Cow's DNA Sequence Reveals Mankind's Influence Over Last 10,000 Years

By David Brown

The genomes of man and dog have been joined in the scientific barnyard by the genome of the cow, an animal that walked beside them on the march to modern civilization.

A team of hundreds of scientists working in more than a dozen countries yesterday published the entire DNA message -- the genome -- of an eight-year-old female Hereford living at an experimental farm in Montana.

Hidden in her roughly 22,000 genes are hints of how natural selection sculpted the bovine body and personality over the last 60 million years, and how man greatly enhanced the job over the last 10,000.

As with other species, genes governing the immune system, the metabolism of nutrients, and social interaction appear to be where much of evolutionary action has occurred. The result is an animal that lives peacefully in herds and grows large on low-quality food, thanks to billions of bacteria it carries around.

Selective breeding has exaggerated and spread some of those traits, producing hyper-passive Holsteins and muscle-bound Belgian Blues, and dozens of humpback Asian breeds that combine characteritics of both.

"Are there signatures of the human hand in the cattle genome? The answer is plainly and clearly yes," said Harris A. Lewin, head of the Institute for Genomic Biology at the University of Illinois at Urbana-Champaign. He is the author of one of three papers on the cow genome appearing in the journal Science.

Although sheep and goats were domesticated earlier, cattle are the most important herd animals in the world. There are about 800 distinct breeds, and together they contribute to the nutrition or income of about 6.6 billion people.

The cow genome is the first of a livestock animal to be sequenced. It is part of the effort to read and analyze the DNA of organisms of scientific, medical or economic importance to human beings. In addition to dozens of microbes and several plants, they include the chimpanzee, mouse, dog, chicken, mosquito, fruit fly and platypus.

The cow data is already proving useful.

The location on the cow's 31 chromosomes of the recently changing genes is giving scientists a much better insight about molecular events that help drive evolution and create new species. On a purely practical level, the genome is allowing farmers to select animals to breed based on their genetic endowment rather than on the more laborious examination of their pedigree.