New clues to the origin of domestic horses

Domestic horses likely did not originate in Anatolia as previously suspected, according to a new study of ancient remains dating as far back as 9000 BCE.

Instead, they may have been introduced to the peninsula – which makes up most of modern-day Turkey – and the nearby Caucasus region from the Eurasian Steppe by about 2000 BCE, during the Bronze Age.

The findings, presented in a paper in the journal Science Advances, also suggest imported domestic horses were bred with local wild Anatolian horses and donkeys and provide the earliest genomic evidence for a mule in southwest Asia, dating to between 1100 and 800 BCE.

The research was led by Silvia Guimaraes from the Institut Jacques Monod, Paris, and brought together scientists from France, Germany the US, the Netherlands and Armenia.

Domestication of horses about 5500 years ago forever changed transportation, trade, warfare, and migration, but despite their transformative role in human history, it remains unclear where, when and how many times horses were domesticated.

In particular, Guimaraes and colleagues write, the origin of the domestic horse in Anatolia, and more generally in Southwest Asia, “continues to represent a complex archaeological puzzle”.

In recent years, however, recovery of horse remains from archaeological sites in Anatolia and neighbouring areas, coupled with new technology has made it possible to specifically address the processes responsible for the origins of domestic horses in this part of Asia.

In 2018, a study published in Science, disrupted conventional thinking when it suggested that the horses from the Botai culture of Kazakhstan were not the ancestors of our modern equine companions.

To take things further, Guimaraes and colleagues analysed 111 equid remains from eight sites in central Anatolia and six in the Caucasus dating mostly from the Early Neolithic to the Iron Age (from 9000 to 500 BCE).

They performed both morphological and paleogenetic analyses, scrutinising mitochondrial DNA, Y chromosome DNA, and DNA markers related to coat colour.

They found, they say, that nonlocal genetic lineages still present in domestic horses today suddenly appeared in about 2000 BCE rather than developing gradually over time, as would be expected if these changes emerged within Anatolia.

“We were able to identify mitotypes characteristic of local Anatolian wild horses, which were regularly exploited in the early and middle Holocene,” they write in their paper.

“However, we identified a pattern of genetic change that does not reflect a gradual process involving the local population but rather a sudden appearance ~2000 BCE of nonlocal lineages that are still present in domestic horses.”

Their findings, they suggest, direct attention to nearby Black Sea regions as a more likely origin for domesticated horses.