The cultural evolution of early hominins is investigated through the identification of archaeological evidence, primarily in the form of stone artefacts and bones (Leakey, 1971; Schick and Toth, 1994). The emergence and evolution of tool use is generally accepted as a transformational process that led to a suite of adaptations and behaviours, enabling humans to become the most successful primate on the planet (Hovers, 2015). The earliest production of deliberately flaked stone tools dates to ~3.3 Mya (Harmand et al., 2015; Lewis and Harmand, 2016). It has, however, been hypothesized that simple pounding tools may have been a precursor to intentionally flaked technology, potentially originating around or before the period of our last common ancestor with chimpanzees (deBeaune, 2004; Marchant and McGrew, 2005; Rolian and Carvalho, 2017; Thompson et al., 2019).

Although rare, percussive stone tool use is also practiced by a few species of non-human primates. These include Western chimpanzees, Pan troglodytes verus, (Boesch and Boesch, 1990; Sugiyama and Koman, 1979), bearded capuchin monkeys, Sapajus libidinosus, (Fragaszy et al., 2004; Ottoni and Izar, 2008; Falótico and Ottoni, 2016; Luncz et al., 2016a), long-tailed macaques Macaca fascicularis, (Malaivijitnond et al., 2007; Gumert et al., 2009; Luncz et al., 2017a) and one group of white faced capuchin monkeys, Cebus capucinus imitator (Barrett et al., 2018). These non-human primates, similarly to hominins, create long lasting archaeological signatures comprised of lithic assemblages (Mercader et al., 2002; Mercader et al., 2007; Proffitt et al., 2018; Falótico et al., 2019). By merging the fields of archaeology and primatology it is possible to combine direct behavioural observations with the archaeological signature of tool use (Haslam et al., 2009; Rolian and Carvalho, 2017; Carvalho and Almeida-Warren, 2019). Lithic assemblages remain the most abundant source of evidence for understanding early hominin technological and cultural variation (Delagnes and Roche, 2005), as well as social learning (Stout et al., 2019). As such, the field of primate archaeology is well placed to help investigate variation of tool evidence and cultural evolution. Further, this new research field is providing the ability to test various archaeological hypotheses often applied to the Early Stone Age (ESA) archaeological record. Examples of such empirical work include the effect that distance from raw material source has on lithic reduction (Braun et al., 2008a; Luncz et al., 2016b); the effect of population size on resource depletion (Steele and Klein, 2005; Luncz et al., 2017b); and chaine-operatoire approaches to stone tools (Delagnes and Roche, 2005; Carvalho et al., 2008). Archaeological techniques applied to the primate record have also been used to identify evidence of past tool behaviours and expand the temporal signature of tool use in non-human primates (Mercader et al., 2002; Haslam et al., 2016a; Haslam et al., 2016b; Luncz et al., 2016b; Falótico et al., 2019). Furthermore, primate archaeology has proven an effective tool for studying the behaviour of wild non-habituated tool-using populations (Luncz et al., 2017a). Reconstruction of tool selection patterns in wild chimpanzees has for example, repeatedly revealed detailed group-specific behavioural patterns (Koops et al., 2015; Luncz et al., 2015; Pascual-Garrido, 2019). This research provides the ability to quantify behavioural diversity, allowing the identification of cultural variation between distinct populations.

Our close genetic relatedness to great apes has led to intense, decades-long research into the tool behaviour of chimpanzees (McGrew, 2010). More recently, however, attention is being paid to the tool behaviour of monkeys to broaden the comparative context for the evolution and origin of technology. Long-tailed macaques are the only Old-World monkeys who use stone tools in their daily foraging. This behaviour is mainly observed in populations that live along the ocean shores of Southern Thailand and Myanmar where long-tailed macaques use tools primarily to prey on shellfish, including oysters, marine gastropods, crabs and mussels (Gumert et al., 2009), as well as sea almonds (Falótico et al., 2017) and oil palm nuts (Luncz et al., 2017a). Long-tailed macaques, like humans, use stone tools to kill prey and access meat. These foraging behaviours leave distinct damage patterns (use wear) on the hammerstones. Use wear analysis on stone tools combined with direct behavioural observations has been used to associate tool variation with specific prey species (Haslam et al., 2013; Tan et al., 2015; Proffitt et al., 2018). For example, percussive damage on distal pointed ends of the hammerstone has generally been associated with processing rock oysters (Tan et al., 2015), whilst central pitting on a flat hammerstone face is associated with marine snail predation (Gumert et al., 2009; Haslam et al., 2013).

Our recent research published in eLife (Luncz et al., 2017b) focused on providing explanations for observed differences in tool selection between two long-tailed macaque populations. These groups live on neighbouring islands (Koram and Nom Sao Island) on the east coast of Thailand, within the Khao Sam Roi Yot National Park. The results from this study showed that both macaque groups used stone tools to process the same species of shellfish, however the two groups selected different sized stone tools (Luncz et al., 2017b). After comparing underlying ecological factors, potentially affecting this disparity in tool size selection, our data suggested that the differences in tool selection were related to the varying prey sizes on each island. Differences in prey size were associated with overharvesting and resource depletion through increased predation pressure on one island. Maximising foraging efforts, macaques appear to preferentially target larger prey, leading to a reduction in the available prey populations and resulting in an overabundance of smaller, sexually immature prey specimens on the more heavily populated Koram Island, in turn leading to the use of smaller hammerstones. Conversely, on the less populated neighbouring island of Nom Sao, the prey population remained abundant and significantly larger in size, resulting in the use of larger hammerstones.

