After living through an outbreak, the monkeys started side-eyeing suspicious snacks too

In early 2020, while humans were wiping down their groceries, a troop of Japanese macaques at a Texas sanctuary was living through an outbreak of its own — and, researchers now report in Royal Society Open Science, the survivors changed their habits in a very familiar way. Macaques that had been sick, or watched others fall ill, became noticeably warier of a tasty treat that merely looked contaminated, even though nothing about it was actually dangerous and the monkeys had no way of knowing how the illness spread. Monkeys without that experience tucked in happily. 'Even with no knowledge of how disease is transmitted, being exposed to others getting sick and dying changes the likelihood of engaging in behaviors that potentially could lead to some form of sickness,' says co-author Federico Rossano of UC San Diego. Disgust, it turns out, may be an ancient survival instinct we share — the original food-safety inspector.