Changes in human diets are so powerful that they can shape the way we look. In fact, the shift from hunting and gathering to agriculture may have transformed the shape of our heads, according to a recent study from the University of California, Davis.
For six months, David Katz — now a postdoctoral fellow at the University of Calgary — traveled the world to measure approximately 1,000 mandible and cranium samples from ancient hunter-gatherers and agriculturalists. He studied specimens from museums in San Jose, Philadelphia, Vienna, Paris, Copenhagen, Tokyo, and Hanoi — all while carrying his digitizer, a tool that allowed him to painstakingly measure each one and create a high-dimensional data set.
“Once that’s done, it’s all computer code,” he said.
Katz and his colleagues found that humans from farming communities had slightly smaller skulls and jaws than hunter-gatherers, and the difference was most noticeable among those who ate higher amounts of dairy. It makes sense, since a glass of milk or a glob of cheese is easier to chew.
“Probably, the fact that our diets today are so much softer [than before] is one of the reasons that people need to get their wisdom teeth taken out,” he said. “We don’t stimulate bone growth enough to create enough space in the jaw for that third molar, ultimately.”
Scientists have been looking for links between diet and human morphology for decades, Katz said, but this is the first time anyone has looked at skull morphology across so many different populations.
“What we’ve been able to do is look at what the worldwide relationship of diet and skull or mandible shape is, and that’s accounting for genetic relationships,” Katz said. “It all suggests that humans continued to evolve to some extent, even after we became Homo sapiens. Evolution does not stop at the origins of modern humans.”
In other words, a critical lifestyle shift thousands of years ago might have influenced what we see in the mirror today.
“When you look around the world, you see that people differ quite dramatically. And the old-fashioned way to look at it would be looking at racial differences,” said Robert Franciscus, a professor of anthropology at the University of Iowa. “So this idea that these changes in how we look may be related to shifting patterns in our eating — it’s an utterly fascinating question.”
That being said, it’s not as though an ancient love for cheese or gardening led to jaw-dropping changes between people around the world.
“Human populations, regardless of diet, climate, and evolutionary history, still tend to be very similar to each other,” Katz said. “When we talk about how different humans are around the world from each other, the cranium says we’re not all that different.”
Kelly Kasulis, a freelance journalist, is a frequent Ideas contributor. Follow her on Twitter @KasulisK.