Genetics and the African Past

Abstract

Africa harbors the greatest human genetic diversity on the planet, a fact that has inspired extensive investigation of the population structure found across the continent and the demographic processes that shaped observed patterns of genetic variation. Since the 1980s, studies of the DNA of living people have repeatedly demonstrated that Africa is the cradle of human origins, in agreement with fossil and archaeological evidence. Since the first ancient human genome was published in 2010, ancient DNA (aDNA) has contributed additional possibilities for exploring population history, providing a direct window into genetic lineages that no longer exist or are barely discernible. Genetic data from both living and ancient people—when integrated with available archaeological, bioarchaeological, historical linguistic, and written or oral historical data—are important tools for contextualizing African genetic diversity and understanding the biological and cultural processes that have shaped it over time. While most studies to date have focused on humans, aDNA can also be obtained from plant and animal remains, sediments, and some artifacts, all of which can enable a more comprehensive understanding of human lives. Genetic research on the African past often focuses on human origins and Pleistocene population structure, as well as on the origins, directionality, and tempo of demographic changes that accompanied Holocene transitions to herding and farming. The rise of cosmopolitan cities and states in the past two millennia has been examined with genetic evidence to a very limited extent, but this is a potentially rich vein of research. Increasingly, forced migrations of enslaved Africans and the development of the diaspora are the subjects of genetic study as well. Yet to date, Africa remains vastly understudied relative to parts of the world such as Eurasia, in terms of both ancient and present-day DNA. This shapes not only the study of the past but also medical innovations and public health. While the bulk of published African genomes come from present-day people, there are problems with relying solely on this data to reconstruct the past, given the continent’s long and complex demographic history. Increasingly, aDNA is providing novel perspectives on a past largely invisible in the genomes of people living in the 20th and 21st centuries due to recent demographic shifts. A surge in African aDNA studies since 2015 has also renewed longstanding debates about the ethics of genetic research on people, both living and deceased. Researchers working in Africa today must consider ethical issues including stakeholder engagement, informed consent, and control of biological samples and data; in aDNA studies, descendant communities, museum curators, bioarchaeologists, and geneticists, among others, play critical roles in these discussions.