If you’ve ever watched chimpanzees interact with one another at the zoo – or even in the wild – chances are you will have marvelled at their human-like dexterity, social skills, and body parts.

This is no wonder, since the chimpanzee is the human’s closest living relative in the animal kingdom, with our evolution the reason for our more complex thinking and way of life.

And a new study from a team of universities in the US, UK and Japan have made a breakthrough when it comes to one of the most iconic part of our evolution: the use of tools.

In the new study, which was recently published in the Journal of Human Evolution, the team observed the natural behaviors of chimpanzees living in Bossou, Guinea, to determine their preferences when it came to the tools that they used.

The results of the study showed that our similarities with these creatures continues into the present day.

In the experiment, the team introduced new types of rock to the animals. These rocks were unfamiliar to the chimpanzees, who use rocks to crack nuts for consumption.

Each rock was chosen for its distinct properties. These were categorized by the team before they were set before the chimps, with factors including their hardness and elasticity taken into account, as the researchers explain in the paper:

“We measured rocks using three different standard mechanical tests. Although these measures were not all developed for stones, they have been adapted to allow for measurements of fine-grained rocks.”

All kinds of different stones were included in the study, with other variables taken into account too. These included introducing each chimpanzee to various different numbers of stones, and offering them multiple of the same kind of stone. This helped the researchers to understand if the chimpanzees’ preferences were due to the actual material itself, or something else like  abundance or lack of choice.

Due to the materials available in the chimps’ natural forest habitat, the researchers found that the majority of the stones they offered were better in both hardness and durability than those typically available to the chimpanzees.

Theoretically, this would mean that the majority of the rocks were more effective for nut cracking – both in terms of ease of cracking, and the ability to crack multiple nuts – than the rocks the monkeys were familiar with.

Throughout the experiment, the scientists observed several things, including chimps’ choice of ricks and the efficiency with which they were able to crack a nut with their chosen stones. Notably, many of the chimpanzees chose to use the rocks as tools, by creating a hammer and anvil with two rocks (one to hammer the second with, as an effective method of cracking the nuts open).

Fascinatingly, the chimpanzees consistently chose the hardest of the stones for their hammer, and softer stones for their anvils. This led the researchers to believe that, rather than focusing on the aesthetics of a rock, the chimps had an instinctive knowledge of which material to use for which purpose – even though they weren’t familiar with the particular kinds of rocks. And interestingly, as the team explain, there was a social element to their choices too, with younger chimpanzees copying the behavior of their elders:

“Selectivity of rock types suggests that chimpanzees assess the appropriate materials for functions by discriminating these ‘invisible’ properties. Adults identify mechanical properties through individual learning, and juveniles often reused the tools selected by adults.”

This is interesting for many reasons, but one thing that the researchers noted was what the chimps’ behavior can tell us about human evolution too.

In this experiment, the monkeys were introduced to new technology of sorts, and adapted through a kind of group learning mechanism so that they all knew the best rocks to use in no time. This tells us a lot about how our own species have adapted through time and place, too:

“Hominins may not have needed to directly understand the mechanical properties of stone to canalize the selection patterns on only a few specific rock types. Instead, as seen here in this experiment, a combination of individual learning with some social enhancement can lead to rapid enforcement of the most efficient tool use.”

This experiment shows evolution in action, as the chimpanzees rapidly adapted to the new technologies in order to go about their daily tasks more efficiently and effectively, learning through their social connections to do so.

Not only enhancing our knowledge about chimpanzee behavior, this valuable study also gives us new information about how humans began to evolve, reinforcing and enriching what we already knew about early versions of our own species:

“Selection of specific rock types may be transmitted through the reuse of combinations of rocks. These patterns of stone selection parallel what is documented for Oldowan hominins. The processes identified in this experiment provide insights into the discrete nature of hominin rock selection patterns in Plio-Pleistocene stone artifact production.”

Armed with their hammers and anvils, the chimpanzees found newer and better ways to accomplish their desires – just like we do, every time we pick up a shiny new cellphone.

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