The tool-assisted feed-back loop observed amongst the macaque population at Khao Sam Roi Yot National Park has interesting hominin archaeological similarities. The earliest repeated shellfish exploitation is known to have occurred in South Africa during the Middle Stone Age (MSA) and Later Stone Age (LSA) (Steele and Klein, 2008). Chronological variations in shellfish sizes found in archaeological middens from the both MSA and LSA have been used as proxies for hominin population increases. Increased shellfish collection during the LSA compared to the MSA (Sealy and Galimberti, 2011) has been used to argue for and against a long and short chronology for the appearance of modern human behaviour (Mcbrearty and Brooks, 2000; Klein, 2008; Steele and Klein, 2005). However, others have also suggested that changing environmental factors may have been a contributing factor in this shellfish size variation (Sealy and Galimberti, 2011). The primate archaeological evidence from Khao Sam Roi Yot provides a direct primate analogy to a phenomenon previously observed through the archaeological record, allowing the ability to directly observe and monitor the effect that population size of tool using primates has on the available shellfish population.

This Research Advance paper builds on and expands our previous research to include further investigation into variation in tool selection and use patterns between long-tailed macaques. By comparing tool selection and use wear patterns between two adjacent islands in the Ao Phang Nga National Park in Southern Thailand we present new information on the possible underlying reasons behind tool variation seen in macaques (Luncz et al., 2017b). This area of investigation is not only important for understanding inter-group primate tool variation, but also allows testing of expectations derived from archaeological theory to understand possible underlying factors associated with stone tool variation in the ESA. These include the cultural historic approach and the use of typological analysis to document and understand variation between hominin lithic assemblages (Leakey, 1971; Isaac, 1977a), the application of a palaeoecological approach, where external environmental factors are seen as important drivers of stone tool variation (Isaac, 1977b; Toth, 1982; Toth, 1985; Braun and Harris, 2003; Braun et al., 2010). And finally, a chaine-operatoire or technological approach, where emphasis is placed on understanding the complete technological production and use of lithic assemblages, with variation seen to some extent as culturally or socially mediated (Delagnes and Roche, 2005; Roche and Texier, 1996; Roche et al., 1999; de la Torre and Mora, 2005).

During exploratory pilot fieldwork on the western side of peninsular Thailand in the Andaman Sea, approximately 500 km southeast of the previous study site in Khao Sam Roi Yot National Park, we identified two island dwelling populations in the Ao Phang Nga National Park, at Boi Yai Island and Lobi Bay (~9 km apart; Figure 1) who routinely use stone tools to process the same marine resources. Initial findings suggested possible inter-group tool use differences and as such a possible variation in the macaque archaeological record.

Figure 1

Download asset Open asset

By focusing on intensity of use wear as a proxy for tool re-use and by accounting for underlying ecological and environmental factors of both Boi Yai Island and Lobi Bay, we aim to suggest possible drivers for the observed stone tool variation between the two populations. If environmental circumstances are similar and the factors influencing tool selection, such as prey size, raw material availability and prey availability do not differ between islands, the possibility that tool use behaviour in long-tailed macaques is socially learned cannot be dismissed.

In total, we analysed 115 stone tools combined from both locations (Table 1).

The stone tool variation of the macaque populations of Boi Yai Island and Lobi Bay are separated into two categories; use wear by prey and size of tools selected by prey. Figure 2 shows examples of the distinct differences of use wear intensity of tools used to process rock oysters (Figure 2B) between Lobi Bay (Figure 2A) and Boi Yai Island (Figure 2C). Similarly, Figure 3 illustrates the profound differences between use wear grading (UWG) ratings for tools used to exploit Thais bitubercularis (Figure 3B) on Lobi Bay (Figure 3A) and Boi Yai Island (Figure 3C).

Figure 2

Download asset Open asset

Figure 3

Download asset Open asset

The comparison between UWG revealed differences between the sites. Stone tools used to crack open oysters are more intensively used on Boi Yai Island compared to Lobi Bay (Figure 4, Mann-Whitney U test: U = 32, N1 = 10, N2 = 26, p<0.001). Similar results can be found for UWG on stone tools used to crack Thais bitubercularis shells (Figure 4, Mann-Whitney U test: U = 1.5, N1 = 9, N2 = 12, p<0.001). The three morphologically similar marine snails (Nerita spp., Monodonta Labio and Morulla spp.) however, produced little in terms of inter-group UWG variation of tool intensity (Figure 4, Mann-Whitney U test: U = 381.5, N1 = 27, N2 = 29, p=0.832).

