Acid stomach, an omnivorous feature

What did our ancestors really eat? It’s up to this question to try to answer Aymeric de Poyen, nutritionist dietician, on his website. Extract:

“On the other hand, there is another interesting physiological aspect of which we speak much less: the acidity of the human stomach. Indeed, in light of this acidity, it could be that our ancestors had scavenging behaviors!

Thus, in a study on “the evolution of gastric acidity and its implications for the human microbiome”, a team of university researchers examined the level of acidity of the stomach of about sixty animal species. It shows that the highest levels of acidity correspond to carnivorous and scavenging species, while low acidity levels are associated with herbivorous species. This could be explained, according to them, by the role of “disinfectant” played by acid gastric juices released by the stomach during digestion.

Indeed, pathogens are much more numerous in meat (especially when it is in decomposition) than in fruits and plants. Carnivorous and scavenger species eliminate these pathogens thanks to a very acidic gastric pH, whereas herbivores do not need such acidity. Moreover, it is rather favorable for them to have a stomach that does not kill too many bacteria, the latter being necessary for ruminants.

However, the authors point out that the very acidic pH of the human stomach brings it closer to carnivorous animals, even scavengers, than herbivores. Thus the gastric pH in humans was measured at 1.5, whereas in the African vulture, scavenger par excellence, it is 1.3. In this, humans are very different from some great apes, whose gastric pH is much less acid (3.7 in the baboon, yet itself omnivorous). To explain such acidity in humans, they therefore hypothesize that our human ancestors may have been pure carnivores or vegetarians, but rather omnivores sometimes scavengers. A piece of information that allows us to take a new look at this endless debate! “

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