Breaking a nut, stripping a branch, shaping a piece of stone: the line between the animal that uses an object and the one that shapes it is finer - and more surprising - than one might think. A brief and concrete overview of the true tool makers in the living world.
Before designating champions, we must agree on the terms. A widely accepted definition describes the use of tools as the employment of an object detached from the environment to modify the shape, position, or state of another object, another organism, or even the user themselves. An important condition: the animal holds or carries this object at the moment of use (or just before), and it is indeed the animal that ensures its correct orientation.
In short: a tool is an object used to alter the position or shape of another object or an individual. **Making** a tool is a step above: it requires modifying the object before using it. Stripping a branch, shortening it, sharpening its tip, detaching a flake from a pebble... this is what we call making.
**Nota Bene: the proto-use of tools.** When a capuchin monkey strikes a nut against a root or a very hard stone to open it, there is no intermediary between its hand and the nut: the support acts as an anvil. This behavior is classified as proto-use of tools, rather than the use of tools in the strict sense. This, as we will see, does not detract at all from the finesse of the maneuver.
Ask the question around you: who made the first stone flakes? You will be told Homo habilis or Homo erectus. However, there are flakes, sharp tools, pieces intended for cutting or crushing, that were produced by a bonobo named Kanzi, as part of experiments conducted in the United States.
Let's be honest about the protocol: a human first performed the rudimentary gesture in front of him, and the behavior has never been observed in the wild. But with his bonobo hands, Kanzi indeed made stone tools, then created and improved over the years a whole range of objects suited for the tasks at hand. However, his thumb is short and narrow, he uses precision grips sparingly, and he is apparently lacking the long flexor muscle of the thumb, that famous muscle deemed essential.
This is not an isolated case, and it is not recent. Since 1993, we have known that a great ape is capable of shaping stone without possessing the so-called human anatomical traits. Worse: as early as 1972, an orangutan managed to do it, with a thumb even shorter than that of the bonobo. And a male capuchin, whose thumb is not even fully opposable, produced a flake to pierce a plastic film, before using a second tool, a stick, to reach the coveted syrup.
If this potential exists in a South American monkey as well as in African and Asian great apes, it could date back to their common ancestor, around 40 million years ago. We are far from the 1.8 million years of Homo habilis.
The classic argument rests on a few anatomical features: a long and opposable thumb, equipped with a long flexor muscle, wide last phalanges, and the ability to grasp precisely and forcefully between the thumb and index finger. The supposed conclusion: only humans possess all of this, therefore only humans shape stone. However, each of these criteria crumbles when we look elsewhere.
The first problem: these traits exist in species that neither make nor use tools. Many lemurs have long thumbs, gibbons possess the long flexor muscle of the thumb, and neither group shapes anything. The second problem, symmetrical: species with short or only pseudo-opposable thumbs (such as capuchins, whose thumb pads do not perfectly oppose those of the index) use stones to crack very hard nuts, in Brazil just as chimpanzees do in Côte d'Ivoire and Guinea.
The third problem, the most intriguing. Compare the contours of the last phalanges of the thumb from several species: that of Orrorin tugenensis, which is 6 million years old, resembles ours more than that of Homo habilis, which is much more recent and nicknamed Handy Man. And an even closer phalanx to the human shape belongs to Sue, a 70-million-year-old Tyrannosaurus. Unless dinosaurs invented the biface, this criterion clearly isn't sufficient.
Even precision is not our exclusive domain. By comparing the grips of mouse lemurs (the smallest primates in the world, alongside pygmy marmosets) and tree frogs, we find that their grips are very similar. Some of these frogs have only four fingers, but the first behaves like a thumb: it opposes and allows for precise grips. There is even a frog with a long and opposable thumb. Disturbing, isn't it?
If a bonobo, an orangutan, and a capuchin can shape stone in captivity, why don't they do it in the wild? The first answer: because they have no need for it. Why shape a tool when you already have an effective and economical solution?
Look at the nut-cracking capuchins. They select a suitable support to serve as an anvil: hard, wide, preferably with a small depression to hold the fruit. They then optimize the action itself, its speed and amplitude, and often reposition the nut, sometimes between each strike, to present its most fragile side. The result: fewer strikes needed, and not a single intermediate tool.