Figure 4

Download asset Open asset

A comparison of tool size selection associated with prey type revealed differences between Boi Yai Island and Lobi Bay in several important aspects. For marine snails, we found that macaques in Lobi Bay selected heavier tools than on Boi Yai Island (Figure 5A, Linear model: E = −1.100 SE = 0.176 F_(1,54)=38.898 P<0.001). When preying on Thais bitubercularis however, both populations selected similarly sized tools (Figure 5B, Linear model: E = −0.099 SE = 0.194 F_(1,19)=0.263 P=0.614). The size of the available prey was similar at both sites (Figure 6, site comparison C. bifasciatus: Mann-Whitney U test: z = −1.368, N1 = 21, N2 = 73, p=0.086; island comparison marine snails: Mann-Whitney U test: z = −0.511, N1 = 123, N2 = 129, p=0.305, island comparison Thais bitubercularis: Mann-Whitney U test: z = −0.458, N1 = 14, N2 = 88, p=0.324).

Figure 5

Download asset Open asset

Figure 6

Download asset Open asset

Figure 6—source data 1

Maximum length and maximum width of marine snails from Boi Yai Island and Lobi Bay.

https://doi.org/10.7554/eLife.46961.009

Download elife-46961-fig6-data1-v1.xlsx

To exploit oysters, however, macaques on Boi Yai Island used heavier tools than those used for processing the same prey in Lobi Bay (Figure 7, Linear model: E = 0.451 SE = 0.181 F_(1,34)=6.197 P=0.018). Oyster size on Boi Yai Island were, in general, larger than in Lobi Bay (Figure 8, Mann-Whitney U test: z = −2.862, N1 = 341, N2 = 436, p=0.002).

Figure 7

Download asset Open asset

Figure 8

Download asset Open asset

Figure 8—source data 1

Maximum length and maximum width of oysters on Boi Yai Island and Lobi Bay.

https://doi.org/10.7554/eLife.46961.012

Download elife-46961-fig8-data1-v1.xlsx

Several (n = 7) stone tools on Boi Yai Island showed multiple use wear patterns (on the face and on the tip of the tool). Using the methods of Haslam et al. (2013), these damage patterns are indicative of being used on more than one prey species.

Average weight of available raw material (bootstrapped 95% confidence intervals), separated between intertidal and tidal zones differed between sites (Figure 9A, Mann-Whitney U test: z = −5.107, N1 = 270, N2 = 432, p<0.001). The raw material availability also differed between sites (bootstrapped 95% confidence intervals over observed plots) (Mann-Whitney U test: z = −1.911, N1 = 20, N2 = 24, p=0.028). However, when separated by tidal and intertidal zones only, availability on Boi Yai Island shows a trend towards more stones available in the intertidal zone (Figure 9B, Mann-Whitney U test: z = −1.374, N1 = 20, N2 = 23, p=0.085). The availability in the tidal zone is similar at both sites (Figure 9B, Mann-Whitney U test: z = −1.214, N1 = 20, N2 = 24, p=0.112).

Figure 9

Download asset Open asset

Figure 9—source data 1

Measurements and weight of stones available in the tidal and intertidal zone on Boi Yai Island and Lobi Bay.

https://doi.org/10.7554/eLife.46961.014

Download elife-46961-fig9-data1-v1.xlsx

This study explores potential factors behind the variation in percussive stone tool use of two wild macaque populations from adjacent islands in the Ao Phang Nga National Park in Thailand. Macaques on these islands showed differences in their tool selection and degrees of tool reuse when foraging for marine prey. Tool selection was dependent on the species preyed upon. Macaques on Boi Yai Island selected heavier stone tools than those at Lobi Bay to process oysters. Comparisons of available prey species between the sites showed that oysters at Boi Yai Island were indeed larger. The heavier weight of oyster tools used on Boi Yai Island is therefore not surprising and reiterates previous findings, supporting that macaques adjust tool size to prey size (Luncz et al., 2017b; Gumert et al., 2013). Functional fixedness in regard to stone tool behavioural patterns and target foods can be observed across all tool using non-human primates (Carvalho et al., 2008; Fragaszy et al., 2010; Luncz et al., 2016a). For the larger gastropod (Thais bitubercularis) prey, both macaque populations selected similar sized tools to exploit similar sized resources. However, this pattern differs in respect to the processing of marine snails, where the Lobi Bay population selected heavier tools to exploit prey of a similar size to that recorded at Boi Yai Island. Variation in available raw material does not explain the differences in stone tool selection, as the mean weight of available raw material was in fact greater on Boi Yai Island. Furthermore, suitable raw material was available in greater quantities along the shore (especially in the intertidal zone) on Boi Yai Island. Based on this evidence, it is possible to suggest that purely ecological or environmental factors only account for some of the stone tool variation observed between these populations.

When assessing use wear intensity across the two sites, however, additional factors must be explored to explain the apparent variation. Compared to Lobi Bay, the Boi Yai Island tools showed a higher degree of use wear intensity. This pattern was recorded across oyster and Thais bitubercularis tools. The differences in oyster tools are most likely influenced by the oyster size difference reported between the locations. The intensity of use wear seen on oyster tools of Boi Yai Island, however, is unlikely to have developed during a single foraging event (Haslam et al., 2016c). Thais bitubercularis tools used on Boi Yai were characterised by the development of substantial central pits, suggesting multiple re-use events, whilst the hammerstones used to process the same species on Lobi Bay showed few signs of percussive damage. For marine snails (Nerita spp., Monodonta Labio and Morulla spp.), there was no significant difference in use wear intensity. It is reasonable to suggest that the relative fragility of these prey species means that little force was required to open them. Consequently, use wear intensity is low for these tools on both islands.

