Why do we fish? At a time of eons ago, our primarily fruit-eating ancestors placed their hands in the water to catch and eat aquatic life by accidentally supplementing their diet with nutrients that began a brain development process that eventually led to humans. But how did it begin?
According to a research group from Kyoto University, a potential hint may have been made thanks to observations of man's closest genetic relatives: chimpanzees. The researchers report the first ever evidence of wild chimpanzees that usually catch and eat freshwater scrapers. Writing in the Journal of Human Evolution describes the team year-round freshwater crab fishing behavior ̵
"Our findings also indicate that aquatic fauna may have been a regular part of the hominin diet and not just a seasonal rainfall."
The study started in 2012 when the researchers first observed the chimpanzees that fished for crabs. For two years, they documented the chimpanzees' demographics and behavior while analyzing and comparing the nutritional value of the crabs with other foods in the chimpanzee's diet.
Crabbing they learned not only took place year-round – regardless of season or fruit availability – but was fascinatingly negatively correlated with chimps's consumption of ants, another diet. Older men were least likely to consume aquatic fauna.
"Energy and sodium levels in large crabs are comparable to ants," explains Koops, "which leads us to assume that crabs can be an important annual source of protein and salts for women – especially when pregnant or nursing – and for the cultivation of young people. "
The study further sheds light on our own development by showing that fishing behavior must not be limited by habitat as originally assumed.
"This is not the first case of non-human primates eating crabs," points out high-level co-author Tetsuro Matsuzawa ", but it is the first evidence for other monkeys than humans do. In particular, it was earlier observations from monkey species in places in accordance 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 led our ancestors to diversify their diets. "
Captive chimpanzees spontaneously use tools to excavate underground food
Kathelijne Koops et al. Crab fishing at chimpanzees in the Nimba Mountains, Guinea Journal of Human Evolution (2019). DOI: 10,1016 / j.jevol.2019.05.002
Could some chimpanzee crustaceans want to give traces of human development? (2019, May 29)
May 29, 2019
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