Our sense of smell has been crucial for human survival, say Israeli scientists, and continues to be underated.
They have found very few mutations in the genes that code for smell receptors in the nose, suggesting that these genes have been actively preserved by natural selection.
Doron Lancet and colleagues at the Weizmann Institute in Israel studied the thousand-or-so genes that could code for olfactory receptors in the nose. Between 50 and 60 per cent of these genes have accumulated mutations and no longer function. But up to 400 genes have been preserved, implying they were crucial for human survival.
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Lancet thinks the mutations in the active genes have been weeded out by natural selection. 鈥淲e suggest that weak positive selection is responsible for the patterns of genetic variation,鈥� the team writes in the journal Nature Genetics.
Studies of chimpanzee genes have confirmed that this selection process has taken place on human DNA, rather than on the DNA of a distant ancestor.
鈥淭his is very interesting work,鈥� says Tim Jacob of Cardiff University. 鈥淧eople do tend to think that smell isn鈥檛 that vital, and it is very neglected.鈥�
Modern humans probably don鈥檛 use smell in exactly the same way as our ancestors, Jacob says. Today, we don鈥檛 need to detect the scent of a predator, but it remains important to judge whether food is rotten or whether air is breathable. Jacobs thinks that smell may even assist in our choice of mate.
鈥淭ests have found that people prefer the smell of people who are genetically dissimilar to themselves,鈥� Jacob says. 鈥淭hough no one really understands the mechanism of how that might happen.鈥�
There is some evidence that a person鈥檚 major histocompatibility complex (MHC) genes can affect their body odour. Different MHCs indicate different immune systems.
There has also been speculation that people may be able to smell fear. 鈥淗orses and dogs can smell fear on humans,鈥� Jacobs says. 鈥淚f we could smell anxiety on others, it could be useful for raising levels of alertness if you were going with a group into an area of danger, for example.鈥�
Lancet suggests that being able to smell smoke could also boost a person鈥檚 chances of survival.
Humans are not as sensitive to smell as many other mammals, but the sense is still more important than most people realise, Lancet told 快猫短视频. 鈥淎s we鈥檝e become human beings, we have become more oblivious to our nose. We are worse at detecting smells than cats or dogs. But we still use our sense of smell all of the time.鈥�
Source: Nature Genetics (vol 26, p 221)