The researchers found that scavengers, or species that eat food at high risk of microbial contamination, have more acidic stomachs. This acidity allows the stomach to act as a filter, effectively controlling which microbes can pass through the stomach to the gut.
One surprise was that, while the researchers classified humans as omnivores, human stomachs have the high acidity levels normally associated with scavengers. Meanwhile, the literature shows that medical treatments – from surgery to antacids – can significantly alter the acidity in a human stomach.
“This raises significant questions about how humans have evolved, our species’ relationship with food over time, and how modern changes in diet and medicine are affecting our stomachs, our gut microbes and – ultimately – our health,” Beasley says. “Those are questions the research community is already exploring, and the answers should be interesting.”