The recycling of ancestors | The paper

One of the guiding features in the search for precursory signs of what we could generically define as “humanity” is the ability to produce toolsstarting, of course, with stone tools – among the oldest ever found, if only for their very long shelf life that defies millions of years.

We know for sure that stone tools are used by many different animal species: animals such as sea otters, birds and even fish can use stone tools. Some birds, such as the bearded vulture, drop bones on stones to open them and reach the marrow. New Caledonian crows sometimes use stone anvils. A wrasse fish was filmed smashing clam shells against reef boulders to crack them open. Sea otters have been known to fish out small pebbles, place them on their chests, and then open shellfish on them. Where pebbles are not found, they slam their prey against large rocks by the sea.

In primates, many different species use different stones for various purposes. While chimpanzees are the best known tool users in this group of animals, they are by no means the only ones. Studies in Brazil and Panama have shown that capuchin monkeys use stones to crack palm nuts in much the same way as chimpanzees. A research group from the University of Oxford has shown that the use of stones by the Capuchins as tools for cracking nuts dates back to at least the 13th century, more than 200 years before Columbus arrived in the Americas, and is therefore an archaeological behavior documentable. The use of stone percussion tools by chimpanzees and capuchins is also known to produce a durable archaeological record. It consists solely of stone hammers and anvils; however, in some cases, a larger set of fragments is produced. These sharp fragmentary lithic artifacts, however, they lack the attributes commonly used to identify intentional stone flaking.

It is currently assumed, that is, that it is possible to distinguish the production of sharp stone blades through the appearance of the final product, capable of revealing a chip according to a preordained pattern; and precisely this design ability is the characteristic that would be indirectly revealed by the lithic industry of very ancient hominins, and perhaps in evolutionarily older species.

However, a major new study simultaneously questions our ability to recognize intentionally chipped stones and reinforces ideas about how the lithic technology typical of our and other hominin species was derived.

Long-tailed macaques living on certain islands off Thailand use stone strikers to crack open nuts and other food (sometimes so effectively as to drive the local population of one type of oyster to extinction). When processing food, these monkeys often break their hammers and anvils. The resulting assemblage of broken and chipped stones is consistently widespread, both geographically and archaeologically. Now, the important point is that in a newly published work chippings accidentally produced by monkeys were found to have the same characteristics commonly used to identify intentionally made stone tools at some of the earliest archaeological sites in East Africaso much so that experts in the sector have not distinguished the artefacts attributed to ancient hominins from those of apes.

As the authors correctly conclude, the intentional production of stone tools represents an adaptive threshold that has radically altered the evolutionary trajectory of our lineage, but the results of the new study show that A thorough reevaluation of how we define and identify this behavior in the archaeological record is neededto avoid unintentionally mistaking the production of stone chips for the manufacture of blades that can be used as tools.

At the same time, this means that the most advanced lithic industry arose by reusing previously discarded flakesadapting them to new purposes, and hence modifying the percussive behavior dedicated to breaking hard shells in the intentional processing of stone blades.

If this is true, our first and most enduring technology based on the production of tools, which has allowed the survival for millions of years of other species beyond our own, is the daughter of the intelligent reuse of waste materials: a lesson worth to keep in mind even today.