* These authors contributed equally to this work. Paleoanthropologists use the distinctive characteristics of flaked stone tools both to distinguish them from naturally broken stones, and to interpret the behaviour of the hominins that produced them 4 . Suggested hallmarks of the earliest stone tool technology include (i) controlled, conchoidal flaking 5 , (ii) production of sharp cutting edges 6 , (iii) repeated removal of multiple flakes from a single core, (iv) clear targeting of core edges, and (v) adoption of specific flaking patterns 7 . These characteristics underlie the identification of intentional stone flaking at all early archaeological sites 3,5,[7][8][9][10][11][12] , as they do not co-occur under natural geological conditions. To date, comparisons between hominin intentional stone flaking and wild primate stone tool use have focused on West African chimpanzees (Pan troglodytes verus) [13][14][15][16] . Nevertheless, stone breakage during chimpanzee tool use is accidental 15 , a result of missed hits or indirect force application during activities such as nut-cracking. The resulting stone fragments lack most of the diagnostic criteria listed above for hominin flakes 10,17 . Even when the manufacture of sharp edges was taught to captive bonobos (Pan paniscus), the resulting flaked assemblage did not replicate the early hominin archaeological record 18 .The capuchins of Serra da Capivara National Park (SCNP) in Brazil use stone tools in more varied activities than any other known non-human primate, including for pounding foods, digging, and in sexual displays [19][20][21] . Bearded capuchins and some Japanese macaques (Macaca fuscata) are known to pound stones directly against each other 22 , however, the SCNP capuchins are the only wild primates that do so for the purpose of damaging those stones 19 . This activity, which we term stone on stone (SoS) percussion, typically involves an individual selecting rounded quartzite cobbles from a conglomerate bed (active hammers), and with one or two hands striking the hammerstone forcefully and repeatedly on quartzite In addition to deliberately crushing the surface of both the active and passive hammers, the capuchins regularly unintentionally break the stones during use (Extended Data 1). In addition, we observed a capuchin purposefully place a newly fractured stone flake on top of another stone, and then strike it with a hammer in a manner resembling chimpanzee nutcracking or human bipolar reduction (Extended Data 1). Nevertheless, while the monkeys were seen to re-use broken hammerstone parts as fresh hammers, they were not observed using the sharp edges of fractured tools to cut or scrape other objects.We collected fragmented stones immediately after capuchins were observed using them at the Oitenta site in SCNP (8º 52.394 S, 42º 37.971 W) (Figure 1), as well as from surface surveys and archaeological excavation in the same area (Extended Data 2). The assemblage consists of 111 capuchin modified stone artefacts, including complete and broken hammerst...

The spontaneous use of stone tools for cracking nuts by tufted capuchin monkeys, now known to be habitual among wild populations in savanna environments, was first described in a semifree group living in the Tietê Ecological Park (SP, Brazil). Nut-cracking at TEP was first observed by our team in 1995 (Ottoni and Mannu in Int J Primatol 22(3):347-358, 2001), and its ontogeny and associated social dynamics, with inexperienced observers highly interested in the activities of proficient individuals, greatly tolerant to scrounging, support hypotheses about social biases on tool-use learning. Here we further analyze the social learning biases, better characterizing: the social context of nut-cracking in which observation by conspecifics occurs, the quality of the nut-cracking behavior itself and whether scrounging may be the motivation behind this behavior. We confirm that the choice of observational targets is an active one; monkeys do not simply observe those who they are socially close to. We investigate social learning strategies, describing how young capuchins choose to observe older, more proficient and dominant individuals during nut-cracking bouts. Monkeys with higher productivity rates were also more frequently targeted by observers, who were tolerated scroungers, further supporting the scrounging hypothesis. Finally, based on changes of the demographic patterns of tool use and observation, we set to retrace data from 14 years of continuous studies. We argue that we have followed the dissemination of the behavior (Transmission Phase) almost from its beginning, when juveniles were the most frequent nutcrackers, to a more common pattern where adults are the most active tool users (Tradition Phase).

