Ajeje Brazorf
09-20-2024, 02:07 PM
https://www.nature.com/articles/s41559-024-02532-3
This study explores the genetic history of southernmost Africa over 9,000 years, focusing on the Oakhurst Rockshelter site, which contains skeletal remains from different periods throughout the Holocene. Here are the specific findings:
1. Time Frame and Sampling: The study examines genome-wide sequences from 13 individuals recovered from Oakhurst Rockshelter, located near George, South Africa. The remains span from around 10,000 to 1,300 years before present (BP), providing insights into the population history of the San people. Nine of these individuals had sufficient ancient DNA (aDNA) for detailed genetic analysis.
2. Genetic Continuity: The research demonstrates that southernmost Africa, particularly the Oakhurst region, experienced genetic continuity over 9,000 years. Unlike many other regions in the world, which saw population replacements or significant admixture events, the ancient inhabitants of Oakhurst maintained genetic stability throughout the Holocene, even as other areas were affected by waves of migration.
3. San Ancestry: The San populations, specifically the ‡Khomani and Karretjiemense groups in South Africa, still carry significant genetic links to the ancient hunter-gatherers from Oakhurst. This genetic continuity is particularly notable because it persisted despite later admixture from non-Southern African populations.
4. Archaeological Context: The study connects the genetic data to archaeological findings, such as the lithic (stone tool) traditions at Oakhurst. Initially, the site featured macrolithic tools, typical of the Oakhurst technocomplex (~10,000 BP). Around 8,000 BP, there was a shift to microlithic tools of the Wilton complex, which persisted through the Middle and Later Holocene, suggesting cultural continuity alongside the genetic stability.
5. Admixture Events: The study also explores the impact of pastoralism and farming, which introduced new genetic material from northeastern Africa and West Africa into southern African populations around 2,000 years ago. However, the Oakhurst individuals did not show evidence of this admixture until after 1,300 BP, suggesting that these external influences arrived later in southernmost Africa compared to other regions. Present-day San populations have about 9% genetic admixture from non-San sources, obscuring the ancient genetic structure, but the link to the ancient Oakhurst population remains intact.
6. Unique Genetic Signature: The ancient DNA data shows that the Oakhurst individuals have a genetic profile that is basal to all other modern human populations, reflecting the deep human history of the San people. The study highlights that San populations exhibit three distinct ancestry components: northern San, central San, and southern San, with the Oakhurst individuals clustering with the southern San.
7. Demographic Stability: The researchers tested for population continuity through methods like F3 and F4 statistics, showing that Oakhurst populations were genetically similar to both earlier and later groups from the same region. They did not exhibit signs of genetic isolation, as their genetic diversity levels were comparable to those of other African hunter-gatherers.
8. Late Disruptions: While Oakhurst shows remarkable genetic stability for thousands of years, the genetic landscape of southernmost Africa was later altered by the arrival of pastoralist and farming communities after 1,300 BP, and further disrupted by European colonization after 1650 AD. Despite these disruptions, some modern San groups still preserve significant genetic continuity with the ancient populations of Oakhurst.
This study explores the genetic history of southernmost Africa over 9,000 years, focusing on the Oakhurst Rockshelter site, which contains skeletal remains from different periods throughout the Holocene. Here are the specific findings:
1. Time Frame and Sampling: The study examines genome-wide sequences from 13 individuals recovered from Oakhurst Rockshelter, located near George, South Africa. The remains span from around 10,000 to 1,300 years before present (BP), providing insights into the population history of the San people. Nine of these individuals had sufficient ancient DNA (aDNA) for detailed genetic analysis.
2. Genetic Continuity: The research demonstrates that southernmost Africa, particularly the Oakhurst region, experienced genetic continuity over 9,000 years. Unlike many other regions in the world, which saw population replacements or significant admixture events, the ancient inhabitants of Oakhurst maintained genetic stability throughout the Holocene, even as other areas were affected by waves of migration.
3. San Ancestry: The San populations, specifically the ‡Khomani and Karretjiemense groups in South Africa, still carry significant genetic links to the ancient hunter-gatherers from Oakhurst. This genetic continuity is particularly notable because it persisted despite later admixture from non-Southern African populations.
4. Archaeological Context: The study connects the genetic data to archaeological findings, such as the lithic (stone tool) traditions at Oakhurst. Initially, the site featured macrolithic tools, typical of the Oakhurst technocomplex (~10,000 BP). Around 8,000 BP, there was a shift to microlithic tools of the Wilton complex, which persisted through the Middle and Later Holocene, suggesting cultural continuity alongside the genetic stability.
5. Admixture Events: The study also explores the impact of pastoralism and farming, which introduced new genetic material from northeastern Africa and West Africa into southern African populations around 2,000 years ago. However, the Oakhurst individuals did not show evidence of this admixture until after 1,300 BP, suggesting that these external influences arrived later in southernmost Africa compared to other regions. Present-day San populations have about 9% genetic admixture from non-San sources, obscuring the ancient genetic structure, but the link to the ancient Oakhurst population remains intact.
6. Unique Genetic Signature: The ancient DNA data shows that the Oakhurst individuals have a genetic profile that is basal to all other modern human populations, reflecting the deep human history of the San people. The study highlights that San populations exhibit three distinct ancestry components: northern San, central San, and southern San, with the Oakhurst individuals clustering with the southern San.
7. Demographic Stability: The researchers tested for population continuity through methods like F3 and F4 statistics, showing that Oakhurst populations were genetically similar to both earlier and later groups from the same region. They did not exhibit signs of genetic isolation, as their genetic diversity levels were comparable to those of other African hunter-gatherers.
8. Late Disruptions: While Oakhurst shows remarkable genetic stability for thousands of years, the genetic landscape of southernmost Africa was later altered by the arrival of pastoralist and farming communities after 1,300 BP, and further disrupted by European colonization after 1650 AD. Despite these disruptions, some modern San groups still preserve significant genetic continuity with the ancient populations of Oakhurst.