Human Evolution and Health: DNA from contemporary Africans can help unravel human history and its health implications

Africa has the highest genetic diversity in the world. In the past, genetic research has mostly focused on European and Asian populations, leaving African populations underrepresented. Despite facing significant health challenges from infectious diseases and non-communicable diseases such as diabetes, cardiovascular disorders, and certain types of cancer, many African countries have been overlooked with regards to genetic research. It is crucial to study African genomes to better understand African human history and improve health outcomes through precision and preventative medicine.

A study funded by the NRF highlighted the critical role that DNA from contemporary Africans can play in understanding deep human history and its health implications. By integrating the genetic data of a large number of contemporary individuals and groups, researchers aimed to better understand human evolution.

The researchers sequenced the whole genomes of individuals from four African populations: the Nama from South Africa; the Mende from Sierra Leone; the Gumuz from Ethiopia; and agriculturalists from eastern Africa. British individuals were included to account for recent gene flow, and a high-coverage ancient Neanderthal genome was also analysed to consider gene flow from Neanderthals. The study used this diverse genetic data to infer demographic models.

The analysis revealed that simple tree-like models are inadequate for explaining human evolution. Instead, the researchers proposed a “tangled vine” model with weakly separated offshoots, indicating continuous genetic exchange among early human populations. This model suggests major lineages in southern, eastern, and western/central Africa during the late Middle Pleistocene, followed by fragmentation and subsequent merging of subpopulations. The study highlighted significant gene flow in western and central Africa during the Last Glacial Maximum.

In their conclusion, the researchers challenge traditional single-origin models of human evolution and emphasise the complexity of human genetic history. The findings suggest that the Middle to Late Pleistocene was a critical period for human evolution, marked by significant genetic exchanges influenced by environmental changes. The study also underscores the importance of including diverse African genomes in research to better understand human history and improve health outcomes.