The lack of evidence of re-used hammerstones on Lobi Bay could be influenced by the tidal forces that potentially remove used tools from their original location. Lobi Bay however, appears relatively sheltered compared to Boi Yai Island as it lies within a large bay. Future research will be able to document the effect of tidal forces on tool movement and will clarify the availability of used tools between populations. A single example of a granite hammerstone was identified within the Boi Yai assemblage (Table 1). This igneous rock is more dense than the available limestone rocks available to the macaques which may have been a factor in its selection and re-use as a hammerstone. Of course, the re-use of this rock may be coincidental, and it should be remembered that any available granite has been geologically transported to Boi Yai Island from elsewhere and is therefore very rare (Luncz et al., 2017a).

As shown previously, raw material availability is consistent between both islands, with limestone constituting most of the available raw material. Scarcity of raw material, cannot, therefore, explain the apparent preference for tool re-use on Boi Yai Island. Indeed, raw material availability on Boi Yai Island is greater than that found at Lobi Bay. This would suggest that macaques on Boi Yai Island, unlike their neighbours, preferentially re-use tools rather than choose from readily available and suitable local stones.

The tool use variation observed between these two island primate populations meets the criteria for tool curation as discussed in the hominin archaeological literature. Shott and Sillitoe (2005) define lithic tool curation as the ‘ratio of realized to maximum utility’ of a tool. The varying degrees of repeated use, shown by use wear assessments of the hammerstones between the two islands, coupled with the similarities in primate species, raw material availability, processed prey species, and local ecological settings, suggest that the macaques on Boi Yai Island are successfully extracting a greater degree of utility from their hammerstones compared to those used on Lobi Bay. These variations in the intensity of tool use suggest a primate example of curated stone tool use on Boi Yai Island compared to those on Lobi Bay.

Previously, tool differences between wild macaque groups were only known to be influenced by prey size (Tan et al., 2015; Luncz et al., 2017b; Gumert and Malaivijitnond, 2013) or sex of the tool user (Gumert et al., 2011). Furthermore, it has been shown that the frequency of tool use in long-tailed macaques might be influenced by genetics, where the Burmese subspecies (Macaca fascicularis aurea) and hybrids expressing a more Burmese phenotype use tools in higher frequencies (Gumert et al., 2019). Our research sites in the Ao Phang Nga National Park lie within a natural hybrid zone and phylogenetic differences between groups cannot yet be fully excluded. Preliminary data show similar degrees of hybridization between groups (Malaivijitnond et al., 2007). The demographics (assessed from video footage, Luncz et al., 2017a) do not differ between the two populations. Males and females of all age classes use stone tools, it therefore seems unlikely that the difference in stone tools between the two islands stem from these factors. Muscle strength, individual proficiency and strike accuracy may all be contributing factors to the development of use wear, as these tools were most likely repeatedly used by multiple individuals over numerous tool use episodes. However, similar demographics between both macaque populations make it unlikely that these factors contributed to the differences found in use wear intensity. Additionally, by combining our new results here with our previous findings of tool use by macaques in the Gulf of Thailand (Luncz et al., 2017b), we were able to identify that macaques of Lobi Bay and Boi Yai Island do not forage on Cerith bifasciatus, despite its widespread abundance. Macaques in the Gulf of Thailand, however, regularly exploit this species.

These results partly support previous research that has shown that tool selection can be explained by ecological, biological and environmental factors (Gumert et al., 2011; Gumert and Malaivijitnond, 2013; Luncz et al., 2017b). However, the differences in use wear intensity and therefore frequency of re-use of hammerstones on Boi Yai Island remains unexplained by these factors.

Our new results show differences in use wear intensity and the extent to which macaques unintentionally modify the shape of their tools through use. This would suggest that tool use across a synchronous landscape need not be uniform, and highlights the potential for the development of synchronic tool use variation within species. Indeed, tool variation may be conditioned by cultural factors as well as responses to ecological conditions. Tool use has been shown to be influenced by social learning in several species (van Schaik et al., 1999; Whiten, 2000). To date, distinct cultural differences in technological behaviour in living primates has mainly been associated with the ape clade (Whiten et al., 1999; Whiten and Boesch, 2001; van Shaik, 2004; Luncz et al., 2012).

As this study, however, is dependent on primate archaeological data, as opposed to direct behavioural observations, it is important to note that its interpretations are subject to the same or similar constraints as found in the early hominin archaeological record. Identifying underlying reasons for behavioural variation in the animal kingdom often requires direct observations of differential tool use despite similar ecological situations between populations. Direct observation of behaviour is, however, impossible when attempting to assess cultural variation in the early archaeological record, and as such a cultural driver for observed lithic variation should only be invoked once non-cultural factors have been ruled out. Non-cultural factors may include, raw material availability and quality, ecological variation, adaptation to climatic change and genetic variation. In the absence of direct observations primate archaeology must also strive for similar goals in identifying possible cultural variation.