The second, broader avenue: the necessity of extracting food seems to be a favorable condition for innovation. Great apes that must seek out nuts, honey, ants, fruits enclosed in shells (chimpanzees, orangutans) have a richer repertoire of tools than others. Among the smaller monkeys, the only habitual tool users are also extractors: capuchins and long-tailed macaques.
And we must recognize the limits of our explanations. In captivity, all great apes spontaneously use tools in various contexts, and many small monkeys do so occasionally. Why does one species start doing it while another does not? No one really knows. What is certain is that it is neither a question of thumb length nor a lack of intelligence.
Among mammals, monkeys remain the most prolific tool users, both in the wild and in captivity. It is among chimpanzees that the truly regular use of tools was first described, starting in the 1960s with Jane Goodall's observations. Since then, the list has continued to grow.
This is not a talent that falls from the sky: a young chimpanzee needs several years of observation to learn how to make a tool. It takes more than four years to master termite fishing, and three to five years to learn how to crack nuts. In other words, there is indeed learning, patience, and imitation of elders.
Above all, chimpanzees (and orangutans) exhibit both forms of flexibility: they use the same tool for different purposes and achieve the same goal with different tools. They sometimes chain sequences of several tools or combine multiple innovations to achieve a result. This flexible and cumulative use betrays intention and planning, not an automatic reflex triggered by a stimulus.
The catalog is worth a look, and it is very concrete. Termite fishing, first: a stick inserted into the termite mound, which is pulled out filled with insects. Then, nut cracking, using both stone and wooden tools. Next, the use of real "harpoons," branches used for hunting.
Less known, yet remarkable: the making of plant "shoes" to protect the feet while climbing spiny tree trunks. This is true functional DIY, shaped for a specific problem.
In addition, there is a whole range of techniques for preparing and extracting food: grinding, pounding, absorbing plant material (sometimes for medicinal purposes), extracting honey from the combs and marrow from bones, digging in the ground to reach tubers. And even personal grooming: chimpanzees and orangutans use sticks to clean their teeth and nails.
The turning point is that these techniques are not the same everywhere. Some vary from one group of chimpanzees to another: those in Uganda, Ivory Coast, or Guinea do not perform exactly the same gestures, do not favor the same materials, and do not solve the same problems in the same way. Many researchers no longer hesitate to speak of traditions, even cultures.
The most amusing example comes from elsewhere: long-tailed macaques have been observed using human hair as dental floss. And this behavior seems to be the result of genuine teaching from mothers to their offspring. Transmission, social learning, local variation: the ingredients of tradition are present.
The same is true for Western gorillas, where the plants consumed and the techniques used to manipulate certain foods differ among groups... which nonetheless have access to the same resources. The properties of the foods may play a role, but the hypothesis of traditions passed down from generation to generation is taken very seriously. Understanding how a young gorilla learns from its mother is to understand how a culture is formed.
In wild orangutans, tool use exists and the repertoire is varied: extracting fruits and insects, protecting themselves from rain, probing the depth of water... but it is observed less frequently than in chimpanzees. In gorillas and bonobos, it is even rarer. This does not mean they are incapable, far from it.
Place a wooden maze filled with obstacles behind a fence, with a nut at the end, and give them branches: everyone gets involved, each in their own way. Orangutans alternate between hand, foot, and even mouth to guide the nut, and shorten their tool with their teeth as the fruit gets closer. Their oral dexterity can undoubtedly be attributed to their highly arboreal life, where all four limbs grasp branches and only the mouth remains available.
Gorillas, on the other hand, are specialists: they use one hand, and always the same one, exclusively left or right. However, they multiply intramanual movements, between fingers, to reposition the tool, and often employ the grip we know well, that of a pen. They touch more obstacles on average because their movements are more abrupt, but they retrieve their nut like the others.
As for bonobos, they succeed quickly, and the oldest females are the most efficient. The matriarch of a group, Daniela, 43 years old, perfectly illustrates what a planned strategy looks like: she chooses her tool in advance and from a distance, selecting a very curved branch, prepares it by removing bark and twigs that could get stuck in the fence, and then, on site, the curvature allows her to position herself above the maze and see the scene well. With grapes, she did even better: a pointed tip carved at the end of her branch to poke the fruit and bring it over the obstacles. A small cry of satisfaction followed.
