Genetic analysis of a 40,000-year-old individual from Tianyuan Cave near Beijing, China, has revealed a complex history of population dynamics in Eurasia. The study shows that the Tianyuan individual is more closely related to ancient and present-day East Asians than to Europeans, indicating that the genetic separation between these groups occurred before 40,000 years ago. This finding pushes back the timeline for the divergence of these major human populations and suggests a period of intricate interactions and movements across the continent.
The research, which involved sequencing the ancient human’s genome, provides direct evidence of a structured population in Asia during the Upper Paleolithic. Notably, the Tianyuan individual did not contribute directly to modern Asian populations but belonged to a related group that was part of a broader population landscape. This individual’s genome also shows intriguing connections to a 35,000-year-old individual from Belgium and some Native American populations in South America, highlighting a previously unknown layer of complexity in early human migrations and relationships across Eurasia.
Genetic Ties Across Continents
One of the most surprising findings is the genetic link between the Tianyuan individual and a 35,000-year-old European from the GoyetQ116-1 site in Belgium. The Tianyuan individual shares more genetic material with this specific European individual than with other ancient Europeans of a similar age. This suggests that the separation between early European and Asian populations was not a clean split but likely involved ongoing, albeit limited, gene flow or a shared ancestral population that did not contribute to other ancient Europeans sampled to date.
This connection is further supported by mitochondrial DNA evidence. The GoyetQ116-1 individual carried a mitochondrial haplogroup M, which is common in present-day East and Southeast Asians, Oceanians, and Native Americans but is virtually absent in modern European populations. This shared maternal lineage points to a deep, shared history that challenges simpler models of human expansion out of Africa and across Eurasia. The findings suggest a more interconnected world during the Late Pleistocene than previously thought, with populations moving and mixing over vast geographical distances.
Archaic Ancestry and Its Legacy
The study also examined the proportion of archaic hominin DNA, from Neanderthals and Denisovans, in the Tianyuan individual’s genome. Like other early modern humans in Eurasia, the Tianyuan individual carried a significant amount of Neanderthal ancestry, estimated at 4-5%. This is higher than the 1-2% found in present-day Eurasians, a finding that supports the hypothesis that natural selection has gradually removed some Neanderthal DNA from the modern human gene pool over the last 40,000 years.
The Denisovan Connection
While the analysis did not detect high levels of Denisovan ancestry, such as those found in modern Oceanians, it could not rule out the presence of lower levels comparable to those in mainland Asians today. The limited power of the analysis for detecting small amounts of archaic admixture means that the full extent of Denisovan contribution to the Tianyuan individual’s ancestry remains an open question. Other research indicates that there were likely at least two distinct Denisovan admixture events into modern human populations in Eurasia, suggesting that Denisovans were a widespread and diverse group.
Implications for the Peopling of the Americas
The Tianyuan genome also sheds new light on the settlement of the Americas. The analysis revealed a surprising genetic link between the 40,000-year-old individual and some present-day Native American populations in South America, specifically the Surui and Karitiana in Brazil and the Chane in Argentina and Bolivia. These groups share more genetic similarities with the Tianyuan individual than other Native American populations do.
This finding supports the emerging view that the Americas were populated by at least two distinct founding groups. The genetic affinity between the Tianyuan individual and certain Amazonian populations suggests that a population widespread in East Asia at least 40,000 years ago persisted and contributed to the ancestry of some of the first people to enter the Americas. This ancestral population appears to be distinct from the primary ancestors of other Native American groups, adding another layer to the complex history of the continent’s first inhabitants.
A Subdivided Eurasian Landscape
The combined genomic data from the Tianyuan individual and other ancient humans from the same period paint a picture of a highly structured and diverse human landscape in Eurasia 40,000 years ago. At least four distinct populations coexisted: one ancestral to present-day Europeans, represented by the 37,000-year-old Kostenki14 individual from Russia; a second ancestral to present-day East Asians, to which the Tianyuan individual was related; and at least two other populations, represented by the 45,000-year-old Ust’-Ishim individual from Siberia and the 40,000-year-old Oase1 individual from Romania, who do not appear to have contributed significantly to modern populations.
This evidence demonstrates that the spread of modern humans across Eurasia was not a simple, uniform process. Instead, it involved multiple waves of expansion, complex interactions between different groups, and local extinctions. The Tianyuan genome is a crucial piece of this puzzle, revealing deep connections across Asia and even into Europe and the Americas, and underscoring the dynamic nature of human population history during the Late Pleistocene.
Future Research Directions
The study of the Tianyuan individual highlights the power of ancient DNA to resolve longstanding questions about human prehistory. However, it also raises new questions. Future research will need to focus on recovering more ancient genomes from across Asia to better understand the population to which the Tianyuan individual belonged and its relationships with other ancient and modern groups.
Clarifying the timing and extent of gene flow between early Asian and European populations will be a key area of investigation. Additionally, further studies are needed to determine the precise nature of the Denisovan contribution to mainland Asian populations and to unravel the full complexity of the ancestral lineages that gave rise to the first peoples of the Americas. The ongoing discovery and analysis of ancient human remains will continue to refine our understanding of our species’ journey across the globe.