Why it’s so hard to unravel the mysterious origins of domestic horses

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Scientists – and horse owners – often wonder how exactly horses were domesticated. Photo: Infomaster / Flickr, CC BY-SA

Many questions remain about the domestication of horses, writes Jan Hoole, lecturer in biology at Keele University In England.

There is still a lot we don’t know about how and where horses were first domesticated. Experts have long believed that all modern horses probably descended from a group of animals belonging to the Botai culture, which flourished in Kazakhstan about 5,500 years ago.

But now, a new study published in Science suggests that Botai horses were not the ancestors of our modern equine companions – and questions what we thought we knew about one of the only species of “wild” horses today: Przewalski’s horse.

There are now very few, if any, truly wild horse species that have never been domesticated. Scientists know that Przewalski’s horse is not an ancestor modern domestic horses, since studies were carried out on equine mitochondrial DNA in 2002. But it now seems that far from being the last vestiges of a truly wild horse species, Przewalski’s horse is the wild descendant of the domesticated Botai horses.

The study's authors imagine what Przewalski's ancient ancestors would have looked like.  Image: Ludovic Orlando, Seas Goddard, Alan Outram, CC BY
The study’s authors imagine what Przewalski’s ancient ancestors would have looked like. Image: Ludovic Orlando, Seas Goddard, Alan Outram, CC BY 4.0

Let’s take a look at the science.

Born wild?

Directed by Charleen gaunitz from the Danish Museum of Natural History, the 47 study authors sequenced the genomes of 42 ancient horses from Kazakhstan and various sites in Eurasia, and compared them to published data from 46 ancient and modern horses.

Their analysis showed that Przewalski’s horse and the oldest horses in Eurasia were not genetically similar, as one would expect. In fact, Przewalski’s horse was found to be most closely related to Botai horses, while all modern domesticated horses belong to a separate group. If that’s true, it upsets what we thought we knew about wild and domestic horses.

But one of the difficulties in drawing conclusions from the DNA of a modern Przewalski horse is that the species suffered a massive decline in the first half of the 20th century. The last seen in the wild has been spotted back to the 60s, and it has been declared extinct in the wild. A captive breeding program has started, and all today’s Przewalski horses trace their ancestry to 13 individuals, who were in zoos around the world at the time. Equus ferus przewalskii was reintroduced to nature at the end of the 20th century.

Back in their place: Przewalski's horses in the Mongolian wilderness.  Photo: gsz / Flickr, CC BY-NC-ND
Back in their place: Przewalski’s horses in the Mongolian wilderness. Photo: gsz / Flickr, CC BY-NC-ND

Gaunitz and his colleagues suggest that there has been a considerable invasion of modern horse genes into the species. But the team was fortunate to have DNA from a specimen dating back to the 19th century, before the population collapsed. This allowed them to show that the Botai horses were the direct ancestors of another breed of horse from the early Bronze Age called Borly4, and that these Borly4 horses were the direct ancestors of the pre-collapse Przewalski horse.

What nose?  RPatts / Flickr, CC BY-NC-ND
What nose? Photo: RPatts / Flickr, CC BY-NC-ND

Unsolved mysteries

This leaves the origins of modern horses shrouded in mystery. It appears that they are descended from a completely different group of horses, but genomic analysis suggests that they were successful in interbreeding with Botai horses to a small extent as the population spread across the landmass. The study’s authors suggest that Hungary, in Eastern Europe, may be one of the many places where modern horse ancestors were first domesticated, as the oldest horse remains have been found there. been recovered.

Previous studies have suggested Iberia, North Africa and Eurasia as possible sites of domestication. And it seems likely that horses – like dogs – have been domesticated independently in a number of different places and over a long period of time.

Scientists – and horse owners – often wonder how exactly horses were domesticated. It has been suggested that they were originally prey animals that humans began to protect and reproduce to ensure a constant supply of meat. Over time, their keepers began to use them for milk, hides, and transportation. Alternatively, they may have been deliberately placed under human control to help hunt herds of wild horses.

Catch us if you can.  Photo: Brian395 / Flickr, CC BY
Catch us if you can. Photo: Brian395 / Flickr, CC BY

Regardless of the method, it now seems likely that the very hardy horses of the Botai were not the ultimate ancestors of the delicate modern thoroughbred racehorse, nor the heavy draft horses that were the core workforce. of agriculture in many parts of the world until the beginning. of the 20th century.The conversation

The genes of the Botai horse are only preserved in the small and precarious populations of the Przewalski horse, which struggle to survive in the regions of the Gobi desert and the mountainous steppe regions of Mongolia where they have been reintroduced. All the more reason then, to continue to ensure the survival of this species – perhaps the last repository of the horse’s ancient DNA.

Jan Hoole, lecturer in biology, Keele University
This article originally appeared on The Conversation. Read the original article.


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