Nature’s Blueprint: Why We Haven’t Stopped Evolving

In the morning, a technician in Harvard’s ancient DNA lab drills into a fragment of bone, and a fine white powder falls into a vial material that once belonged to someone who lived thousands of years ago. In that dust, scientists are finding something unexpectedly current.

In a vast study published on Wednesday in the journal Nature, from examining DNA from 15,836 ancient human remains, scientists found 479 genetic variants that appeared to have been favored by natural selection–the fundamental biological process where organisms better adapted to their environment tend to survive and produce more offspring, just in the past 10,000 years. “There are so many of them that it’s hard to wrap one’s mind around them,” said David Reich, a geneticist at Harvard Medical School and an author of the new study (New York Times).

These findings indicate that evolution is not just a story of the past. Instead, human genes have continued to shift in response to changing environments. Some of the genetic changes are linked to traits seen in people today. In some cases, traits that were once helpful for survival may now be connected to modern health conditions.

The study also raises new questions. For example, the researchers found that genetic variants that raise the odds of a smoking habit have been getting steadily rarer in Europe for the past 10,000 years. Something is working against those variants, but it can’t be the harm from smoking. Europeans have been smoking tobacco for only about 460 years, hints that the forces of natural selection can be complex and surprising. “My short answer is, I don’t know,” said Ali Akbari, a senior staff scientist at Harvard and an author of the study. The scientists can’t see from their research so far what forces might be making these variants more or less common.

Overall, the research highlights that humans are still evolving, even in a world shaped by technology and modern lifestyles. Nature, it seems, continues to leave its mark, one gene at a time.