The observed artefactual variation between the two island macaque populations described here, although offering an opportunity for investigating the reasons for variation in tool using macaque populations, also provides a unique primate analogy to discuss possible drivers behind early lithic variability in the hominin archaeological record from a similar perspective as that available to archaeologists. Thus, it challenges us to consider the variables in the archaeological record that might drive assemblage composition but cannot be immediately tied to ecological or raw material constraints. Within the field of palaeolithic archaeology, understanding the cultural factors behind lithic variation has been at the forefront of research and has led to two primary theoretical frameworks, the cultural historic approach, which stressed the importance of typological tool categories to develop sequences of hominin cultural traditions (Leakey, 1971; Isaac, 1977a) and the chaine-operatoire approach (Roche and Texier, 1996; Roche et al., 1999; Delagnes and Roche, 2005; de la Torre and Mora, 2005; de la Torre, 2011), which has been used to reconstruct the technical processes and the social acts involved in tool use. At its core, however, is the working assumption that hominin lithic variation is a product of cultural differences both between geographically and temporally distinct groups as well as between hominin species (Sellet, 1993).

The other side of the theoretical divide is an ecological approach to lithic variation. After identifying limitations in the cultural historic approach for understanding the wider effects that the environment and ecology had on hominin behaviour and stone tools a palaeoecological approach has been put forward (Isaac, 1977b; Toth, 1982; Toth, 1985; Braun and Harris, 2003; Braun et al., 2010). This framework stressed the importance of viewing hominin stone tools as being intrinsically linked to external environmental and ecological factors. These included, ecological factors (Braun and Harris, 2003; Braun et al., 2010), raw material availability (Stout et al., 2005; Harmand, 2009; Braun et al., 2008b; Braun et al., 2009a; Braun et al., 2009b; Goldman-Neuman and Hovers, 2012) and functional factors (Toth, 1985).

One of the strengths of primate archaeological studies is the ability to test long standing fundamental archaeological theories and assumptions by applying them to stone tool using living primates (Haslam et al., 2009; Luncz et al., 2016b). Our findings suggest that when raw material availability, species differences, functional differences and environmental and ecological conditions are shared and do not explain stone tool variation the effect of cultural differences as a driving factor behind lithic technological variation in hominins must not be overlooked (Koops et al., 2015; Luncz et al., 2015; Pascual-Garrido, 2019). Our results highlight the possibility that tool selection in old world monkeys might also be affected through social learning and therefore might classify as a cultural behaviour.

This study builds a platform for long-term research focused on the group specific behaviours in populations of long-tailed macaques through the archaeological analysis of tool. Further archaeological research at the site coupled with direct observations will reveal the stepwise development of use wear patterns in long-tailed macaques. This highlights the potential of primate archaeology for answering questions regarding the ecological and socio-cultural factors which affected the development of stone tool use in our own lineage, given the absence of direct observations on early hominins (Westergaard, 1998; Wynn et al., 2011).

Unfortunately, the number of islands where long-tailed macaques are known to use tools are few and, in each instance, the cultural behaviour is possibly unique. The Andaman Sea coast of Thailand is renowned for its natural beauty and attracts increasing numbers of tourists. Increased human contact is known to affect stone tool behaviour by altering natural foraging behaviours (Gumert et al., 2013; Luncz et al., 2017a). Long-tailed macaques are experiencing profound population threats (Eudey, 2008). However, it is clear that these potentially rare, and certainly distinctive, examples of tool behaviour in old world monkeys need to be preserved and protected from human interference. Otherwise examples of extraordinary material culture may be lost before they are even discovered.

All data generated or analysed during this study are included in the manuscript and supporting files.

1. 1. Barrett BJ
   2. Monteza-Moreno CM
   3. Dogandžić T
   4. Zwyns N
   5. Ibáñez A
   6. Crofoot MC

   (2018) Habitual stone-tool-aided extractive foraging in white-faced capuchins, Cebus capucinus

   Royal Society Open Science 5:181002.

   https://doi.org/10.1098/rsos.181002

   • PubMed
   • Google Scholar
2. 1. Boesch C
   2. Boesch H

   (1990) Tool use and tool making in wild chimpanzees

   Folia Primatologica 54:86–99.

   https://doi.org/10.1159/000156428

   • Google Scholar
3. 1. Braun DR
   2. Rogers MJ
   3. Harris JW
   4. Walker SJ

   (2008a) Landscape-scale variation in Hominin tool use: evidence from the developed oldowan

   Journal of Human Evolution 55:1053–1063.

   https://doi.org/10.1016/j.jhevol.2008.05.020

   • PubMed
   • Google Scholar
4. 1. Braun DR
   2. Plummer T
   3. Ditchfield P
   4. Ferraro JV
   5. Maina D
   6. Bishop LC
   7. Potts R

   (2008b) Oldowan behavior and raw material transport: perspectives from the kanjera formation

   Journal of Archaeological Science 35:2329–2345.

   https://doi.org/10.1016/j.jas.2008.03.004

   • Google Scholar
5. 1. Braun DR
   2. Harris JWK
   3. Maina DN

   (2009a) Oldowan raw material procurement and use: evidence from the koobi fora formation

