6 Signs Humans Are Still Evolving

When we think of human evolution, our minds wander back to the millions of years it took natural selection to produce modern-day humans. Recent research suggests that, despite modern technology and industrialization, humans continue to evolve. “It is a common misunderstanding that evolution took place a long time ago, and that to understand ourselves we must look back to the hunter-gatherer days of humans,” Dr. Virpi Lummaa, a professor at the University of Turku, told Gizmodo in 2012.

But not only are we still evolving, we’re doing so even faster than before. In the last 10,000 years, the pace of our evolution has sped up, creating more mutations in our genes, and further natural selection from those mutations. Here are some clues that show humans are continuing to evolve.

Humans drink milk.

Historically, the gene that regulated humans’ ability to digest lactose shut down as we were weaned off our mothers’ breast milk. But when we began domesticating cows, sheep, and goats, being able to drink milk became a nutritionally advantageous quality, and people with the genetic mutation that allowed them to digest lactose were better able to propagate their genes.

The gene was first identified in 2002 in a population of northern Europeans that lived between 6000 and 5000 years ago. The genetic mutation for digesting milk is now carried by more than 95 percent of people of northern European descent. In addition, a 2006 study suggests this tolerance for lactose developed again, independently of the European population, 3000 years ago in East Africa.

We’re losing our wisdom teeth.

Our ancestors had much bigger jaws than we do, which helped them chew a tough diet of roots, nuts, and leaves. And what meat they ate they tore apart with their teeth, all of which led to worn-down chompers that needed replacing. Enter the wisdom teeth: A third set of molars is believed to be the evolutionary answer to accommodate our ancestors’ eating habits.

Today, we have utensils to cut our food. Our meals are softer and easier to chew, and our jaws are much smaller, which is why wisdom teeth are often impacted when they come in — there just isn’t room for them. Unlike the appendix, wisdom teeth have become vestigial structures. One estimate says 35 percent of the population is born without wisdom teeth, and some say they may disappear altogether.

We’re resisting infectious diseases.

In 2007, a group of researchers looking for signs of recent evolution identified 1800 genes that have only become prevalent in humans in the last 40,000 years, many of which are devoted to fighting infectious diseases like malaria. More than a dozen new genetic variants for fighting malaria are spreading rapidly among Africans. Another study found that natural selection has favored city-dwellers. Living in cities has produced a genetic variant that allows us to be more resistant to diseases like tuberculosis and leprosy. “This seems to be an elegant example of evolution in action,” Dr. Ian Barnes, a molecular evolutionary biologist at London’s Natural History Museum, said in 2010 statement. “It flags up the importance of a very recent aspect of our evolution as a species, the development of cities as a selective force.”

Our brains are shrinking.

While we may like to believe our big brains make us smarter than the rest of the animal world, our brains have actually been shrinking over the last 30,000 years. The average volume of the human brain has decreased from 1500 cubic centimeters to 1350 cubic centimeters, which is an amount equivalent to the size of a tennis ball.

There are several different conclusions as to why this is: One group of researchers suspects our shrinking brains mean we are in fact getting dumber. Historically, brain size decreased as societies became larger and more complex, suggesting the safety net of modern society negated the correlation between intelligence and survival. But another, more encouraging theory says our brains are shrinking not because we’re getting dumber, but because smaller brains are more efficient. This theory suggests that, as they shrink, our brains are being rewired to work faster but take up less room. There’s also a theory that smaller brains are an evolutionary advantage because they make us less aggressive beings, allowing us to work together to solve problems, rather than tear each other to shreds.

Some of us have blue eyes ...

Originally, we all had brown eyes. But about 10,000 years ago, someone who lived near the Black Sea developed a genetic mutation that turned brown eyes blue. While the reason blue eyes have persisted remains a bit of a mystery, one theory is that they act as a sort of paternity test. “There is strong evolutionary pressure for a man not to invest his paternal resources in another man’s child,” Bruno Laeng, lead author of a 2006 study on the development of blue eyes, told The New York Times. Because it is virtually impossible for two blue-eyed mates to create a brown-eyed baby, our blue-eyed male ancestors may have sought out blue-eyed mates as a way of ensuring fidelity. This would partially explain why, in 2006 recent study, blue-eyed men rated blue-eyed women as more attractive compared to brown-eyed women, whereas women and brown-eyed men expressed no preference.

... And some of us have dry earwax and low body odor.

When you think of earwax, you tend to think of a wet, sticky substance. But not everyone has goopy earwax. A lot of people from East Asia actually have dry, flaky earwax. That texture comes from a mutation to the ABCC11 gene that cropped up somewhere between 30,000 and 20,000 years ago. In addition to creating non-waxy earwax, the mutation also affects a person’s sweat-producing apocrine glands, reducing their body odor.

Read More About Human Evolution:

A version of this story originally ran in 2012; it has been updated for 2024.