Wednesday, February 15, 2017

Human Evolution in Action

AKA Anosmia of Androstenone

Humans are not done evolving. The most readily available evidence for this is the vast difference in our abilities to smell. Of the 400 types of olfactory receptors used to code all smellable molecules, humans evidence a sizable difference in the way they use their olfactory switchboard. For example, specific anosmia, or odor-blindness to one particular smell, is very common.

Chances are that one of every two people reading this is anosmic to something. (I would suggest buying the boardgame P.U. The Guessing Game of Smells, sniff through the scented cards, and note which one doesn’t smell bad at all – that’s the one you’re anosmic to.)

In a recent report, scientists are busy decoding these differences in our genetic artifacts using them to chart the distribution of cultural forces on genetic evolution. If you can’t smell androstenone, your OR7D4 gene is turned off. But in the on position, this gene can be coded to “perceive” androstenone as either sweet and floral, or sweaty and urinous.

Androstenone, a derivation of testosterone, is found in humans and especially in male pigs. In fact, to those who find androstenone unpleasant, uncastrated boar meat tastes gross. Many of these people are from Africa. And many of those who can’t smell it at all are from the Northern Hemisphere. Note that the domestication of pigs began in Asia. In a culture where pig is often on the menu, it would not be a good thing for you to smell your dinner as piss and sweat. Over time and across generations, this genetic variant would be deselected.

Here’s another interesting aromatic molecule – isovaleric acid. It is the smell of vomit, sweaty feet, and Parmesan cheese. With no clues given, most people describe it as either disgusting or delicious, and in a totally unpredictable 50/50 distribution. The same people even, at different times, will report different answers.

In this case, it isn’t yet a matter of genetics. Instead, the brain is evolving in real-time, vacillating, feeling, “thinking” about how to perceive this thing.

Follow me here – animal husbandry begins before dairying practices, and after that, cheese-making. There are certain sequences in cultural evolution, and this is one of them. Is it safe to say then, that in some quantity of years, in generations to come, that Parmesan cheese-eating populations will lose their ability to smell isovaleric acid altogether?

Or one day even further in our future, when our cultures have become so far removed from our genetic history, will we stop smelling everything?

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