The use of pounding stone tools (PSTs) is a customary behaviour in several wild populations of capuchin monkeys; most of these monkeys use PSTs primarily to open hard palm nuts. Here, we describe the use of PSTs in two not previously studied groups of capuchin monkeys (Sapajus libidinosus) in Serra da Capivara National Park (SCNP), northeastern Brazil, and compare them to other groups and populations. Capuchins from SCNP are one of the only known population that habitually use PSTs for several purposes other than nut processing, including cracking seeds and fruits, breaking and/or enlarging holes in tree trunks or rocks, and pulverizing pebbles. Moreover, they use PSTs sequentially with probe stick tools to access hidden prey. The average size of PSTs was larger than the average locally available stones, suggesting active choice. The two groups exhibited more diversity in the use of PSTs than any other known population to date.

Capuchin monkeys (Sapajus spp.) in captive settings frequently manipulate and throw objects. In the wild, they may push or drop stones and sticks toward targets during inter- or intraspecific threat displays. In addition, female capuchin monkeys exhibit a broad repertoire of behaviors during their proceptive period, including facial expressions, vocalizations, stereotyped body postures, and touch-and-run behavior. This study reports stone throwing as a newly-described communicative behavior during the proceptive display of females in a group of bearded capuchin monkeys (S. libidinosus) in Serra da Capivara National Park, Brazil. During a two-year study, three females from one group were seen throwing stones at males during their proceptive phase. After this period, three other females in the same group exhibited the same behavior. Although it may be possible that this pattern is the result of several independent innovations by each female, the apparent absence of this behavior in other groups leads us to suggest that we have documented the diffusion of a new behavioral trait or tradition within this capuchin social group.

No abstract

The human archaeological record changes over time. Finding such change in other animals requires similar evidence, namely, a long-term sequence of material culture. Here, we apply archaeological excavation, dating and analytical techniques to a wild capuchin monkey (Sapajus libidinosus) site in Serra da Capivara National Park, Brazil. We identify monkey stone tools between 2400 and 3000 years old, and based on metric and damage patterns demonstrate that capuchin food processing changed between ~2400 and 300 years ago, and between ~100 years ago and present day. We present the first example of long-term tool-use variation outside of the human lineage and discuss possible mechanisms of extended behavioral change.

Capuchin monkeys at Serra da Capivara National Park (SCNP) usually forage on the ground for roots and fossorial arthropods, digging primarily with their hands but also using stone tools to loosen the soil and aid the digging process. Here we describe the stone tools used for digging by two groups of capuchins on SCNP. Both groups used tools while digging three main food resources: Thiloa glaucocarpa tubers, Ocotea sp roots, and trapdoor spiders. One explanation for the occurrence of tool use in primates is the “necessity hypothesis”, which states that the main function of tool use is to obtain fallback food. We tested for this, but only found a positive correlation between plant food availability and the frequency of stone tools’ use. Thus, our data do not support the fallback food hypothesis for the use of tools to access burrowed resources.

Capuchin monkeys (Sapajus spp.) are proficient tool users, and the use of stone tools occurs in several populations, mostly to crack open encased foods. Two well-studied Brazilian populations of Sapajus libidinosus inhabit Fazenda Boa Vista and Serra da Capivara National Park and present different behavioral sets regarding tool use. Serra das Confusões National Park (SCoNP) lies between those sites, but little is known about the capuchin monkey population that lives there. To begin unraveling the capuchin behavior in this area, we conducted a brief survey for tool use sites. We found indirect evidence that capuchin monkeys at SCoNP use stone hammers to crack open at least four species of seeds and fruits. Plant reproductive parts there are processed with stone tools in a similar pattern to the other sites. Further study is needed to directly observe tool use by capuchin monkeys at SCoNP, verify the occurrence of other possible types of tool use in this population, and thus fully compare their tool use repertoire to that of other populations.