   Archaeometry 51:26–42.

   https://doi.org/10.1111/j.1475-4754.2008.00393.x

   • Google Scholar
6. 1. Braun DR
   2. Plummer T
   3. Ferraro JV
   4. Ditchfield P
   5. Bishop LC

   (2009b) Raw material quality and oldowan hominin toolstone preferences: evidence from kanjera south, Kenya

   Journal of Archaeological Science 36:1605–1614.

   https://doi.org/10.1016/j.jas.2009.03.025

   • Google Scholar
7. 1. Braun DR
   2. Rogers MJ
   3. Harris JW
   4. Walker SJ

   (2010)

   New Perspectives on Old Stones

   167–182, Quantifying variation in landscape-scale behaviors: the Oldowan from Koobi Fora, New Perspectives on Old Stones, New York, Springer.

   • Google Scholar
8. 1. Braun DR
   2. Harris JW

   (2003)

   Technological developments in the oldowan of koobi fora: innovatives techniques of artifact analysis

   Treballs d'Arqueologia 9:117–144.

   • Google Scholar
9. 1. Carvalho S
   2. Cunha E
   3. Sousa C
   4. Matsuzawa T

   (2008) Chaînes opératoires and resource-exploitation strategies in chimpanzee (pan Troglodytes) nut cracking

   Journal of Human Evolution 55:148–163.

   https://doi.org/10.1016/j.jhevol.2008.02.005

   • PubMed
   • Google Scholar
10. Book

    1. Carvalho S
    2. Almeida-Warren K

    (2019)

    Primate archaeology

    In: Choe JC, editors. Encyclopedia of Animal Behavior. Academic Press. pp. 397–407.

    • Google Scholar
11. 1. Charusiri P
    2. Clark AH
    3. Farrar E
    4. Archibald D
    5. Charusiri B

    (1993) Granite belts in Thailand: evidence from the 40ar/39Ar geochronological and geological syntheses

    Journal of Southeast Asian Earth Sciences 8:127–136.

    https://doi.org/10.1016/0743-9547(93)90014-G

    • Google Scholar
12. 1. de la Torre I

    (2011) The Early stone age lithic assemblages of gadeb (Ethiopia) and the developed oldowan/early acheulean in east africa

    Journal of Human Evolution 60:768–812.

    https://doi.org/10.1016/j.jhevol.2011.01.009

    • PubMed
    • Google Scholar
13. Book

    1. de la Torre IA
    2. Mora R

    (2005)

    Technological Strategies in the Lower Pleistocene at Olduvai Beds I and II

    University of Liège Press.

    • Google Scholar
14. 1. deBeaune S

    (2004) The invention of technology: prehistory and cognition

    Current Anthropology 45:139–162.

    https://doi.org/10.1086/381045

    • Google Scholar
15. 1. Delagnes A
    2. Roche H

    (2005) Late pliocene hominid knapping skills: the case of lokalalei 2C, West Turkana, Kenya

    Journal of Human Evolution 48:435–472.

    https://doi.org/10.1016/j.jhevol.2004.12.005

    • PubMed
    • Google Scholar
16. 1. Eudey AA

    (2008) The Crab-Eating macaque (Macaca fascicularis): Widespread and rapidly declining

    Primate Conservation 23:129–132.

    https://doi.org/10.1896/052.023.0115

    • Google Scholar
17. 1. Falótico T
    2. Spagnoletti N
    3. Haslam M
    4. Luncz LV
    5. Malaivijitnond S
    6. Gumert M

    (2017) Analysis of sea almond ( Terminalia catappa ) cracking sites used by wild Burmese long-tailed macaques ( Macaca fascicularis aurea )

    American Journal of Primatology 79:e22629.

    https://doi.org/10.1002/ajp.22629

    • Google Scholar
18. 1. Falótico T
    2. Proffitt T
    3. Ottoni EB
    4. Staff RA
    5. Haslam M

    (2019) Three thousand years of wild capuchin stone tool use

    Nature Ecology & Evolution 3:1034–1038.

    https://doi.org/10.1038/s41559-019-0904-4

    • PubMed
    • Google Scholar
19. 1. Falótico T
    2. Ottoni EB

    (2016) The manifold use of pounding stone tools by wild capuchin monkeys of serra da Capivara National Park, Brazil

    Behaviour 153:421–442.

    https://doi.org/10.1163/1568539X-00003357

    • Google Scholar
20. 1. Fragaszy D
    2. Izar P
    3. Visalberghi E
    4. Ottoni EB
    5. de Oliveira MG

    (2004) Wild capuchin monkeys (Cebus libidinosus) use anvils and stone pounding tools

    American Journal of Primatology 64:359–366.

    https://doi.org/10.1002/ajp.20085

    • PubMed
    • Google Scholar
21. 1. Fragaszy DM
    2. Greenberg R
    3. Visalberghi E
    4. Ottoni EB
    5. Izar P
    6. Liu Q

    (2010) How wild bearded capuchin monkeys select stones and nuts to minimize the number of strikes per nut cracked

    Animal Behaviour 80:205–214.

