How Farming Changed The Human Nose, According To DNA

Your Ancestors’ Diet May Have Changed How Well You Can Smell

Somewhere in the rainforests of Peninsular Malaysia, the Negrito people have been hunting and foraging for thousands of years, relying on their senses to find food, avoid danger, and read the land around them. Now a genetic study suggests that way of life may have left a mark on their DNA, specifically in the genes that govern what they can smell. Research published in Cell Reports found that Negrito hunter-gatherers carry fewer mutations likely to disrupt smell gene function compared to neighboring farming communities, and that their smell genes show patterns consistent with natural selection working to preserve them over time. The researchers caution that genetic drift and demographic history cannot be fully ruled out as contributing factors.

What the study reveals is that how people make a living, hunting and foraging versus farming, can leave a measurable imprint on the human genome, right down to the genes shaping what odors a person can detect.

How Smell Genes Differ Between Hunter-Gatherers and Farmers

The study centered on the Orang Asli, the indigenous peoples of Peninsular Malaysia. These groups share a general geographic region but differ sharply in lifestyle. The Negritos, scattered in isolated areas of the north, are traditional hunter-gatherers who rely on forest resources. The Senoi, in the central region, practice shifting agriculture supplemented by foraging. The Jakun, in the south, are more settled farmers. That range of lifestyles, all based near tropical rainforest, gave scientists a natural laboratory to test whether cultural practices can drive genetic change in sensory biology.

Researchers analyzed genetic data from 50 Orang Asli individuals across these three groups, alongside data from more than 2,800 people drawn from 65 populations worldwide. They focused on a large family of genes responsible for producing the proteins in the nose that detect specific odor molecules. Humans carry roughly 800 of these genes, though about 60% have become nonfunctional over evolutionary time, a pattern scientists often attribute to humans becoming more reliant on vision than smell.

Globally, smell genes harbor significantly more mutations than comparable regions of the genome. Negrito hunter-gatherers bucked that trend. Their smell genes carried fewer mutations likely to disrupt gene function than those of other Southeast Asian populations. Statistical tests showed their smell gene patterns deviated from what would be expected if evolution were acting randomly, a result consistent with natural selection tending to preserve gene function, though the authors note demographic history remains a plausible alternative explanation.

Ancient Smell Genes Tied to Rainforest Survival

When researchers mapped which genes were most genetically distinct across the three Orang Asli groups, the Negritos stood out for genes tied to detecting musk, acidic, and cheesy smells, odor categories with potential relevance to tracking animals and evaluating food. One gene, OR12D2, showed a strong signal that a beneficial variant had spread rapidly through the population. This gene is associated with detecting earthy and musty odors like geosmin, the compound responsible for the smell of rain-soaked soil. Geosmin is widespread in tropical rainforest environments, and the researchers suggest that selection on genes involved in detecting it “may contribute to the Negritos’ ability to navigate their environment, locate resources, and forage for edibles such as mushrooms.”

Critically, the favored version of OR12D2 in the Negritos was not a new mutation. It was the older, ancestral form. Analysis of ancient genomes showed this version declined in frequency across South and East Asian populations over the past 10,000 years, tracking closely with the spread of agriculture, while holding steady or increasing in populations where hunter-gatherer lifestyles persisted longer.

Another gene cluster under apparent selection in the Negritos, OR52J3 and OR52E2, is associated with detecting buttery and sweet smells, the kind of scent that may signal high-fat, calorie-dense food. Research has shown that humans can distinguish milk samples of different fat concentrations by smell alone, suggesting an evolved sensitivity to energy-rich foods. The ancestral version of this cluster dates back an estimated 284,500 years, predating modern humans’ migration out of Africa.

Farming Pushed Smell Genes in a Different Direction

Agricultural populations told a different story. The Jakun showed genetic changes in smell genes linked not just to odor detection but to broader functions like insulin regulation, lung function, and immune response. This overlap exists because some genes serve double duty. One example, OR12D3, has been shown to act as a receptor for a form of insulin and to influence how the body manages insulin secretion. Farming populations that eat carbohydrate-heavy diets face repeated blood sugar spikes, potentially favoring changes in genes involved in glucose regulation, even when those same genes also function as smell receptors.

A Trace of Neanderthal in the Mix

Perhaps the most unexpected finding involved genetic material inherited from Neanderthals. In one specific stretch of chromosome 11, researchers found a cluster of Neanderthal-origin DNA present at notable frequency in the Bateq Negritos, a region containing genes for detecting musk and floral-fruity scents. Five Bateq gene sequences closely resembled those of a Neanderthal specimen from Siberia. These ancient variants are associated with reduced sensitivity to musk but greater sensitivity to a compound found in floral and fruity scents. The researchers tentatively suggest this may represent adaptive introgression, while noting that the precise selective pressures behind it remain unclear.

Culture and genetics are not separate forces in human evolution. For the Negrito people of Malaysia, a community that has sustained its way of life for thousands of years in some of the world’s most biodiverse forests, the genetic record of that survival is still visible in the very genes that help them smell it.

---