Nestled in a valley on the southern coast of South Africa, the Oakhurst rock shelter is a treasure trove of human history. This archaeological site, carved into a sandstone cliff overlooking a stream, has been a witness to human life for an astounding 12,000 years. Archaeologists have unearthed a wealth of evidence, from rock art and stone tools to ceramic fragments and the remains of 46 individuals. The discovery of these remains is especially significant because most very old burials found in South Africa (from the last 40,000 years) have been of single individuals.
New technological advancements are allowing researchers to delve deeper into the past than ever before. One team of researchers, focusing on the Oakhurst site, embarked on a mission to reconstruct the genomes of its ancient inhabitants, tracing their genetic lineage to modern populations in the region. A genome, essentially a blueprint of an organism, carries genetic information passed down through generations, creating a tangible record of history.
This field of study, known as archaeogenetics, helps us understand the movements of populations and the history of humankind. At Oakhurst, researchers successfully generated 13 ancient genomes from skeletal remains. Two individuals, dating back approximately 10,000 years, provided the oldest ancient DNA ever discovered in the region. The analysis revealed a distinct population history for southernmost Africa, unlike other regions of the world. Unlike other regions where populations have arrived in waves, replacing or mixing with existing groups, the Oakhurst research shows a remarkable genetic continuity spanning 12,000 years, from 10,000 years ago to as recently as 1,300 years ago.
While archaeogenetics has shed light on human history in Asia and Europe, the field has faced challenges in Africa due to the warm climate, which degrades ancient DNA. To date, fewer than two dozen genomes from South Africa, Botswana, and Zambia have been published. This is a significant gap in our understanding of human history, given that Africa boasts the greatest human genetic diversity in the world, with the rest of the world’s genetic diversity representing a subset of Africa’s. Studying African genetic history is crucial to understanding the complete story of humanity.
The Oakhurst study, launched in 2017, involved a team of anthropologists, archaeologists, and archaeogeneticists. After obtaining the necessary permissions, they carefully sampled 13 individuals from the site. These individuals, spanning different time periods, were dated using radiocarbon dating of bone or tooth collagen. The genetic analysis was particularly challenging due to the poor preservation of DNA. However, researchers persevered, extracting DNA from powdered skeletal material and using laboratory techniques to multiply and sequence the DNA molecules.
The results revealed that all the genomes were remarkably similar to those of modern-day San and Khoekhoe people who inhabit the region, including the ǂKhomani San. This finding indicates that between 10,000 and 1,300 years ago, no ancestry from outside present-day South Africa entered the Oakhurst rock shelter. This long-term genetic continuity is a striking contrast to the dynamic changes observed in ancient DNA records in Europe and Asia, where major population movements have left their mark.
While genetic continuity prevailed, the Oakhurst site also reveals evidence of cultural evolution. Changes in stone tool technology, observed at Oakhurst, align with similar shifts seen across other archaeological sites in South Africa. Around 2,000 years ago, a new wave of people arrived in the region, bringing herding, farming, and new languages. Interactions between these newcomers and the local hunter-gatherer groups ensued, but even the individual who lived 1,300 years ago, the most recent analyzed in the study, shared genetic similarities with their ancestors from thousands of years prior.
These groundbreaking findings offer a glimpse into the remarkable stability of the genetic history of southernmost Africa, challenging our understanding of human population movements. They open new doors for further exploration into one of the world’s most diverse regions in terms of culture, language, and genetics.