Capuchin monkeys are a living demonstration that you don't need a perfectly opposable thumb to be an excellent manipulator. They use stones to crack nuts, throw objects to attack, and use a stick to retrieve food out of reach. The numbers are staggering: some females lift stones weighing 3.5 kilograms while they only weigh 2.2, without crushing the small nut targeted.
Their creativity also unfolds without tools. A small female, intrigued by chestnuts, encountered the problem of the spiky, prickly husk. Her solution, in three steps: soak the husk in water for a long time, test the flexibility of the spikes with her fingertips and lips, return it to the water until they are soft enough, then gradually press with the base of her palms (less sensitive than fingers) while coordinating her right and left hands. What remained were the chestnuts themselves, opened by a series of bites and more delicate gestures with her fingertips.
Another finesse: their habit of tapping, seemingly aimlessly, on small branches, sometimes dead. Individuals fond of worms and larvae likely detect, by sound (low or high) and tactile sensation, the presence of galleries in the wood. A poor man's ultrasound, in short.
And in the maze? The capuchin is the Speedy Gonzales of the group: curious, fast, even too fast. He invented a strategy that no one had used: shaking the device frantically to make the nut jump over obstacles. Despite his small size, the strength of his upper limbs is sufficient. All that remains is to better secure the mazes to see what he can do with a tool...
Lemurs have never been observed using tools in the wild to date. Often considered the least intelligent of primates, they are also much less studied than others, which weighs heavily on the assessment. Is it a lack of necessity in their environment, or a lack of attention focused on them?
An experiment conducted in a zoo in southern France illustrates this difficulty well. The setup: large wooden logs with holes drilled in them, filled with mashed banana at the bottom, and branches available throughout the aviary to serve as tools. The two males approach, curious, sniffing... then nothing. Days go by. We strip the branches and place them close to the setup: nothing. We put them on the setup: nothing. On the last day, we directly insert the branch into the hole: one of the males grabs it, pulls it out, observes it for a fraction of a second, and abandons it with the banana on top.
A failure, then, but an instructive one. The task of the probing stick corresponds to natural behaviors in some species, but not in these, and the food motivation was likely lacking. This says nothing about their capabilities: a study has shown that lemurs are indeed capable of using tools.
There are still about a hundred species of lemurs to explore, not to mention the lorises. An intriguing lead is emerging: there seems to be a link between manipulation abilities and the way females carry their young, either in their mouths or clinging to their fur. The arboreal environment may have favored manual grasping abilities, which in turn could have helped the young cling to their mother's fur.
The tool is neither a matter of hands nor a matter of primates. New Caledonian crows insert sticks into crevices to extract prey, and they do this whether or not they have observed a conspecific at work. The woodpecker finch, on the other hand, develops its tool use through individual learning, trial and error, rather than by copying others. Two very different paths to the same result.
Some animals remain specialists: the archerfish shoots jets of water beyond the surface to knock down insects, and it employs this technique in no other context. This is referred to as behavioral specialization. In contrast, a behavioral innovation is using a stick to catch food and then using it to clean one's teeth: two ingredients emerge, adaptability and creativity.
And fine manipulation, too, can happen quite well without hands. Faced with boxes whose locks require pushing, pulling, or turning a latch, capuchins and blue-and-yellow macaws have all succeeded in retrieving hidden food, but not with the same means: a lot of fiddling, tapping, and rubbing among the monkeys, followed by a quick opening with hand, beak, and tongue among the parrots, with far fewer exploratory behaviors.
Nota Bene: we like to link tools and large brains, and it is true that a correlation has been established between this behavior and brain size, both in primates and birds. However, brain size does not indicate the number of neurons. Birds possess a very large number of neurons in the pallium, a region involved in functions such as planning, and they reach comparable or even superior numbers in the forebrain compared to primates. It is the neurons, not the cubic centimeters, that carry cognitive abilities.
