March 26, 2013
The Genetic History Of The Texas Longhorn
April Flowers for redOrbit.com - Your Universe Online
The Texas Longhorn is an iconic species. Just the thought of one brings to mind all things Texas, but new research from the University of Texas at Austin reveals that the cattle have a hybrid global ancestry.
A fascinating story of the global history of human and cattle migration is told in the genome of the Longhorn and related breeds. This history traces back through Christopher Columbus' second voyage to the New World, the invasion of Spain by the Moors and the ancient domestication of the aurochs in the Middle East and India.
"It's a real Texas story, an American story," said Emily Jane McTavish, a doctoral student in the lab of biology professor David Hillis. "For a long time people thought these New World cattle were domesticated from a pure European lineage. But it turns out they have a more complex, more hybrid, more global ancestry, and there's evidence that this genetic diversity is partially responsible for their greater resilience to harsh climatic conditions."
The UT research team collaborated with colleagues from the University of Missouri-Columbia to reconstruct the genetic history of Texas Longhorns by analyzing almost 50,000 genetic markers from 58 cattle breeds. The research, the most comprehensive analysis to date, was funded in part by the Cattlemen's Texas Longhorn Conservancy. The Conservancy helped the scientific team gain access to samples used by ranchers.
The study shows that the Longhorn is a direct descendant of the first cattle present in the New World. Columbus imported the original cattle to Hispaniola in 1492. Spanish colonist's ships brought them to the continent in 1521. For the next two hundred years, the Spanish slowly moved the cattle north, finally arriving in what would become Texas near the end of the 17th century. After escaping or being turned loose on the open range, the cattle remained mostly wild for the next two centuries.
[ Watch the Video: The Global History of the Texas Longhorn ]
"It was known on some level that Longhorns are descendants from cattle brought over by early Spanish settlers," said Hillis, the Alfred W. Roark Centennial Professor in the College of Natural Sciences, "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."
Being a "pure" descendant of the ancestral cattle from the Iberian peninsula, the Longhorn has a more complicated ancestry than scientists originally understood. The study revealed that about 85 percent of the Longhorn genome is "taurine," which means they are descended from the wild aurochs that were domesticated in the Middle East 8,000 — 10,000 years ago. Because of this, Longhorns have a very similar look to purer taurine breeds such as Holstein, Hereford and Angus, which came to Europe from the Middle East.
The remaining 15 percent of the Longhorn genome is "indicine" as a result of a second domestication of the ancient aurochs in India. The indicine cattle, which often have a characteristic hump at the back of the neck, migrated into Africa and into the Iberian peninsula.
"It's consistent with the Moorish invasions from the 8th to the 13th centuries," said Hillis. "The Moors brought cattle with them, and brought these African genes, and of course the European cattle were there as well. All those influences come together in the cattle of the Iberian peninsula, which were used to stock the Canary Islands, which are where Columbus stopped and picked up cattle on his second voyage and brought them to the New World."
Most of the cattle eventually went feral after being brought to the New World. The pressures of natural selection forced the Longhorn to re-evolve ancient survival traits that had been bred out of their European ancestors. For example, they were able to defend against predators with the selection for longer horns. They developed into a hardy species, leaner and more able to survive heat and drought.
"The Longhorns that were in the area when Anglo settlers arrived almost looked more like the ancestral aurochsen than like modern cattle breeds," said McTavish. "Living wild on the range, they 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."
Specifically, the indicine heritage probably helped as the climate in Africa and India is generally drier and warmer than the European climate.
Until after the Civil War, the Longhorns remained wild on the range or very loosely managed. Texans rounded up the wild herds and began to supply beef to the rest of the country. The popularity and fortunes of the Longhorn have waxed and waned with the changing needs of American consumers.
"The Longhorns almost went extinct starting in the late 19th century," said Hillis. "A lot of the value of cattle at that time had to do with the fat they had, because the primary lighting source people had was candles, made of tallow, and Texas Longhorns have very low fat content. Ranchers began fencing off the range and importing breeds from Europe that had higher fat content. That's when Americans began developing their taste for fatty beef, so then the other cattle became valuable in that respect as well. The only reason the Longhorns didn't go extinct was because half a dozen or so ranchers kept herds going even though they knew that these other breeds were more valuable in some sense. They appreciated that the Longhorns were hardier, more self-sufficient."
Hillis raises a Longhorn herd of his own at the Double Helix ranch. He said that the winds of history are currently blowing in the Longhorns' direction because they can survive in hotter, drier climates. As the world temperatures rise due to global warming, this becomes an important trait for a species to have. The Longhorn also provides lean and grass-fed beef, which is viewed as healthier by consumers. Ranchers may find the Longhorn genes valuable. Increasingly sophisticated information allows the ranchers to selectively breed Longhorn toughness into other breeds of cattle.
"It's another chapter in the story of a breed that is part of the history of Texas," he said.
Results of this study were published in Proceedings of the National Academy of Sciences.