Backbone, good temperament were key features of horses that swept the world

A view of the animal slaughter unearthed in the courtyard of the building at Casas-del-Turuñuelo.
A view of the animal slaughter unearthed in the courtyard of the building at Casas-del-Turuñuelo.

A better temperament and a strong backbone appear to have been the key features of horses in the northern Caucasus region that ultimately led to their global domination.

A large group of researchers, who conducted the largest genetic study of horses to date, have found that all current domestic horses descend from those first domesticated in the steppes north of the Caucasus.

In the centuries that followed, the horses spread to other regions of Asia and Europe.

The study, reported this week in the journal Nature, brings to an end a long-standing debate about the location and chronology of the earliest documented evidence of domestication of the horses that gave rise to today’s populations.

The research also answers questions about when this domestication process began to spread to other regions of the world, thus replacing other types of horses that existed at the time.

The study involved a team of 114 institutions and 162 researchers specialising in archaeology, palaeogenetics and linguistics, led by Professor Ludovic Orlando, with the French science agency CNRS.

Orlando is the principal investigator of the ERC-PEGASUS project, which, together with France Genomique-Projet Bucéphale, financed the research.

The study involved sequencing the genomes of 273 remains of horses that inhabited various regions of Eurasia in a chronological arc extending from 50,000 years ago to 200 BC.

The genetic information was then compared to the genomes of modern domestic horses.

Analysis determined that, between 2200 BC and 2000 BC, a drastic change took place in which the genetic profile existing in the Pontic steppes began to spread beyond its region of origin, thus replacing in a few centuries all wild horse populations from the Atlantic to Mongolia.

“This replacement in the genetic composition of Eurasian populations is associated with significant genomic differences between this new type of horse and the horses of the populations that disappeared,” Orlando said.

“On the one hand, this new type of horse from the steppes of the northern Caucasus had a more docile behaviour and, on the other hand, a more robust constitution in the vertebral skeleton.”

The researchers suggest that these characteristics triggered the successful selection of these animals, at a time when horse travel was becoming widespread in Eurasia.

First author Pablo Librado, also with CNRS, said the study showed that the distribution of this new type of horse in Asia coincided with the appearance of light carts and the spread of Indo-Iranian languages.

In contrast, the migration of Indo-European populations from the steppe zone to the heart of Europe during the third millennium BC did not use this new type of horse as a vector for its expansion. This result demonstrates the importance of also incorporating the genetic history of animals when analysing the dimension of human migrations and intercultural contacts”.

The individuals analysed include equids from various sites on the Iberian Peninsula, including Casas del Turuñuelo in Guareña, Badajoz; and Cova Fosca, in Alt Maestrat, Castelló.

Cova Fosca was excavated by Francesc Gusi and Carmen Olaria.

Olaria, professor of prehistory at the Jaume I University in Spain and a co-author of this study, says Cova Fosca has a very rich Holocene archaeozoological record.

“We were able to identify horse remains in ancient Neolithic levels, a very rare taxon in Iberian sites from this period.

“This uniqueness allowed us to publish years ago, together with Jaime Lira Garrido and Juan Luis Arsuaga, the first mitochondrial sequences of horses from this site.”

They found a unique mitochondrial lineage exclusive to Iberia that currently appears in very few horses, all of which are Iberian or of Iberian origin.

Casas del Turuñuelo is one of the most impressive archaeological discoveries in the region in recent years.  It is an architectural complex from the middle of the first millennium BC belonging to the Tartessos culture, where researchers found the biggest sacrificial burial site documented to date in a site of Mediterranean protohistory.

This mass slaughter site is notable for the large number of equids found in the courtyard area.

Genetically, the horses stand out. Researcher JaimeLira Garrido says the latest work led by Orlando has also allowed local researchers to delve deeper into the evolutionary history of Iberian horses.

“In a previous study, Orlando and his team discovered that a genomic lineage developed on the Iberian Peninsula that is now extinct and very different from the rest of the ancient and modern Eurasian horse lineages described to date.

“The evolutionary origin of this lineage and the causes that led to its disappearance are still unknown.

“However, we have been able to identify in the Neolithic sample from the Cova Fosca the oldest evidence of this extinct lineage; and that the Turuñuelo Equid 4 was, nevertheless, a descendant of this new type of horse that was so rapidly distributed throughout the known world some 4000 years ago.”

Librado, P., Khan, N., Fages, A. et al. The origins and spread of domestic horses from the Western Eurasian steppes. Nature (2021).

The study, published under a Creative Commons License, can be read here.

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