The term “West Eurasians” refers to a broad cluster of human populations primarily found in Europe, the Middle East (West Asia), and parts of Central and South Asia, along with their descendants globally. This classification is rooted in population genomics, which analyzes genetic similarities and differences to understand human population history. Studying West Eurasians provides insights into ancient migrations, the spread of technologies like agriculture, and the complex genetic intermingling that shaped human diversity across a vast geographical expanse.
Defining West Eurasia
West Eurasia encompasses a vast geographical area stretching from Europe across to the Middle East and extending into parts of Central and South Asia. Genetically, populations within this region share a closer relationship with each other than with populations from East Asia or Africa. This grouping is based on shared ancestry and specific genetic markers, largely tracing back to Paleolithic Middle Eastern populations. While there is high genetic similarity across West Eurasia, studies show a gradual genetic structure influenced by geography, with observable separations between Europeans and West Asians. For example, the island of Sardinia shows a distinct genetic profile, while other clusters correspond to populations in the Caucasus and Arabia.
Ancient Ancestral Components
The genetic makeup of West Eurasians is a mosaic of contributions from several ancient human populations.
One such group is the Western Hunter-Gatherers (WHG), who emerged from a refugium in Europe after the Last Glacial Maximum, around 20,000 years ago. These Mesolithic hunter-gatherers were a significant ancestral component in Europe. Although their lineage does not survive as a majority contribution in any modern population, WHG ancestry can be modeled as a component in most contemporary Europeans.
Another major contributor was the Early European Farmers (EEF), who originated from Anatolia (Asia Minor) and brought agriculture to Europe beginning around 7,000 BC. These farmers largely replaced the native WHGs across Europe, though some limited admixture occurred. Their genetic profile is most similar to modern Southern Europeans, particularly Sardinians.
The Ancient North Eurasians (ANE) represent an older, distinct genetic group that emerged from an admixture of early West Eurasian and East Eurasian lineages during the Upper Paleolithic period. This population contributed ancestry to a wide range of populations across Eurasia. ANE ancestry is found in nearly every European group studied.
The Western Steppe Herders (WSH), often referred to as Yamnaya ancestry, played a significant role in shaping West Eurasian genetics, particularly during the Bronze Age. This ancestral component originated from a merger of Eastern Hunter-Gatherers (EHG) and Caucasus Hunter-Gatherers (CHG) in roughly equal proportions. EHGs, found in Eastern Europe, themselves carried a substantial amount of ANE ancestry along with some WHG ancestry. CHGs, native to the Caucasus and northern Iran, also contributed significantly to the Yamnaya and later to populations in Central and South Asia.
Major Migrations and Their Impact
Significant migratory events profoundly reshaped the genetic landscape of West Eurasia. The spread of agriculture from Anatolia into Europe, starting around 7,000 BC, represents a major demographic shift. Farming was introduced by migrating populations from the Near East who carried their agricultural knowledge and their genes into Europe. Early European Farmers (EEF) expanded across the continent, largely replacing the indigenous Western Hunter-Gatherers (WHG). While hunter-gatherer genes persist, their overall genetic profile in modern Europeans was profoundly impacted by this influx.
Following the agricultural expansion, the Bronze Age witnessed further large-scale population movements, particularly from the Pontic-Caspian steppes. Around 3,000 BC, people of the Yamnaya culture, or closely related groups, embarked on a massive expansion across Eurasia. Their migrations brought significant genetic changes, with WSH ancestry becoming higher in Northern Europe and lower in Southern Europe.
The Yamnaya expansion is also strongly associated with the dispersal of Indo-European languages across large parts of Eurasia. As they moved, Yamnaya-related populations admixed with local Neolithic communities, forming new cultural groups such as the Corded Ware and Bell Beaker cultures in Europe. This period of intense migration and admixture laid much of the genetic groundwork for present-day Eurasian populations.
Modern Genetic Landscape
The ancient ancestral components and migratory events have culminated in the diverse genetic patterns seen in modern West Eurasian populations. Today’s Europeans, for example, are largely modeled as a mixture of Western Hunter-Gatherers (WHG), Early European Farmers (EEF), and Western Steppe Herders (WSH), with varying proportions across different regions. The contribution of EEF ancestry is more pronounced in Mediterranean Europe, diminishing towards northern and northeastern Europe, where WHG ancestry tends to be stronger.
The genetic structure of Europe and Central Asia by the end of the Bronze Age closely resembled the present-day Eurasian genetic landscape. While modern Eurasian populations are genetically closer to Bronze Age groups than to earlier Mesolithic or Neolithic populations, southern European populations maintain stronger genetic links to Neolithic farmers. Genetic differences between ancient West Eurasian populations were considerably higher than those observed in contemporary populations.
Recent admixture events have further contributed to the contemporary genetic landscape. Admixture from outside West Eurasia, such as East Asian ancestry, is also visible in West Central Asian, Caucasus, and Turkish populations. This continuous interplay of ancient lineages and subsequent migrations has resulted in the complex, mosaic-like genetic diversity observed across modern West Eurasian groups today.