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?

On Sweetness and Flowers

finedininglovers.com

"French scientists identified a gene that's far more active in a heavily scented kind of rose than in a type with little odor. This gene, which produces an enzyme, revealed the odor-producing process."

AKA "Biosynthesis of monoterpene scent compounds in roses"

Roses have not been designed over centuries of human endeavor to smell good, but to look good. Roses may have been initially valued for their heavenly scent, but over time, they have been selected for reasons of visual beauty.

A selection from Hidden Scents:

Crossing as often as it does with the Food Industry, Fragrance is often interpreted to the mind as taste. “Sweet” is frequently used as an olfactory descriptor. However, calling caramel-smell Sweet is not a chemical consequence of the molecule, but an effect of memory. If sucrose is paired with an odor, any odor, it will eventually “smell sweet”. The potential effect on odor perception that is cued by such multi-sensory information is thought to be the minimization of “perceptual dissonance between the dominant sense (vision) and the minor sense” (Wilson & Stevenson 2006).

Smells are not just Sweet; Castoreum is Umami, and Body Odor, Sour. Yet something about the word, the taste, and the smell of “Sweet” is linked together, and can be evidenced in the fact that the word “sweet” is the most commonly used sub-category heading in the Aldrich catalog (2013), which is a chemical clearinghouse for Flavor and Fragrance scientists. The biases and idiosyncrasies inherent in the Aldrich Catalog as a universal aroma reference are immediate and comprehensive. The catalog is a flavor tool, first of all, and as a commercially-driven pursuit flavor reigns supreme over fragrance alone. The fact that “Sweet” as a sub-category has the most centrality (it falls under Balsamic, Woody, Fruity and Minty) could relate to a confluence of the pervasive availability of sweet aromas, or the sweet-tooth of a certain society, or that there really is something sensually similar about the relative phenomena. Unresolved in that matter, we can scrape-together at least that the description of a smell will tend to be communicated via other, more intentionally-simulable channels of association – anything but the olfactory-specific semantic network of experience, because of course, such a thing is so halting and reluctant in its cooperation, if at all.

In parallel to this gustatory congruency of Sweetness, it is a curious thing to consider: are Florals such an extensive part of the perfumer’s repertoire because of their associated visual aesthetic beauty? David Howes responds in telling of his work with the Papa New Guinean Kwoma people (Howes 2002:76). He presents plastic cards impregnated with scent, and painted with a corresponding color (cinnamon is brown, coconut is white, etc.). When surveyed on the most-liked odor, respondents voted Rose in the vast majority. After having hidden the red-colored Rose scent in an envelope, however, the overwhelming preference disappeared (along with Howes’ search for a universal aroma preference, à la Berlin and Kay, 1969).

Notes:

Berlin B & Kay P (1969). Basic Color Terms: Their Universality and Evolution. Berkeley: University of California Press.

Howes D (2002). Nose-wise: Olfactory Metaphors in Mind. In: Olfaction, Taste, and Cognition, ed. C Rouby, B Schaal, D Dubois, R Gervais, & A Holley, pp. 67-81. Cambridge, U.K: Cambridge University Press.

Sigma-Aldrich (2013). Aldrich Chemistry 2012-2014: Handbook of Fine Chemicals. Sigma-Aldrich.

Wilson D A, Stevenson R J (2006). Learning to Smell: Olfactory Perception from Neurobiology to Behavior. Baltimore: Johns Hopkins University Press.