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 bare 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.
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.
