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Science, Why?

The way chimps eat monkey brains could answer questions about evolution

According to a recent study by Arizona State University anthropologist Ian Gilby suggests the chimpanzee’s method of eating baby monkey brains is closely tied to evolution.

It might not be something you’d like to picture, but deep in the Tanzanian National Park chimpanzees are preying on red colobus monkeys to make up the nutrients in their diets.

Whilst species of ape vary between herbivores and omnivores, it is not a revelation to scientists that chimpanzees hunt monkeys for food. The revelation is how they are choosing to eat the monkeys.

After reviewing footage he captured of the chimpanzees in the Tanzanian National Park, Ian Gilby realised chimps eat monkeys differently according to the age of their prey.

Whilst the chimps didn’t have a particular method in how they eat adult prey, they started with the brain when consuming younger prey.

In the study, Gilby wrote: “We tend to just say meat is meat, but we know that the nutrient composition varies.”

“The whole carcass is valuable, but the brain is especially valuable.”

The nutritional value of brains can assist with neurological development thanks to the long-chain fatty acids which are found in the meat.

According to a 1973 study on the eating habits of chimps, the brain has always been a desirable first option.

“The brain is the only organ for which marked preference is regularly shown, and the eating of brain tissue is always a slow, meticulous procedure with a definite undertone of enjoyment.”

Another reason for chimps to go for the brain first is that adolescent monkey skulls, like humans, are softer as they are still forming.

Therefore, attacking the skull is a quick and effective way of eating the kill before competitors have a chance to.

Scientists are still unsure as to why omnivorous apes seek out their prey, as meat is not a necessary staple in their diet.

Jill Pruetz, a biological anthropologist specialising in primatology, suggests apes are hunting for the nutritional benefit of meat.

Meat provides chimps with vitamins A and B12, zinc, copper and iron, which can’t be gained from eating plants.

However, this doesn’t answer why chimps’ source of meat varies so dramatically across the sub-species. In Fongoli, Senegal, home to the notorious Fongoli chimps, the chimps have been studied hunting baboons yet discarding the heads and guts of their kill.

Just as not all chimps eat monkeys, chimps in some parts of the world eat eggs while those in other areas don’t.

There’s still a lot of unanswered questions. Gilby believes the study into the chimps’ eating etiquette provides clues to evolution, suggesting the species which is believed to have lead to human evolution began to eat more meat for the value of fat.

“One of the best ways we have of understanding early hominids is using chimps as a model,” he says.

“Getting the clearest picture of chimpanzee hunting can allow us to make predictions or hypothesis about how the earliest hominids may have behaved.”

You can find out more about the study in the International Journal of Primatology.

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