    https://doi.org/10.1016/j.anbehav.2010.04.018

    • Google Scholar
22. 1. Goldman-Neuman T
    2. Hovers E

    (2012) Raw material selectivity in late pliocene oldowan sites in the Makaamitalu Basin, Hadar, Ethiopia

    Journal of Human Evolution 62:353–366.

    https://doi.org/10.1016/j.jhevol.2011.05.006

    • PubMed
    • Google Scholar
23. 1. Gumert MD
    2. Kluck M
    3. Malaivijitnond S

    (2009) The physical characteristics and usage patterns of stone axe and pounding hammers used by long-tailed macaques in the andaman sea region of Thailand

    American Journal of Primatology 71:594–608.

    https://doi.org/10.1002/ajp.20694

    • PubMed
    • Google Scholar
24. 1. Gumert MD
    2. Hoong LK
    3. Malaivijitnond S

    (2011) Sex differences in the stone tool-use behavior of a wild population of burmese long-tailed macaques (Macaca fascicularis aurea)

    American Journal of Primatology 73:1239–1249.

    https://doi.org/10.1002/ajp.20996

    • PubMed
    • Google Scholar
25. 1. Gumert MD
    2. Hamada Y
    3. Malaivijitnond S

    (2013) Human activity negatively affects stone tool-using Burmese long-tailed macaques Macaca fascicularis aurea in Laem Son National Park, Thailand

    Oryx 47:535–543.

    https://doi.org/10.1017/S0030605312000130

    • Google Scholar
26. 1. Gumert MD
    2. Tan AWY
    3. Luncz LV
    4. Chua CT
    5. Kulik L
    6. Switzer AD
    7. Haslam M
    8. Iriki A
    9. Malaivijitnond S

    (2019) Prevalence of tool behaviour is associated with pelage phenotype in Intraspecific hybrid long-tailed macaques (Macaca fascicularis aurea × M. f. fascicularis)

    Behaviour 156:1083–1125.

    https://doi.org/10.1163/1568539X-00003557

    • Google Scholar
27. 1. Gumert MD
    2. Malaivijitnond S

    (2013) Long-tailed macaques select mass of stone tools according to food type

    Philosophical Transactions of the Royal Society B: Biological Sciences 368:20120413.

    https://doi.org/10.1098/rstb.2012.0413

    • Google Scholar
28. Book

    1. Harmand S

    (2009)

    Variability in raw material selectivity at the late Pliocene sites of Lokalalei

    In: Hovers E, Braun DR, editors. Interdisciplinary Approaches to the Oldowan. Springer. pp. 85–97.

    • Google Scholar
29. 1. Harmand S
    2. Lewis JE
    3. Feibel CS
    4. Lepre CJ
    5. Prat S
    6. Lenoble A
    7. Boës X
    8. Quinn RL
    9. Brenet M
    10. Arroyo A
    11. Taylor N
    12. Clément S
    13. Daver G
    14. Brugal JP
    15. Leakey L
    16. Mortlock RA
    17. Wright JD
    18. Lokorodi S
    19. Kirwa C
    20. Kent DV
    21. Roche H

    (2015) 3.3-million-year-old stone tools from lomekwi 3, West Turkana, Kenya

    Nature 521:310–315.

    https://doi.org/10.1038/nature14464

    • PubMed
    • Google Scholar
30. 1. Haslam M
    2. Hernandez-Aguilar A
    3. Ling V
    4. Carvalho S
    5. de la Torre I
    6. DeStefano A
    7. Du A
    8. Hardy B
    9. Harris J
    10. Marchant L
    11. Matsuzawa T
    12. McGrew W
    13. Mercader J
    14. Mora R
    15. Petraglia M
    16. Roche H
    17. Visalberghi E
    18. Warren R

    (2009) Primate archaeology

    Nature 460:339–344.

    https://doi.org/10.1038/nature08188

    • PubMed
    • Google Scholar
31. 1. Haslam M
    2. Gumert MD
    3. Biro D
    4. Carvalho S
    5. Malaivijitnond S

    (2013) Use-wear patterns on wild macaque stone tools reveal their behavioural history

    PLOS ONE 8:e72872.

    https://doi.org/10.1371/journal.pone.0072872

    • PubMed
    • Google Scholar
32. 1. Haslam M
    2. Luncz L
    3. Pascual-Garrido A
    4. Falótico T
    5. Malaivijitnond S
    6. Gumert M

    (2016a) Archaeological excavation of wild macaque stone tools

    Journal of Human Evolution 96:134–138.

    https://doi.org/10.1016/j.jhevol.2016.05.002

    • PubMed
    • Google Scholar
33. 1. Haslam M
    2. Luncz LV
    3. Staff RA
    4. Bradshaw F
    5. Ottoni EB
    6. Falótico T

    (2016b) Pre-Columbian monkey tools

    Current Biology 26:R521–R522.

    https://doi.org/10.1016/j.cub.2016.05.046

    • PubMed
    • Google Scholar
34. 1. Haslam M
    2. Pascual-Garrido A
    3. Malaivijitnond S
    4. Gumert M

    (2016c) Stone tool transport by wild burmese long-tailed macaques ( Macaca fascicularis aurea )

    Journal of Archaeological Science: Reports 7:408–413.

    https://doi.org/10.1016/j.jasrep.2016.05.040

    • Google Scholar
35. 1. Hovers E

    (2015) Archaeology: tools go back in time

    Nature 521:294–295.

    https://doi.org/10.1038/521294a

    • PubMed
    • Google Scholar
36. Book

    1. Isaac GL

    (1977a)

    Olorgesailie: Archaeological Studies of a Middle Pleistocene Lake Basin

    Chicago: University of Chicago Press.

