At the mercy of natural selection since the dawn of life, our ancestors adapted, mated and died, passing on tiny genetic mutations that eventually made humans what we are today.
But evolution isn't bound strictly to genes anymore, a new study suggests. Instead, human culture may be driving evolution faster than genetic mutations can work.
In this conception, evolution no longer requires genetic mutations that confer a survival advantage being passed on and becoming widespread. Instead, learned behaviors passed on through culture are the "mutations" that provide survival advantages.
This so-called cultural evolution may now shape humanity's fate more strongly than natural selection, the researchers argue.
"When a virus attacks a species, it typically becomes immune to that virus through genetic evolution," study co-author Zach Wood, a postdoctoral researcher in the School of Biology and Ecology at the University of Maine, told Live Science.
Such evolution works slowly, as those who are more susceptible die off and only those who survive pass on their genes.
But nowadays, humans mostly don't need to adapt to such threats genetically. Instead, we adapt by developing vaccines and other medical interventions, which are not the results of one person's work but rather of many people building on the accumulated "mutations" of cultural knowledge.
By developing vaccines, human culture improves its collective "immune system," said study co-author Tim Waring, an associate professor of social-ecological systems modeling at the University of Maine.
And sometimes, cultural evolution can lead to genetic evolution. "The classic example is lactose tolerance," Waring told Live Science. "Drinking cow's milk began as a cultural trait that then drove the [genetic] evolution of a group of humans."
In that case, cultural change preceded genetic change, not the other way around.
The concept of cultural evolution began with the father of evolution himself, Waring said. Charles Darwin understood that behaviors could evolve and be passed to offspring just as physical traits are, but scientists in his day believed that changes in behaviors were inherited. For example, if a mother had a trait that inclined her to teach a daughter to forage for food, she would pass on this inherited trait to her daughter. In turn, her daughter might be more likely to survive, and as a result, that trait would become more common in the population.
Waring and Wood argue in their new study, published June 2 in the journal Proceedings of the Royal Society B, that at some point in human history, culture began to wrest evolutionary control from our DNA. And now, they say, cultural change is allowing us to evolve in ways biological change alone could not.
Here's why: Culture is group-oriented, and people in those groups talk to, learn from and imitate one another. These group behaviors allow people to pass on adaptations they learned through culture faster than genes can transmit similar survival benefits.
An individual can learn skills and information from a nearly unlimited number of people in a small amount of time and, in turn, spread that information to many others. And the more people available to learn from, the better. Large groups solve problems faster than smaller groups, and intergroup competition stimulates adaptations that might help those groups survive.
As ideas spread, cultures develop new traits.
In contrast, a person only inherits genetic information from two parents and racks up relatively few random mutations in their eggs or sperm, which takes about 20 years to be passed on to their small handful of children. That's just a much slower pace of change.
"This theory has been a long time coming," said Paul Smaldino, an associate professor of cognitive and information sciences at the University of California, Merced who was not affiliated with this study. "People have been working for a long time to describe how evolutionary biology interacts with culture."
It's possible, the researchers suggest, that the appearance of human culture represents a key evolutionary milestone.
"Their big argument is that culture is the next evolutionary transition state," Smaldino told Live Science.
Throughout the history of life, key transition states have had huge effects on the pace and direction of evolution. The evolution of cells with DNA was a big transitional state, and then when larger cells with organelles and complex internal structures arrived, it changed the game again. Cells coalescing into plants and animals was another big sea change, as was the evolution of sex, the transition to life on land and so on.
Each of these events changed the way evolution acted, and now humans might be in the midst of yet another evolutionary transformation. We might still evolve genetically, but that may not control human survival very much anymore.
"In the very long term, we suggest that humans are evolving from individual genetic organisms to cultural groups which function as superorganisms, similar to ant colonies and beehives," Waring said in a statement.
But genetics drives bee colonies, while the human superorganism will exist in a category all its own. What that superorganism looks like in the distant future is unclear, but it will likely take a village to figure it out.