Acid Perception in Primates
But let’s face it: you and I are not worms. We are not fish. We are primates. Instead of sensing the presence of acidity in an aqueous environment using receptors on the outside of our body, we need to actively ingest a substance to determine whether or not it is acidic. Now, anyone who’s ever juiced a lemon or a lime when you’ve got a cut on your hand knows that’s not strictly true, but for the purposes of sour cocktails, it remains the governing truth. Here’s professor Dan McCall from the Gettysburg Odor and Flavor lab explaining how our taste receptors identify a given taste. If you can believe it, this is from WAY BACK in Episode 7! That’s almost 5 years ago!
Tune into the full interview in the audio player to hear professor McCall’s Clip.
Notice that professor McCall isolates the way we perceive acid and salt from the way we perceive sweet, bitter, and umami flavors. This is because these two tastes operate using ion channels, rather than the slightly more specialized “lock-and-key” receptors for other tastes. To me, this connection between acid and salt seems important, especially when we’re talking about a sour cocktail often served with a salted rim.
But perhaps more important than our mere ability to perceive acidic tastes is the reason why we tend to crave or prefer them, which is almost certainly a phenomenon that occurred much closer to modern humans in the evolutionary tree of life. So in our next phase of this journey, we get to time jump more than 400 million years closer to the present day.
One possible explanation for our preference for sour flavors is that about 60-70 million years ago, the common ancestor of monkeys and primates lost the ability to produce endogenous vitamin C due to a genetic mutation. Vitamin C, of course, remains a very important nutrient for humans, and it does play a very, VERY direct role in the development of sour cocktails. But before we were mixing up grogs and punches (supposedly) to fight scurvy, and gin and tonics to fight malaria, our fuzzy forebears were stuck sourcing their Vitamin C primarily by foraging for fruits and berries.
This brings us to a fascinating little moment in the history of human evolution: the moment that primates descended from the trees and decided to stay on the ground. This “decision,” if you can call it that, is what prompted us to begin walking upright and to form social groups capable of warding off terrestrial predators. It also happens to be the historical moment where our need for vitamin C experienced a collision with our affinity for alcohol.
Here’s past guest Mark Forsyth, author of A Short History of Drunkenness, explaining the “Drunken Monkey Hypothesis.”
Tune into the full interview in the audio player to hear Mark’s Clip.
It’s also speculated that sour tastes are a kind of safety signal in rotting or fermented foods – one that says, “hey, this is probably okay to eat.” This is relevant because, as our primate ancestors foraged for the nutrients they needed, they were bound to encounter lots of ripe fruits rotting on the ground, at which point they were faced with the decision: to eat, or not to eat?
Here’s distiller Bryan Davis, who does an excellent job breaking down the complex battle between bacteria and yeast that occurs on fermenting or rotting substances.
Tune into the full interview in the audio player to hear Bryan’s Clip.