Scientists say farming reshaped the human nose — and our sense of smell hasn’t been the same since
Scientists believe the reason is the shift from humans' dependence on smell to vision
A new study across three Malaysian indigenous groups with different lifestyles has uncovered a surprising phenomenon. When researchers (Yuenyang Ma, Book-Peng Hoh, Shuhua Xu, and Lian Deng) studied the distinctive lifestyles of 50 individuals from the Orang Asli, they found that the sense of smell (olfaction) is heavily influenced by how they live, particularly how they gather their food (hunting and foraging vs. farming). The research is published in the National Library of Medicine.
The subjects belonged to three communities, namely Negritos, Senoi, and the Jakun. These groups reside in the same broader region, but they have polar opposite lifestyles. While Negritos are traditional hunter-gatherers who depend on forest resources for survival, the Jakun in the south are settled farmers, and the Senoi are somewhere in the middle. It means they not only practice shifting agriculture; they also extract food from the wild.
Considering the differences, the study analyzed the protein-producing genes (in the nose) responsible for detecting smell. Humans carry around 800 smell-related genes, but nearly 60% are no longer functional due to evolution. A report by StudyFinds states that scientists believe the reason is the shift from humans' dependence on smell to vision.
Researchers observed that the hunter-gatherer group (the Negrito) carried fewer harmful mutations that could disrupt gene function. Moreover, they found that the group that primarily survived on forest produce had more functional smell-related genes than other groups. This variation is surprisingly not random. In fact, researchers believe natural selection may be involved, resulting in the phenomenon. It means their environment and habits may have helped them sustain their strong-smelling ability over time.
The Negritos were also found to have genes to detect distinctive smells, such as musky, acidic, and cheesy. Now, this ability is useful for tracking animals and judging whether a food is safe to consume. But the real question is whether the researchers are sure that natural selection is responsible for such genetic differences.
Yes, but how are they so certain? Well, OR12D2, an important gene, showed a strong link between the two. The olfactory receptor gene helps our nose detect specific smells, such as Geosmin, which is typical in tropical rainforest environments. Now, the favored gene in the Negritos was not a new mutation and is the same version humans carried long ago. Notably, this ancient version became less common in populations over time, and more and more people shifted to farming instead of traditional hunting and gathering to survive.
"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," the report added. However, the case was totally different when scientists examined the other two groups. The Jakun in the southern regions showed genetic changes in smell-related genes. In fact, it not only influenced their smell but also other functions such as insulin control, lung function, and immune response. "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," the report mentioned.
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