Ancient Basal Eurasians represent a distinct lineage of early modern humans, whose discovery reshaped our understanding of human genetic history outside of Africa. Their unique genetic signature revealed a previously unknown component of ancestry present in many populations today.
Defining Basal Eurasians
Basal Eurasians are a deeply divergent lineage of modern humans, meaning they branched off from other non-African populations at a very early stage. This split is estimated to have occurred roughly 60,000 to 100,000 years ago, even before other non-African groups diversified from one another. A distinguishing genetic feature of Basal Eurasians is their reduced, or even absent, Neanderthal admixture compared to other ancient non-Africans. This reduced Neanderthal ancestry suggests that the Basal Eurasian lineage diverged before the main interbreeding events between modern humans and Neanderthals, which are thought to have occurred approximately 50,000 to 60,000 years ago.
While no direct ancient remains of a “pure” Basal Eurasian individual have been identified, their existence is inferred from the genetic makeup of later populations. They are considered a “ghost” population, leaving their traces in the genomes of their descendants.
Discovery Through Genetic Analysis
The existence of Basal Eurasians was not evident from archaeological findings but was revealed through advanced genetic analysis of ancient human DNA. Scientists utilized computational genetic methods to model the ancestral components of modern European populations. This research indicated that early European farmers carried ancestry from a previously unknown non-African population, which was subsequently named “Basal Eurasians”.
Further studies provided more evidence for this lineage by observing that populations with higher proportions of Basal Eurasian ancestry also exhibited lower levels of Neanderthal DNA. This finding supported the hypothesis of a deeply divergent lineage that had little to no contact with Neanderthals before mixing with other Eurasian groups. The genetic evidence, particularly the unique pattern of Neanderthal admixture, allowed researchers to infer the presence and characteristics of this ancient population.
Their Place in Human Migration
Basal Eurasians are thought to have originated in the Southern Middle East, possibly in Prehistoric Arabia or North Africa. Their presence reshapes the narrative of human migration out of Africa, suggesting a more complex initial dispersal into Eurasia. This lineage likely diverged from other Eurasians shortly after the “Out of Africa” event, possibly remaining isolated in regions like the South Levant and Arabian Peninsula due to ecological factors.
While initially isolated, Basal Eurasians began to mix with other populations by at least 25,000 years ago. This admixture influenced the genetic landscape of ancient peoples, with their ancestry becoming widespread in populations inhabiting Western Asia and the Eastern Mediterranean. For instance, ancient Near Eastern populations, such as Natufian hunter-gatherers and early farmers from the Levant and Zagros Mountains, show significant proportions of Basal Eurasian ancestry.
Genetic Legacy in Modern Populations
The genetic signature of Basal Eurasians can be traced in various modern human groups, particularly within West Eurasian populations. Modern populations in the Levant, for example, derive between 35-38% of their ancestry from Basal Eurasians, while modern Anatolians and people from the Caucasus show percentages between 25-30%. Modern Europeans typically carry around 20% or less of this ancestry.
This Basal Eurasian component is also proposed to explain why modern West Eurasians generally have lower levels of Neanderthal ancestry compared to East Eurasians. It suggests that the Neanderthal genetic contribution in West Eurasians was diluted through admixture with Basal Eurasian groups, who carried little to no Neanderthal DNA. The spread of agricultural practices during the Neolithic Revolution further disseminated Basal Eurasian ancestry throughout West Eurasia, demonstrating their lasting influence on global genetic diversity.