Cattle Domestication: Farmers Continued To Breed Cows With Ancient Wild Ox, New Study Shows

The ancestry of domesticated cattle, or cows, may be a little more complex than previously thought. Roughly 11,000 years ago an extinct wild ox species known as aurochs (Bos primigenius) grazed throughout areas of Europe, Asia and North Africa. When these animals were domesticated, two new species arose through what researchers believed were two separate domestication events that involved wild oxen. These species became known as Bos taurus and Bos indicus. 

Previous research indicated that B. taurus were descendants of western Asian aurochs. However, little was known about how wild European ancestors fit into the picture. In order to find out, University College Dublin researchers extracted DNA from a 6,750-year-old bone that belonged to a wild British aurochs that was excavated from a cave in Derbyshire, England, according to the university's news release.

After sequencing the auroch's complete genome – or genetic blueprint – researchers compared it with the genomes of 81 domesticated B. taurus and B. indicus animals as well as to DNA belonging to over 1,200 modern cows. They discovered evidence suggesting early domesticated cattle continued to be bred with British aurochs, possibly to produce certain desirable traits, researchers suggest.  

"Our results show the ancestors of modern British and Irish breeds share more genetic similarities with this ancient specimen than other European cattle. This suggests that early British farmers may have restocked their domesticated herds with wild aurochs." David MacHugh, senior author on the study from the School of Agriculture and Food Science at University College Dublin, explained in the release. 

This means that some modern domestic cow breeds, including the Scottish Highland and Irish Kerry, have wild ancestors that were both British and Asian, say the researchers. The genetic analysis also revealed that modern cows' neurobiology and muscle development are associated with European ancestors, which suggests that farmers may have bred cattle based on behavioral traits and meat requirements. 

Wild cattle were originally domesticated for a variety of reasons. For one thing, they provided a good source of food that included milk, blood, and meat. For another, their hides were turned into clothing and their hooves and bones were turned into tools. Farmers also used the strong oxen to carry large loads or pull plows. 

"This is the first complete nuclear genome sequence from the extinct Eurasian aurochs. Our new study contradicts earlier simple models of cattle domestication and evolution that we and others proposed based on mitochondrial DNA or Y chromosomes. What now emerges from high-resolution studies of the nuclear genome is a more nuanced picture of crossbreeding and gene flow between domestic cattle and wild aurochs as early European farmers moved into new habitats such as Britain during the Neolithic," MacHugh added. 

The study, recently published in the journal Genome Biology, sheds light on the domestication of cattle and their relationship with wild ancestors. 

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