Sometimes, we humans let our dumb values prevent us from taking biological realities seriously. Take pooping, for example: People have decided pooping is gross, even though it’s a thing that most of us do literally every day. Now, some scientists think that even cannibalism is worth another hard look.
Cannibalism naturally occurs in lots of species of insects, fish, and even mammals. And despite our aversion to it as a so-called “civilised” species, cannibalism seems to serve a purpose. A team led by UC San Diego researcher Benjamin Van Allen reviewed past research on cannibalism and came to the conclusion that it might help to limit disease spread in some populations.
“We’ve been looking at cannibals individually,” instead of cannibalism’s effects on entire species, study co-author Bret Elderd from Louisiana State University told Gizmodo. “We’re not advocating that cannibalism is good, but instead that cannibalism is not automatically detrimental.”
The benefit of eating one’s own kind is that members of the same species have all the nutrients you need, in the right amounts. But they also can carry the exact pathogens that can get you sick. Still, diseases don’t have perfect transmission rates, and there’s no guarantee a cannibal will get sick from eating a sick relative.
The team looked at lots of past research on certain diseases in several different species of insects, fish, and frogs. The fall armyworm, for example, can suffer from a specific virus that prevents it from growing larger, making it look like a tasty snack to a healthy caterpillar. But if healthy caterpillars are eating sick ones, it begs a question: will the species succumb to the disease, or will fewer hosts help the population to prevail?
On reviewing the literature and after conducting experiments, the researchers found that cannibalism can actually reduce the prevalence of a pathogen in a species. But this is not necessarily true. In communities where multiple individuals feast on the same diseased corpse, the population could instead succumb, due to the number of infections being greater than the number of infected hosts eaten. The team published their work in The American Naturalist journal.
I sent the paper to a few researchers who said it was interesting, but did not have time to send specific comments—I will update the post when I hear back.
Eldert thinks that knowledge of the benefits of cannibalism to a population could help people deal with things like pest outbreaks. The fall armyworm, for example, is a pest both in the United States and Africa. But “cannibalism can have potentially broad scale applications and impacts on biocontrol, he said. “If you don’t understand it, you can’t use it as a tool to manage pest outbreaks.”
As a final note, you obviously shouldn’t eat your neighbour. However, Eldert would like people to take another critical look at how cannibalism works in nature. It might yield some important scientific insights. [The American Naturalist]