Humans have been collecting tons of negative mutations in the past few thousand years, a new study suggests.
"Recent human history has profoundly shaped patterns of genetic variation present in contemporary populations," study researcher Joshua Akey, of the University of Washington, told us in an email. "Our results suggest that ~90% of evolutionary deleterious variants arose in the last 200-400 generations."
These mutations are changes in the lettering of our genes, and some of these mutations change the way the proteins made from those genes act. Some can have negative impacts on our ability to survive and reproduce (though often these effects are small) — called deleterious mutations — but others could also be evolutionary fodder for improving the human race.
"Each generation, humanity incurs on the order of 10^11 new mutations," Akey said. "The vast majority of these either have no phenotypic or functional consequences, or are deleterious. However, a small fraction are expected to be advantageous."
"What specific traits they may influence would just be pure speculation, but we can reasonably posit they exist and will be potential substrates for natural selection to act on in the future," Akey wrote.
The study is out this week, Nov. 28, in the journal Nature. The researchers analyzed mutations in the genome of the cellular powerhouse, the mitochondria. They analyzed the genetic material of about 4,000 European-Americans and more than 2,000 African-Americans.
They saw that the parts of this genetic material that hold the instructions for proteins look very different than they would have 5,000 years ago — tons of new mutations have sprung up. This gives our population of humans more options to work with, though many of the mutations could have negative impacts: 86 percent of the negative mutations in European-Americans are less than 5,000 years old.
The dramatic increase in the frequency in which mutations crop up in the population is important in understanding how our modern lives are influencing our evolution — and how the pressures that drive natural selection are changing.
"I do think that the selective forces that act on humans today is probably different than it was a couple of thousand (or hundred) years ago because of advances in medical technology," Akey told us. "However, I strongly disagree with the idea though that humans no longer are subject to any selective forces ... tens of millions of people die every year because of infectious diseases and pathogens are likely still a potent selective force."
Understanding how modern life is changing our evolutionary trajectory will help us get a grasp on the future of the human race. A Stanford researcher recently suggested that our modern lives are making us dumber than our hunter-gatherer ancestors. Akey isn't ready to argue that just yet, but acknowledges it may take time to get rid of some of these negative genetic variants that have sprung up.