Capuchin monkeys have been cracking nuts with stone tools for 3,000 years
Capuchins carry the largest brain relative to body size of any primate besides us, and they use it. Wild groups pick hammer stones by weight, place nuts on stone anvils and strike. Excavations in Brazil in 2019 showed some populations have kept this stone-tool culture going for at least three millennia.
Capuchins are New World monkeys ranging through the forests of Central and South America as far south as northern Argentina, most abundantly in Brazil. Portuguese explorers named them after Capuchin friars, whose brown hooded robes matched the monkeys' colouring. The group's classification remains contentious: in 2011 Jessica Lynch Alfaro and colleagues proposed splitting the robust capuchins into their own genus, Sapajus, apart from the slender gracile capuchins in Cebus. Her genetic work dates their split to about 6.2 million years ago, possibly when the Amazon River divided their ancestors.
Of all the neotropical primates, only capuchins regularly use tools in the wild. Learning the hammer-and-anvil technique takes years and is passed on by watching others. The tufted capuchin shows remarkable patience: it drinks the juice of palm fruits, discards them, then returns once they have hardened and cracks them on a boulder with river stones hauled from as far as a mile away, some as heavy as the monkey itself. Their diet is broader than their relatives', spanning fruit, pith, insects, frogs, crabs and even other primates.
Social life is organised by rank. Groups usually hold 10 to 35 animals, often dominated by one male, though white-headed capuchins have both an alpha male and an alpha female. They mark a core territory with urine, groom to keep peace and communicate with a range of calls. Females give birth every two years after a gestation of 160 to 180 days, and infants ride on their mother's chest, then her back. Wild capuchins live 15 to 25 years, but captive individuals have reached 50.
They have even been taught money. In 2005 experiments, trained capuchins began treating tokens as a medium of exchange, adjusting sensibly when prices changed and showing the same loss aversion seen in human investors. Adults measure 30 to 56 cm with an equally long tail and weigh 1.4 to 4 kg.
Source: Capuchin monkey
