Interesting indeed. We need all the help we can get!
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The findings represent the latest in a series of landmark efforts to use the human genome, which was decoded in 2003, to understand human biology and unravel the mysteries of evolution.
The findings support the notion that the planet's exploding population is a living laboratory for genetic trial and error, researchers say. By tracking the changes over time, the researchers found clear evidence that we're not who we used to be.
Many of these changes were forced on early humans by changing conditions, including waves of infectious diseases, the shift to an agricultural diet and migrations to colder climates. Some are still unexplained.
For instance, just 10,000 years ago — the blink of an eye in evolutionary time — fewer people carried the gene for an enzyme called lactase, which allows humans to digest cow's milk. A bigger proportion of people had the dark skin of our African ancestors, and no one had blue eyes.
"Blue eyes are new," says lead author John Hawks of the University of Wisconsin.
Hawks says the findings, in today's Proceedings of the National Academy of Sciences, are merely "breaking the ice" in a rapidly expanding effort to use genetics to explain how people have changed since the first humanlike creatures appeared 7 million years ago.
"It's a very important paper," says Clark Larsen, chairman of anthropology at Ohio State University. He says his own study of physical evidence supports the researchers' notion that there was "a ton" of biological change in the past 10,000 years. "Ten thousand years is a tiny part of the picture of human evolution," he says. "It's still going on. Right before our eyes."
Some evolving traits are simple to track. Blue eyes today are common, and millions of people in northern climates now carry the lactase gene, along with about half of those living along the Mediterranean. Why did the lactase gene spread so rapidly? Because it helps people survive and bear children, says co-author Henry Harpending of the University of Utah.
"If you can metabolize milk sugar rapidly, it gives you an advantage when food is scarce," he says.
People who survive are more likely to pass a gene along to their offspring, who also are better able to survive and reproduce. But inheriting a gene doesn't always confer an advantage, Harpending says.
The gene for sickle cell anemia offers an advantage to people living in equatorial Africa, because it helps guard against malaria.
Outside Africa, it's a different story. If a child inherits two copies, one from each parent, the blessing can become a deadly scourge. "In the U.S., where there's no malaria, there are at least 70,000 people leading impaired lives," Harpending says.
Other genetic changes have taken root in the genome, though they don't have any obvious influence on survival or reproduction. "What do people with blue eyes have that made them have more children?" Hawks asks. "I dunno."