For millennia, a distinct genetic lineage has persisted in the central Southern Cone of South America – particularly in Argentina – representing a previously unknown population that remained remarkably isolated for at least 8,000 years. A new study led by Harvard University researchers unveils this “ghost population,” adding a crucial piece to the puzzle of early human migration and genetic diversity in the Americas.
The Last Frontier of Human Expansion
South America, especially its southernmost regions, was among the last places reached by humans as they spread across the globe. Archaeological evidence suggests initial presence dating back around 14,000 years, although the exact timeline remains debated. Despite this, ancient DNA analysis from this region has been scarce – until now. The new research significantly expands the available genetic data, analyzing samples from 238 ancient individuals spanning 10 millennia.
A Persistent Genetic Signature
The study reveals a lineage of humans first appearing approximately 8,500 years ago, which became dominant in the central Southern Cone by around 4,600-150 years ago. This group exhibited minimal genetic mixing with neighboring populations during the Middle Holocene, despite coexisting with two other distinct genetic lineages. DNA analysis from a 10,000-year-old individual in the Pampas region shows that genetic differentiation was already underway, suggesting long-term isolation.
Isolation Despite Diversity
The researchers were surprised to find such genetic consistency in a region known for its linguistic and cultural diversity. The data suggests that despite developing unique cultures and languages, these people remained biologically isolated. This raises questions about the conditions that facilitated such prolonged genetic separation: geographic barriers, cultural practices, or limited inter-group contact may have played a role.
Implications for Understanding Human History
The expanded dataset promises further insights into the ancient history of Argentina. Advanced DNA technology now allows for detailed mapping of population size changes and migration patterns, similar to those already established for Europe. By analyzing ancient DNA at a fine scale, archaeologists can uncover previously inaccessible demographic information about past populations.
“With large ancient DNA sample sizes, it is possible to learn details about the questions that really matter… about how people are related to each other at a fine scale,” explains Harvard geneticist David Reich.
This discovery underscores the importance of ancient DNA in reconstructing human history, particularly in regions where archaeological records are incomplete. The findings demonstrate that even in areas with apparent cultural complexity, underlying genetic patterns can reveal surprising stories of long-term isolation and persistence.
