Lost DNA May Have Made Us More Human

The vanished snippets of genetic code may account for human's large brains, spineless penis, researchers say

WEDNESDAY, March 9 (HealthDay News) -- What difference does it make if homo sapiens lost a snippet of DNA over the millennia? A lot, as it turns out.

Losing a few snippets of DNA may explain why parts of our brains work differently than those of other mammals. It may also be the reason that male penises are not spiny, as are those of some other animals, including chimpanzees and mice.

It appears that a genetic trait for a spiny penis vanished more than 500,000 years ago, according to the study, published March 10 in the journal Nature. Scientists also think the loss of bits of DNA may explain why some parts of our brains are bigger than those in other animals.

"It's not only unusual, but also particularly interesting, to find these sequences missing in humans," said study co-senior author David Kingsley, a professor of developmental biology at Stanford University, in a university news release. "These are the same type of molecular events that have been shown to produce evolutionary differences among other organisms."

The study authors reached their conclusions after examining genomes to find 510 regions that aren't found in humans but are in chimpanzees and other mammals.

"We basically asked where evolution favored tweaking gene expression to get human-specific traits," said study co-senior author Gill Bejerano, Stanford assistant professor of developmental biology and of computer science, in the news release. "We found two main categories of enrichment: genes involved in receptor signaling for steroid hormones like testosterone, and genes involved in neural development in the brain."

More information

For more on DNA, visit the U.S. National Library of Medicine.

Randy Dotinga SOURCE: Stanford University, news release, March 9, 2011

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