Editor’s note: My apologies to anyone who read this article between the day I first posted it and February 13. I wrote it at the end of a couple cracked out sleepless days, and my ability to produce and discern quality writing was vastly inhibited.
I am currently reading the text Food preferences and taste: continuity and change by Helen M. Macbeth. It comprises all of the papers presented at a European conference on tastes and foods from 1997. The conference covered a range of topics–from the history of the potato to the glucose sensitivity of great apes–and I’m finding it a fascinating read. More than that, too, I’m looking forward to engaging follow up studies from the interesting questions they raise.
I just finished the section on taste sensitivity. What I learned is that cultures vary in taste sensitivity depending on their nutritional needs. Some taste sensitivities, such as bitterness, are universal across all cultures. Others, such as sweetness, however, are more spatially varied due to habitat and culture. This trend applies to non human primates as well. The unfortunate part is that scientists still struggle to ascertain the extent to which these traits are genetically influenced and the extent to which they are trained behaviors, particularly in cultures in which taste sensitivity varies between genders.
One culture studied for taste sensitivity was the Inuit of Greenland. The author of this study, Claude Marcel Hladik, focused on salt. The fact that salt’s concentration in the natural environment varies so much around the world (think coast v: plains) means that it is a great taste sensitivity to study for more information on comparative genomics.
The Greenland Inuit diet consists primarily of seal meat and fat, with occasional starches throw into the mix. The seal meat is always boiled in water and not salted. This is an important practice. Living off of the sea, it is easy to consume too much salt, and the Inuit are always wary of this. They safeguard against it with a number of mechanisms, including: not salting their food, using the freshest drinking water possible, and keeping very well hydrated. The importance of this last point is further increased by the high protein content of their diet. A diet high in protein induces higher levels of dietary induced thermogenesis (DIT, or TEF, thermal effect of food) which in turn creates a strong need for proper hydration. Therefore, the Inuit very carefully control their food and water preparation.
The most important way for the Inuit to do this is to use the freshest possible drinking water. They find this water with the help of their tastebuds, which are nearly super human in their salt detection abilities. The Inuit can discern minute concentration differences water, and they outscore nearly every other culture’s sensitivity by an order of magnitude.
The Inuit obtain this fresh water, traditionally, in a very particular, almost sacred tradition. They trek up into the hills where the freshest waters can be found. They look for the deepest blue-green colors. Then they test various ices for salt content, based on taste alone. The colder the material tested is, the more difficult discerning the taste is. Wow. Cool. Sensitivity is key.
This taste sensitivity is vastly more acute in Inuit women than in men (though both genders still are lightyears more sensitive than the rest of humanity). This is most likely due to the fact that ice gathering is a typically female task. What this fact doesn’t tell us is the extent to which this adaptation is genetic. It is possible that women were selected for their ability to discern salt concentrations. However, it is also (more?) plausible that this is a trained behavior.
What’s more, coastal cultures in Papua New Guinea experience similar effects–they also have salt sensitivities higher than the other, more “normal,” “western,” or landlocked cultures–but not to the same degree. Hladik concludes that this is because the New Guinea tribes consume less protein than the Inuit, and therefore have decreased hydration needs. This tells us that taste sensitivities are a direct result of necessity. Very cool stuff.
Nonhuman primates have no sensitivity for sodium, save for macaques. This fact is interesting, because it demonstrates a clear link between the macaques and their relatively new coastal habitat. Other primate species tend to ingest sodium in small quantities by other means, whether by geophagy (consumption of clay) or by eating termites. In this case, the sensitivity is likely absent because the risk of over-consumption is absent.
What about sensitivity to other tastes?
Hladik looks at newborns to explore innate taste sensitivities. He doesn’t have much a choice, and in fact anyone who studies taste generally doesn’t have much of a choice, either. Beyond infancy, cultural norms become increasingly important, and it becomes difficult to discern a genetic predisposition from cultural conditioning.
Newborns of both human and other primate species have a very narrow range of sensitivity to bitter tastes. Nearly every human being experiences bitterness the exact same way. The few species that vary outside of this range, such as the primate Callithirx Argentata, have different adapted digestive systems. They have a low sensitivity to bitter substances because their guts are more tolerant of poisonous chemicals.
Humans, on the other hand, have a very specific intolerance of bitter chemicals. For this very reason, infants easily identity and have distaste for tannins. This adaptation prevents against the risk of being poisoned. Tannins also inhibit intestinal absorption when they bind to proteins, which makes this universal adaptation even more important for health and survival.
The comparison of taste thresholds varies widely among primates for sugars, however. This is because sugar is far less toxic, for example, than hemlock. Fructose sensitivity appears to vary based on both genetic and cultural factors. This is demonstrated in one experiment comparing sensitivity between African tribes. In pygmy tribes that reside in heavily-fruited forests, fructose sensitivity is fairly low. Just about all fruits taste the same to them, and they do not actively seek out or have to expend much energy to gather these fruits. Fruit is one of their staple foods, and is plentifully available, so it is not necessarily prized. Cultures outside of the forest are much more sensitive to the taste of fruit. This indicates that some sort of selective pressure for fruit sensitivity is at work outside of the forests, where fruits are scarce and more important to detect and eat.
Non human primates also demonstrate a wide range of fructose sensitivity due to different levels of access to the fruits. Some primates live among the trees and have great access to fruits, and therefore have a lower sensitivity. Other primates, such as macaques and chimpanzees, must travel great distances and expend a lot of energy to obtain fruit. It is thus of paramount importance to them that they consume a lot of fruit, and that they can detect it easily. This is assured by hedonism. Macaques and chimpanzees love fruit.
As a final point, positive responses in non-human primates are not limited to sugars. Chimpanzees in Gabon “obviously take great pleasure in cracking ants under their teeth and reducing them to a juice.” According to Hladik, “this activity requires attention and skill, and the reward must be adaptive.” Again, we are pointed to great rewards–this time outside of taste!–for the sake of necessity.
So what does this all mean? Well. We have genetic adaptations for certain tastes. This is really cool. They help ensure survival and proper nutrition. However, taste is an enormously complicated subject, tied up in biology and culture and tradition, and we still have a lot to work through on the effects of all these things. This information on sensitivities just gives us a bit of background to our food stories, and helps to contextualize our sense of taste and our cravings. I like thinking about history when I eat, and this is another cool way to spin on that.