Whether it is miso or kimchi in Asia, wines, cheeses and sauerkraut in the West, or cauim and caxiri in South America, people all around the world consume a lot of fermented food and drink a lot of fermented drink. They also, as this list suggests, choose what to ferment with deliberation. Besides the obvious pleasures of inebriation, appropriate fermentation can both release otherwise unavailable nutrients from a foodstuff and assist in its long-term preservation.
Overall, fermented products comprise between a fifth and two-fifths of an average human diet, and there is archaeological evidence to suggest people were fermenting grains to make beer as long ago as 6,000 years. But that is an evolutionary eye-blink. So Katherine Amato, an anthropologist at Northwestern University in Illinois, found herself wondering just how far back in time a predilection for the fermented goes. As she reports in the American Journal of Physical Anthropology, she discovered that several other primate species also feed on fermented foods. Moreover, though they are not as avid about them as human beings are, their choices seem equally deliberate.
Dr Amato’s starting points were studies published in 2015 and 2019 which showed that the genes encoding two proteins involved in handling fermentation products—alcohol dehydrogenase, an enzyme that processes ethanol, and HCA3, a receptor molecule which triggers an inflammatory response to organic acids produced by fermentation-inducing microbes—first appeared in the line that led to Homo sapiens some 10m years ago. This suggests that a transition in eating habits occurred about then. So, primates being a well-studied order, she decided to investigate those habits in other members of the group.
She began this investigation in the library—or, rather, its modern electronic equivalent. She read through databases, books and papers, and came up with 151 biologists who had collected information on primates’ feeding behaviour in the field. She emailed each of these researchers to ask if any had noticed fermented fruit being among the things that the animals they were studying ate. Several dozen replied that they had. Using these responses, she compiled data on the diets of 40 species, including gorillas, chimpanzees, baboons, macaques, capuchins, lemurs and spider monkeys, from 50 places in Asia, Africa and the Americas.
At first sight, the results were disappointing. Dr Amato and her colleagues found that only 15 species had been seen consuming fruit in the late (and therefore obvious) stages of fermentation. Also, such fermented fruit made up, at most, 3% of those species’ diets. A little more probing, however, revealed something interesting. Of the 44 types of fruit eaten in an advanced state of fermentation, 16 had tough husks that the animals could not easily open unless they were first fermented, and 25 contained digestion-impeding or toxic chemicals like tannins and alkaloids that fermentation tends to destroy.
Presumably, these are foods which would not be available to animals that could not cope with their fermented nature. And even a 3% extension in dietary range is, in evolutionary terms, worth having. It therefore seems probable that even though other primates are not in a position to encourage fermentation deliberately, in the way that human beings do, they are taking advantage of it to broaden the range of their diets.
As it turns out, the relative modernity of human alcohol dehydrogenase and HCA3 may be a canard. Several of the fermented-fruit-eating primates alive today split off from the line that leads to people well over 10m years ago. Presumably, they have evolved their own genetic arrangements for dealing with fermentation products and the microbes that produce them. Nevertheless, Dr Amato’s work suggests that human beings’ love of the fermented does, indeed, have deep evolutionary roots. Cheers! ■