In terms of archaeology, the benchmarks have shifted significantly. The first stone tools were dated to 2.6 million years ago by a study published in 1997, while the oldest fossils attributed to the genus Homo date back to 2.4-2.3 million years ago. The minimal gap already opened the door to other makers.
In 2010, cut marks analyzed on bones from Ethiopia dated to 3.4 million years ago pushed the hypothesis much further back. Then, in 2015, the Lomekwi site in Kenya yielded numerous stone tools dated to 3.3 million years old: about 700,000 years older than the previously known oldest tools and 500,000 years older than the first humans discovered. A valuable detail: these tools are associated with a forested environment, which undermines the old scenario linking tool emergence to open savanna.
So who made these stones? At that time, australopithecines are known, but in Ethiopia. Kenyanthropus, on the other hand, fits the right area and period, but is primarily represented by a disputed skull. Between 3.4 and 2.6 million years ago, several species potentially linked to the genus Homo coexisted alongside various species of australopithecines, including Lucy.
Fossil hands do not provide clearer answers. Lucy retained only 2 bones out of the 27 in the hand, and many "fossil hands" are composite reconstructions, assembled from bones that may not even belong to the same individual. The small miracle is called Australopithecus sediba, discovered in 2010 in South Africa: about 2 million years old, it has the most complete hominin hand ever uncovered with 20 out of 27 bones... and a very long thumb, closer to that of modern humans than that of Homo habilis itself. Three conclusions are then possible, and all three hold: either the australopithecines made the first tools, or Handy Man is not a Homo, or the anatomy of the thumb simply does not allow for a conclusion.
Archaeology suffers from two implicit limitations, and they are formidable. First, we only study what has been preserved. Second, an object is identified as a "tool" only if it has been modified: a raw stone used as is goes completely unnoticed, and wood, on the other hand, disappears.
The brutal consequence is that if Orrorin tugenensis cracked nuts with raw stones or pieces of wood about 6 million years ago, like a chimpanzee, we will never know. And when tools and hominin remains are found together, we still need to determine whether these bones belong to the toolmaker... or its prey.
The oldest known wooden tools are spears and double-pointed sticks made of spruce and pine, discovered in Schöningen, Germany, dating back over 300,000 years and attributed to Homo heidelbergensis or Homo neandertalensis. But nothing prevents us from thinking that such objects existed long before and were contemporary with still arboreal species.
However, in the living world, the most commonly used material is not stone: it is perishable materials—leaves, branches, wood. The strategies for selecting a branch (size, diameter, length), its preparation, modification, and manipulation can sometimes be extremely complex depending on the task at hand. Therefore, the origins of tools are likely to be traced back well before the appearance of primates—and much of this history will remain forever invisible.
The temptation of ranking remains. In the maze test, adult humans are indeed the fastest and most efficient, ahead of bonobos, children, and orangutans. Their secret weapon: manipulating a tool in each hand, dissociating the right hand that pushes the nut from the left hand that controls its trajectory - a complex bimanual coordination. They also employ a single grip, the precision grip, like holding a pen between the pads of the first three fingers, while children favor power, using all fingers and the palm.
But this "superiority" speaks to something other than intelligence. The most successful adults were those who practiced a sport or music: the best candidate was a rock climber, followed by a cellist. They are not more intelligent; they have developed dexterity in one area and transferred it to another. Add competition (adults seek the best score, children take their time), hierarchy (among bonobos, dominated males have their tools stolen or don’t even access the device), traditions, and learning, and you understand why a success rate never measures intelligence.
What to take away, concretely? That tool-making, including stone tools, is within the reach of several primates, with or without a "human" thumb. That remarkable manipulation abilities also exist in those who use no tools, and even in those who have no hands. That anatomical criteria inherited from the 20th century - long thumb, wide phalanx, precision - are not sufficient to designate a maker.
The next time you see a crow sliding a twig into a crack or a capuchin turning a nut between two strikes, observe the complete sequence: the choice of the object, its preparation, positioning, and correction of the gesture. This is where everything happens. Humans are unique, of course, but so are gorillas, orangutans, and any other species. The tool has never had a monopoly on intelligence, and this intelligence does not escape the great rule of life: diversity.
Author Audrey on 18 November 2024
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