All domestic horses living on the planet today, whether they are racehorses, ponies, or draft horses, originated from the southern Russian steppes at the end of the third millennium BC. However, the exact timing of the domestication of modern-type horses and their widespread distribution among the ancient populations of Eurasia remains a subject of heated debate.

A new study published on 06/06/2024 in the journal Nature asserts that the spread of domestic modern-type horses began approximately 4,200 years ago. The established date marks the beginning of a new era in human history, when horses significantly accelerated the development of communication networks on the Eurasian continent, acting as a catalyst for unprecedented exchange and interaction between different cultures. This work was coordinated by Ludovic Orlando, director of the Center for Anthropobiology and Genomics at the University of Toulouse, and involved 133 researchers from 113 institutions worldwide, including Toraighyrov University and several other Kazakhstani universities. The research group assembled an extensive collection of archaeological finds of horses from across the Eurasian continent. The study combined results from radiocarbon dating and sequencing of ancient DNA to determine the timing of the existence of genomic lineages, in order to dissect in detail the onset of genetic transformations coinciding with the emergence of horse husbandry.

"I started working with horses about ten years ago. At that time, we only had a few ancient genomes. Thanks to this work, we now have hundreds of them. It was particularly important to obtain data from Central Europe, the Carpathians, and Transylvania, as this area was central to ongoing debates about the origin of horseback riding, which led to the onset of mass migrations from the steppes about 5000 years ago, and possibly earlier," said Pablo Librado, the first author of the study and now a staff scientist at the Institute of Evolutionary Biology in Barcelona (a joint center of CSIC and Pompeu Fabra University).

The research group meticulously examined data on three indicators of horse husbandry. Firstly, the spread of the ancestors of modern horses beyond the region of domestication was traced. Then, the demography of horses during the third millennium BC was reconstructed to precisely determine the timing of the appearance of the very first signs of domestication and the onset of large-scale horse breeding. As a result, evidence of significant changes in the reproductive lifespan of horses was discovered, indicating intentional manipulation of animal reproduction by early breeders. The coincidence of all three lines of evidence dates back to approximately 4,200 years ago. It can be hypothesized that at this time, domestic horses began to be bred in sufficient numbers to meet the growing demand on the continent. Thus, 4200 years ago marked the beginning of intensive horseback movements as we know them. The horse, as a means of transportation, remained the fastest mode of land transport until the advent of mechanical engines in the 20th century.

Nevertheless, ancient DNA studies have revealed earlier changes in the genetic landscape of Europeans, occurring in the first half of the third millennium BC, following the mass expansion of people from the steppes, who are considered carriers of the Proto-Indo-European language. Since the genetic map of horses began to change much later, the research group does not consider horseback riding as the driving force behind the success of these migrations, despite the fact that horse-related terminology forms a common basis for most Indo-European languages.

"One question that has puzzled me for many years concerns the scale of production: how could such a significant number of horses be suddenly produced in a relatively small domestication area to meet the increasingly global demand around the turn of the second millennium BC? Now we have an answer. Breeders were so successful in controlling animal reproduction that they almost halved the time interval between two generations. In other words, they were able to accelerate the breeding process, effectively doubling productivity," added Ludovic Orlando.

The methodology developed in this study for measuring generation time is novel and harnesses the full potential of ancient genome time series. As genomes evolve, they accumulate mutations and recombine with each generation. The number of mutations they carry and the DNA crossover events they undergo serve as a direct measure for the number of generations leading up to them. Combined with radiocarbon dates, the number of generations can be converted into calendar years. The research group found that over the past two centuries, more generations have accumulated, coinciding with the emergence of many modern pedigrees as a result of intensive selective breeding. Remarkably, about 4200 years ago, it was found that the generational clock was ticking faster, precisely at the time when mass production and geographical distribution of domestic horses began.

“Our methodology for measuring temporal changes within a generation has great potential. It “equips” the archaeozoological toolkit with a new way to monitor the development of controlled breeding of various domestic species along with horses. But it can also help shed light on the life span of one generation in ancient populations or animals and how these intervals evolved together with changes in lifestyle or significant climate changes,” adds Pablo Librado, who developed the statistical framework.

Regarding horses, it should be noted that the research group has established the existence of an exceptionally short interval between generations within the development line of horses of the modern type. What significantly distinguishes them is the horses studied at the settlements of Botai (where facts of horse milking, harnessing and corrals were recorded) and Borly 4 in Central Asia. Since the genetic composition of Botai-type horses remained local and did not spread throughout Eurasia, it can be said that the “Botai” did not undertake extensive long-distance migrations.

“Our data confirms two domestications of horses. The first occurred about 5,500 years ago in Northern Kazakhstan. The goal of this process was to solve the problem of declining horse numbers and provide food for the populations inhabiting the steppes of Central Asia. The domestic horse, as we know it, arose about 4,200 years ago as a result of second domestication. This event truly changed the history of mankind, providing rapid mobility for the first time,” concluded Ludovic Orlando.

This work was mainly supported by the European Research Council (CoG PEGASUS and SyG Horsepower).

“The results obtained significantly complement the overall picture of the domestication of modern horses and make it possible to determine the factors that influenced the beginning of global migrations in the steppe belt of Eurasia in the Late Bronze Age. The territory of Pavlodar Irtysh region and Northern Kazakhstan was an integral part of the processes taking place at that time, the population of which actively participated in them. The materials obtained by the expedition of Toraighyrov University from the settlement of Borly 4 (Lebyazhinsky district of Pavlodar region) supplemented the results of the study of the Botai settlement, allowing us to reasonably identify the Botai type of domesticated horse in the second half of the 4th millennium BC, but its fate remains unclear so far in the 3rd millennium BC Were they immediately abandoned or were they used by the local population in the Asian steppes for some time? Targeted research of the Chalcolithic and Early Bronze Age monuments of Kazakhstan, which is carried out by our university, will allow us to answer these questions. In the meantime, the two recorded lines of development of horses - Botai and Ponto-Caspian - clearly indicate two eras - the Chalcolithic and the Late Bronze Age.” This year, research on all these issues will be continued by our expedition with foreign colleagues from the universities of Exeter, Kiel and others, said Viktor and Ilya Mertz, members of the research team from the Joint Archaeological Research Center named after. A. Kh. Margulan from Toraighyrov University (Pavlodar).

Photo 1: Mounted shepherd catches a horse in Inner Mongolia, China, July 2019. © Ludovic Orlando.

Photo 2: Horse and mule trains carrying heavy loads across the Peruvian Andes, in the Salkantay Mountains, August 2024. © Ludovic Orlando.