Humans’ sense of smell is still evolving

A genetic study shows how smell capabilities were maintained in a hunter-gatherer population

Humans, as an evolutionary group, are often said to be losing their sense of smell. “But our sense of smell is not simply declining,” says Lian Deng of the School of Life Sciences at China’s Fudan University. “It is still being reshaped by lifestyle, diet and even culture.” That’s the upshot of a recent study aimed at revealing how the genetics of human olfaction has changed over the past few millennia.

The study grew from the fieldwork of Hoh Boon-Peng, a geneticist at the IMU University in Malaysia, who saw how important smell still is in the daily life of the region’s hunter-gatherers. They follow their noses to distinguish among herbs, identify ripe fruit and figure out where animals have traveled—they can even tell what kind of animal has passed by based on the smell of its urine—and their language has a strikingly rich vocabulary for odors, Hoh says. Such observations led Deng to ask whether smell’s enduring importance might have left detectable traces in the evolution of smell-receptor genes. In the study, published in Cell Reports , Deng, Hoh and their colleagues analyzed genomes from 50 Indigenous people from the Malay Peninsula and compared them with other populations around the world. The sample included the hunter-gatherers and two other Indigenous groups that focus on farming and agriculture.

The results suggest that the Malay Peninsula hunter-gatherers have preserved a more complete set of smell-receptor genes than the other groups studied. In most populations around the world, many of these genes have accumulated mutations over time that have left about 60 percent of them nonfunctional. But the hunter-gatherers showed significantly fewer mutations in their olfactory-receptor genes. The intact gene variants they carry are linked to sensing earthy, floral and fruity smells—cues often tied to food and other vital resources.

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The genetic differences among the populations did not pertain only to smell. In one of the farming groups, the researchers identified a distinct version of a receptor gene called OR12D3 . Previous studies have linked this gene to insulin secretion , suggesting it may reflect adaptation to the higher-carbohydrate diet that came with agriculture.

Even among modern humans, sense of smell varies widely from person to person, and much of that variation is thought to come from differences in odor-receptor genes, says Duke University molecular geneticist Hiroaki Matsunami, who was not involved in the work. To him, the study provides evidence that humans’ recent evolutionary history might have helped shape these genes.

Deng says hunter-gatherer populations, long underrepresented in genomic research, have allowed the survival of genetic signatures tied to ancient history and have also led to new adaptations. “Such living populations can be invaluable for understanding the deep history of human genetic diversity,” she adds.