Recently, researchers discovered chimpanzees in Guinea, West Africa, for whom freshwater shellfish were a year-round dietary staple. From ScienceDaily:
The study began in 2012 when the researchers first observed the chimpanzees fishing for crabs. For two years, they documented the demographics and behavior of these chimps, while also analyzing and comparing the nutritional value of the crabs to other foods in the chimpanzees’ diet.
Crabbing, they learned, not only took place year-round — without regard to season or fruit availability — but intriguingly was negatively correlated with the chimps’ consumption of ants, another diet staple. Mature males were the least likely to consume aquatic fauna.
“Energy and sodium levels in large crabs are comparative with ants,” explains Koops, “leading us to hypothesize that crabs may be an important year-round source of protein and salts for females — especially when pregnant or nursing — and for growing juveniles.”
The study further sheds light on our own evolution, by showing that fishing behaviors may not be restricted by habitat as initially assumed.
“This isn’t the first case of non-human primates eating crabs,” points out senior co-author Tetsuro Matsuzawa, “but it is the first evidence of apes other than humans doing so. Notably, previous observations were from monkey species in locations consistent with aquatic faunivory — lakes, rivers, or coastlines — and not in closed rainforest.”
“It’s exciting to see a behavior like this that allows us to improve our understanding of what drove our ancestors to diversify their diet.”
Paper. (paywall) – Kathelijne Koops, Richard W. Wrangham, Neil Cumberlidge, Maegan A. Fitzgerald, Kelly L. van Leeuwen, Jessica M. Rothman, Tetsuro Matsuzawa. Crab-fishing by chimpanzees in the Nimba Mountains, Guinea. Journal of Human Evolution, 2019; DOI: 10.1016/j.jhevol.2019.05.002 More.
This is a classic “evolution” story—the discovery is interesting but the extrapolations are pretty far-fetched. And it’s understood that we are just supposed to accept them at face value. Some questions:
1, Why did researchers assume that chimpanzees wouldn’t eat shellfish if they were easy enough to catch? After all, they were willing to eat ants.
2. Why assume that shellfish gathering is restricted by habitat?
The human evolution hook is “The study further sheds light on our own evolution, by showing that fishing behaviors may not be restricted by habitat as initially assumed.” But why did the researchers assume that fishing would be restricted by habitat? Hungry animals eat what they can.
Also: “It’s exciting to see a behavior like this that allows us to improve our understanding of what drove our ancestors to diversify their diet.” Hunger wasn’t a strong enough driver?
If a minor note about chimpanzee behavior needs to be inflated into a claim about human evolution, that’s most likely because not much is known about human evolution and what is known does not fit the grand narrative. Talk about a fishing expedition!
Some other human evolution claims: Eating fat, not meat, led to bigger human type brains, say researchers.
Earlier discussion of the fat theory.
Starchy food may have aided human brain development
Do big brains matter to human intelligence?
Human evolution: The war of trivial explanations
What great physicists have said about immateriality and consciousness