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A chimp eating prey she killed with a spear

A chimp eating prey she killed with a spear

Compared to other primates, humans have a very weird diet. In particular, we eat way more meat than even the most adept spear wielding chimp. Or at least, most of us do.

This odd habit of eating a lot of meat was also one of the first things about our diets to change. As early as 2 million years ago our ancestors might have been eating significant quantities of meat.

What was it that drove this hominins to become butchers? Why did evolution favour this strategy?

Many link it to a need for more energy. Perhaps because our brains started getting bigger. In order to test this, they went and looked at pregnant chimps. Seem a bit irrelevant? Well bear with these researchers, there is a point to this.

Pregnant chimps hold the key

Many theorise that the extra energy from meat may have been needed to fuel our bigger brains. However, scientists can’t inflate the brains of animals to test whether this is the case. So they looked for another possible cause of increased energy needs.

As the title – and now subtitle – of this article kind of gives away, they found the answer in pregnant chimps.

Pregnancy puts a huge strain on the body. It drastically increases the energetic needs of a person (since they do have to fuel more than one person now).  So if needing extra energy really drove earlier hominins to eat extra meat, then pregnancy should have a similar effect. And since the researchers can’t examine any earlier members of the human family, they chose to study chimps instead.

Sure enough, they found that pregnant chimps were eating more meat than the average member of their troupe.

Chimps are hunting red colobus monkeys into decline. Here's them tearing one apart.

Chimps are hunting red colobus monkeys into decline. Here’s them tearing one apart.

This helps establish that a need for extra energy can drive primates to eat more meat, making it more plausible earlier hominins also took this route. Additionally, it shows that chimps are capable of understanding when they need more energy and that meat can be a good source of it (albeit, perhaps only at a subconcious level). Again, this indicates that our ancestors might have naturally known that meat had what they needed, with minimal evolution required.

As an interesting aside, the researchers also found that meat consumption was linked to status. Females higher up in the tribe got to eat more meat, regardless of their pregnancy level.

tl;dr

Pregnant chimps eat more meat because they need more energy. This suggests our ancestors begun eating meat when they needed to fuel their big brains.

References

Boyd and Silk. 2014. How Humans Evolved.

O’Malley, R. C., Stanton, M. A., Gilby, I. C., Lonsdorf, E. V., Pusey, A., Markham, A. C., & Murray, C. M. (2016). Reproductive state and rank influence patterns of meat consumption in wild female chimpanzees (Pan troglodytes schweinfurthii). Journal of Human Evolution, 90, 16-28.

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10 Comments

Wyrd Smythe · 21st November 2015 at 5:51 pm

“Well bare with these researchers,…”

They’re naked researchers? Cool! 😀

    DrFinlay · 21st November 2015 at 6:07 pm

    Closet naturists. Who knew?

      Adam Benton · 21st November 2015 at 6:39 pm

      It helps ingratiate them with the chimps

    Adam Benton · 21st November 2015 at 6:39 pm

    I must reiterate, you saw nothing

      Wyrd Smythe · 21st November 2015 at 7:48 pm

      Oh, but in this case I saw everything! XD

Peter Kvint · 21st November 2015 at 6:08 pm

Pregnancy is so long that the pregnant chimpanzees do not need any more food than normal. The chimpanzees are breastfeeding on the other hand needs more food.

Jim Birch · 21st November 2015 at 11:06 pm

In addition to a higher energy density, meat also contains more protein, fats, iron, calcium, etc, and is more or less free of the array of toxins found in plants, especially wild non-cultivars. Could this be a factor?

Paul Braterman · 21st November 2015 at 11:38 pm

“it shows that chimps are capable of understanding when they need more energy and that meat can be a good source of it”; no. She just feels like eating meat. That’s how it works. No understanding needed, least of all an understanding of the concept of energy, and the fact that meat has more per gram than fruit.

    Adam Benton · 22nd November 2015 at 12:51 am

    Hence the reference to the subconcious. She might not be aware of the specifics, but her body can recognise (and encourage) the benefits of eating meat. In much the same way they also have an innate preference for cooked food. I’m not trying to imply they’re doing some calorie counting in their head.

Cynthia Echterling · 22nd November 2015 at 3:56 pm

Pregnant women almost always get cravings and they change over time. I remember going through cabbage and olives, then carrots, then ham and cheese sandwiches, then corn flakes. I don’t even like corn flakes. BTW, Adam, do you know if chimps have discovered cracking open bones to get to the marrow yet?

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