What if we had family trees…for cows?
A genetic study of Longhorn and related breeds tells a fascinating global history of human and cattle migration.
To reconstruct the genetic history of Texas Longhorns, BEACONites Emily Jane McTavish and her advisor David Hillis at the University of Texas at Austin, along with colleagues from the University of Missouri-Columbia, analyzed almost 50,000 ‘genetic markers’ from 58 cattle breeds.
“It was known on some level that Longhorns are descendants from cattle brought over by early Spanish settlers, but they look so different from the cattle you see in Spain and Portugal today. So there was speculation that there had been interbreeding with later imports from Europe. But their genetic signature is completely consistent with being direct descendants of the cattle Columbus brought over,” said Hillis, the Alfred W. Roark Centennial Professor in the College of Natural Sciences at University of Texas at Austin.
Emily Jane McTavish, a doctoral student in the lab of biology professor David Hillis, is shown here, with Longhorns, at Hillis’s Double Helix Ranch. Photo by Liz Milano.
The study reveals that approximately 85 percent of the Longhorn genome is “taurine,” or from domesticated wild aurochs in the Middle East around 8,000-10,000 years ago. The remaining 15 percent is “indicine,” or from aurochs originally domesticated in India. As a result, Longhorns look more similar to purer taurine breeds such as Holstein, Hereford and Angus, which came to Europe from the Middle East, than they do to indicine cattle, which often have a characteristic hump at the back of the neck.
The Texas Longhorn breed are direct descendants of the first cattle in the New World brought over by Columbus and to the rest of the continent through later Spanish colonists, the paper suggests. As the Spanish moved northward into Texas at the end of the 17th century, the cattle escaped or were turned loose on the open range, where they remained mostly wild until being rounded up for beef after the Civil War. During this time, under the pressures of natural selection, Longhorns were selected for survival traits that had been artificially bred out of their European ancestors, such as longer horns for defense and better heat and drought tolerance. Their hybrid ancestry likely contributed important genetic variation for selection to act on.
“Living wild on the range, [Longhorns] had to become very self-sufficient. Having that genetic reservoir from those wild ancestors, made it possible for a lot of those traits to be selected for once again,” said McTavish. As the Earth warms, these genes may prove valuable to ranchers looking to breed the Longhorns’ toughness into other breeds of cattle.
So, in the face of global change, we can rest assured knowing that these hearty cows have taken a long journey and that their family history will live on.
Read more here: Emily Jane McTavish, Jared E. Decker, Robert D. Schnabel, Jeremy F. Taylor, and David M. Hillis New World cattle show ancestry from multiple independent domestication events PNAS 2013 : 1303367110v1-201303367.
[This is a reposted excerpt from my work in the BEACON Buzz]