter-gatherers from 8,100 to 2,500 years ago” (12). The movement of West African agriculturalists to Malawi and Tanzania, researchers hypothesize, played a key role in the displacement of hunter-gatherer populations to the South (1).
Researchers were even more intrigued, however, to find DNA sequences that supported the idea that ancient African environments allowed for “the earliest diversification of modern human lineages” (2). In South African samples, researchers found evidence for selection on genes coding for taste receptors, implying that adaptive evolution allowed these hunter-gatherers to avoid poisonous plants. Another sample from the Kalahari Desert showed that populations here displayed similar adaptive patterns to genes influencing the skin’s response to ultraviolet light (1).
All across prehistoric Africa, populations were gradually adapting to different environments in a way that supported their specific needs and enhanced survival. What seems more profound than the biological processes of adaption and evolution, however, is the fact that present-day researchers were able to reconstruct evaluate such processes thousands of years after their occurrence.
- Skoglund et al. “Reconstructing Prehistoric African Population Structure”. Cell, 2017 DOI: 10.1016/j.cell.2017.08.049
- Cell Press. (2017, September 21). Ancient DNA data fills in thousands of years of human prehistory in Africa. ScienceDaily. Retrieved September 23, 2017 from www.sciencedaily.com/releases/2017/09/170921141311.htm