Mon, 12 Nov 2012 12:41 CST
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The evolution of the Y chromosome suggests that human history was less polygamous than previously thought. (Australian actor Chris Hemsworth best known for playing Thor in the Marvel movie of the same name.)
San Francisco - The Y chromosome may have gotten a bad rap. Despite the claim that this male sex chromosome is mostly junk, new research suggests it's actually a lean, mean, highly evolved machine for producing the fittest males possible.
The findings, presented Friday (Nov. 9) here at the American Society of Human Genetics' annual meeting, dispute the notion that historically most men in a generation have not passed on their genes while a few lucky guys
fathered hordes of children.
"Averaged over many hundreds of thousands of years, there's likely been a small skew in the number of males to females," said Melissa Wilson Sayres, a researcher at the University of California Berkeley. "There is some skew, but it's not very large."
Fewer alpha males?
Every cell in the human body contains 23 pairs of chromosomes (threadlike structures into which DNA is packed), with one of those pairs comprising the sex chromosomes (an X and Y for males and XX for females). The DNA in the Y chromosome represents about 2 percent of the DNA in human's cells, compared with the X chromosome's 5 percent.
The Y chromosome also has much less variation in its DNA than other types of DNA, meaning that the sex chromosomes in two men will look more alike than other chromosomes do.
Some scientists have argued the Y chromosome
is so uniform because throughout evolution, relatively few men passed on their genes compared with women - in other words, alpha males hogged all the women, while less successful men lost out in the mating game. That would mean that modern-day people have far fewer male ancestors than female ones. But nobody had looked to see if that theory jibed with the genetic makeup of the Y chromosome.