18 March 2018
Ancient Botai horses fail paternity test for modern domesticated steeds
Published online 28 February 2018
New study debunks two commonly held views about domesticated and wild horse ancestry.
For a long time, it was thought that the Przewalski’s horses, a rare and endangered species, were the last remaining wild horses in the world. Many researchers also believed that Botai horses, the oldest known domesticated horses, were the ancestors of today’s domestic steeds.
But a new study, published in Science, radically challenges previously common knowledge about the ancestry of wild and domesticated horses.
Archaeological evidence and genetic analysis of 88 ancient and modern horses showed that, unlike what is expected, Przewalski’s horses were the direct descendent of Botai horses. Domesticated horses from 4,000 years ago to today share only 2.7% of their genome with that of Botai horses, showing a huge expansion in horse stock since their first domestication.
The study was carried out by an international multidisciplinary team of over 40 scientists, including a researcher from King Saud University, in Saudi Arabia.
The findings suggest that Przewalski’s horses are not really wild; but rather feral—a domesticated animal descent, living in the wild. This means that genuinely wild horses don’t exist anymore.
The study also implies that modern domestic horses have another ancestor.
During the Bronze Age, a huge genomic change has taken place; another population of horses must have replaced Botai horses down the ancestry lane, rendering the true source of horse domestication a mystery. For now, determining the exact ancestor of today’s domestic horses will be a bridge too far; since there are only so many recovered horse genomes from this age.
But scientists are further exploring modern domestic horses’ origin.
“We are sequencing many more early horses from Eastern Europe, Central Asia and other regions to establish where the modern clade of domestic horses came from,“ says Alan Outramof, corresponding author of this study and professor of Archaeology at University of Exeter in the United Kingdom.
- Gaunitz, C. et al. Ancient genomes revisit the ancestry of domestic and Przewalski’s horses. Science https://dx.doi.org/10.1126/science.aao3297 (2018).