By Andrea Hargraves 
You are Capuchin monkeys They are some of the few primates that use tools in daily life. One of the main uses of the Cerrado and Caatinga are stone hammers and anvils, which are used to break the shell of hard foods, such as jatoba pods and cashew nuts.
In the study published In the journal Scientific Reports, Brazilian researchers show that the relationship between food hardness and tool size is not always as accurate as previously thought.
By observing three Brazilian residents of Capuchin monkeys of the species Sapajus libidinosus and measuring resource resistance, the size and weight of the tools used, and the availability of stones at the site, the scientists concluded that the group’s culture—information preserved across generations through social learning—could also influence selection.
“In one of the three analyzed populations, even when they have stones better suited to a particular resource, they can use disproportionately heavy tools, which may indicate a cultural trait of that group,” he explains. Thiago castlesresearcher at EACH-USP (Faculty of Arts, Sciences and Humanities, University of São Paulo) supported by Fapesp.
The population the researcher refers to lives in the Chapada dos Videiros National Park in Goiás. The comparison was made with two others, natives of Piauí: in the Serra das Confusões National Park and in Serra da Serra National Park capybara100 km from each other.
The tools, in this case, refer to pieces of quartzite and sandstone rock found in places known as collapse sites. These places are frequented by animals exclusively for access to these rocks and anvils. The first ones are beaten by monkeys for food, which is supported by an anvil.
“In Serra das Confusões, when cracking small and less resistant fruits, the Capuchin monkeys use smaller tools. And when they need to open large and hard coconuts, they use large, heavy hammers. In Chapada dos Veadeiros, although they have a wide variety of tools, they They use the heaviest even with the most fragile foods,” says the researcher.
It is no coincidence that in Chapada dos Videiros, researchers recorded the heaviest weight ever lifted by capuchin monkeys. One of these small primates, averaging 3.5 kg (adult male), was filmed lifting a 4.65 kg mallet. “They are real bodybuilders,” Falotico notes.
measurements
The results are the result of careful work. In the three places where the studied populations of capuchin monkeys lived, the most documented foods found at refractory sites were babassu coconuts, jatoba, cashews and manicoba seeds (a close relative of cassava).
The availability of stones is also documented, as well as the size and weight of the tools found. Using a special device, the researchers also measured the resistance of each food found. Finally, they observed and photographed how monkeys from each group used the tools with specific foods.
“We expected to find a very direct correlation between tool size, weight and food, but population Vederos plateau, which has a large amount of rocks and can choose the largest or the smallest, mostly using the largest. This behavior is likely inherited from the ancestors, and is a cultural differentiation from other populations,” says Falotico.
Another example that monkeys have cultural learning is that in other regions of Brazil, such as Serra de Itabaiana, in Sergipe, and Chapada Diamantina, in Bahia, there are also capuchin monkeys of the same sex, stones and the same fruit available. However, there are no cracking sites, hence, the behavior of opening the fruits for eating. At Serra das Confusões, monkeys break down various foods, except for cashews, although they are abundant.
“It is not only resource availability or resource scarcity that determines the occurrence of a behavior, but cultural heritage,” he says.
The researchers are now conducting genetic analyzes of the three populations to see if cultural differences can be detected in the genomes.
The work was supported by FAPESP also through hand bag awarded to Tatiana Valencia In EACH-USP.
human ways
in another work, published In the Journal of Human Evolution, Falotico and a team of archaeologists from Spain, Germany and the United Kingdom analyzed, in a field experiment, the formation of stone chips by capuchin monkeys when they used different types of rock as anvils.
In nature, splinters are formed when these primates hit one stone against another to use the resulting powder to rub their bodies and teeth. It is not known why capuchin monkeys use this product, but researchers believe it may have an antiparasitic effect. In the experiment, anvil smashing of more homogeneous materials produced these types of flakes.
However, monkeys do not use chips, although they are very similar to stone tools found in archaeological sites in different parts of the world. The researchers hypothesize that before the fragments were intentionally made to be used as tools, early humans acquired them by accident.
Likewise, in theory, Capuchin monkeys It may switch to using chips in the future if an innovative individual starts using them and others learn by watching. Therefore, these primates can serve as a model for understanding human evolution,” notes Al-Brazil.
In previous work, the group showed how stone tools used by the capuchin monkey population of Serra da Capivara acquire specific markings according to their use. (read more here)🇧🇷
Comparing the marks on monkey tools with those on humans can help reveal how early humans used these stone tools. With this said, Brazilian capuchin monkeys pave the way for a better understanding of our ancestors.
The article Stone Tools Differences Across Three Groups of Capuchin Monkeys: Physical Characteristics of Food, Environment, and Culture Available at open access🇧🇷
And the study could be a primate model for the origin of chip technology read over here🇧🇷