HIV, the only retrovirus that most people have heard of, has caused more than twenty-five million deaths and infected at least twice that number of people since the middle of the twentieth century, when it moved from monkey to man.
It may be hard to understand how organisms from that same family, and constructed with the same genes, could have played a beneficial, and possibly even essential, role in the health and development of any species.
In 1968, Robin Weiss, who is now a professor of viral oncology at University College London, found endogenous retroviruses in the embryos of healthy chickens. When he suggested that they were not only benign but might actually perform a critical function in placental development, molecular biologists laughed.
“When I first submitted my results on a novel ‘endogenous’ envelope, suggesting the existence of an integrated retrovirus in normal embryo cells, the manuscript was roundly rejected,’’ Weiss wrote last year in the journal Retrovirology.
“One reviewer pronounced that my interpretation was impossible.’’ Weiss, who is responsible for much of the basic knowledge about how the AIDS virus interacts with the human immune system, was not deterred.
He was eager to learn whether the chicken retroviruses he had seen were recently acquired infections or inheritances that had been passed down through the centuries. He moved to the Pahang jungle of Malaysia and began living with a group of Orang Asli tribesmen.
Red jungle fowl, an ancestor species of chickens, were plentiful there, and the tribe was skilled at trapping them. After collecting and testing both eggs and blood samples, Weiss was able to identify versions of the same viruses.
Similar tests were soon carried out on other animals. The discovery helped mark the beginning of a new approach to biology.
“If Charles Darwin reappeared today, he might be surprised to learn that humans are descended from viruses as well as from apes,” Weiss wrote.
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>>> Bacaan lanjut yang sangat menarik "Darwin’s Surprise: Why are evolutionary biologists bringing back extinct deadly viruses?" (By: Michael Specter. New Yorker, 3 Dec 2007)