New Delhi, Aug. 31: The exclusively male Y chromosome in humans has remained intact over the past six million years, but damaging genetic mutations have struck the Y in chimpanzees, scientists will announce tomorrow.
It’s the price chimps have paid for having multiple sexual partners, and an advantage humans have gained for remaining ' largely ' monogamous, researchers have speculated.
The disparity in the fates of genes on the Y chromosomes of chimps and humans is among surprises thrown up by the first detailed comparison of the genomes of Homo sapiens and Pan troglodytes to be published in the journal Nature.
A research team at the Whitehead Institute at MIT and the Washington University School of Medicine, St. Louis, has shown that the human Y has maintained its count of 27 genes.
The study challenges earlier dire predictions that the chromosome is acquiring mutations and will decay within five to 10 million years.
These same genes in chimps have mutated and become inactive. “The chimpanzee Y has suffered damaging mutations in five of these genes,” said Jennifer Hughes, a scientist at Whitehead.
“So its decay in chimps might have become accelerated in the past six million years since the two species diverged from a common ancestor.”
The researchers said the disparity in the Y may emerge from different mating habits.
“The lost genes are civilian casualties in the war for the fittest sperms,” Hughes told The Telegraph. “It’s a hypothesis now, but it’s the best explanation,” said David Page, who heads a lab at Whitehead.
Mating behaviour affects the number of offspring which, in turn, through evolutionary rules can determine the fate of genes, said human geneticist Partho Mazumdar at the Indian Statistical Institute, Calcutta.