    • Google Scholar
37. Book

    1. Isaac GL

    (1977b)

    Squeezing Blood From Stones. Stone Tools as Cultural Markers: Change, Evolution, and Complexity

    New Jersey: Humanities Press.

    • Google Scholar
38. 1. Klein RG

    (2008) Out of Africa and the evolution of human behavior

    Evolutionary Anthropology: Issues, News, and Reviews 17:267–281.

    https://doi.org/10.1002/evan.20181

    • Google Scholar
39. 1. Kongapai P
    2. Sompongchaiyakul P
    3. Jitpraphai S
    4. Gerald Plumley F

    (2016) Beach forest changes (2003–2013) in the tsunami-affected area of Phang Nga, Thailand from multi-temporal satellite data

    ScienceAsia 42:159–170.

    https://doi.org/10.2306/scienceasia1513-1874.2016.42.159

    • Google Scholar
40. 1. Koops K
    2. Schöning C
    3. Isaji M
    4. Hashimoto C

    (2015) Cultural differences in ant-dipping tool length between neighbouring chimpanzee communities at Kalinzu, Uganda

    Scientific Reports 5:12456.

    https://doi.org/10.1038/srep12456

    • PubMed
    • Google Scholar
41. Book

    1. Kuttikul P

    (2015)

    The Invaluable Natural Heritage: Thai Geological Site

    Bangkok: Department of Mineral Resources.

    • Google Scholar
42. Book

    1. Leakey MD

    (1971)

    Olduvai Gorge: Volume 3, Excavations in Beds I and II, 1960-1963

    Cambridge University Press.

    • Google Scholar
43. 1. Lewis JE
    2. Harmand S

    (2016) An earlier origin for stone tool making: implications for cognitive evolution and the transition to Homo

    Philosophical Transactions of the Royal Society B: Biological Sciences 371:20150233.

    https://doi.org/10.1098/rstb.2015.0233

    • Google Scholar
44. 1. Luncz LV
    2. Mundry R
    3. Boesch C

    (2012) Evidence for cultural differences between neighboring chimpanzee communities

    Current Biology 22:922–926.

    https://doi.org/10.1016/j.cub.2012.03.031

    • PubMed
    • Google Scholar
45. 1. Luncz LV
    2. Wittig RM
    3. Boesch C

    (2015) Primate archaeology reveals cultural transmission in wild chimpanzees (pan Troglodytes verus)

    Philosophical Transactions of the Royal Society B: Biological Sciences 370:20140348.

    https://doi.org/10.1098/rstb.2014.0348

    • PubMed
    • Google Scholar
46. 1. Luncz LV
    2. Falótico T
    3. Pascual-Garrido A
    4. Corat C
    5. Mosley H
    6. Haslam M

    (2016a) Wild capuchin monkeys adjust stone tools according to changing nut properties

    Scientific Reports 6:33089.

    https://doi.org/10.1038/srep33089

    • PubMed
    • Google Scholar
47. 1. Luncz LV
    2. Proffitt T
    3. Kulik L
    4. Haslam M
    5. Wittig RM

    (2016b) Distance-decay effect in stone tool transport by wild chimpanzees

    Proceedings of the Royal Society B: Biological Sciences 283:20161607.

    https://doi.org/10.1098/rspb.2016.1607

    • Google Scholar
48. 1. Luncz LV
    2. Svensson MS
    3. Haslam M
    4. Malaivijitnond S
    5. Proffitt T
    6. Gumert M

    (2017a) Technological response of wild macaques (Macaca fascicularis) to Anthropogenic Change

    International Journal of Primatology 38:872–880.

    https://doi.org/10.1007/s10764-017-9985-6

    • PubMed
    • Google Scholar
49. 1. Luncz LV
    2. Tan A
    3. Haslam M
    4. Kulik L
    5. Proffitt T
    6. Malaivijitnond S
    7. Gumert M

    (2017b) Resource depletion through primate stone technology

    eLife 6:e23647.

    https://doi.org/10.7554/eLife.23647

    • PubMed
    • Google Scholar
50. 1. Malaivijitnond S
    2. Lekprayoon C
    3. Tandavanittj N
    4. Panha S
    5. Cheewatham C
    6. Hamada Y

    (2007) Stone-tool usage by thai long-tailed macaques (Macaca fascicularis)

    American Journal of Primatology 69:227–233.

    https://doi.org/10.1002/ajp.20342

    • PubMed
    • Google Scholar
51. 1. Marchant LF
    2. McGrew WC

    (2005)

    Stone Knapping the Necessary Conditions for an Uniquely Hominin Behaviour

    341–350, Percussive technology: chimpanzee baobab smashing and the evolutionary modeling of hominid knapping, Stone Knapping the Necessary Conditions for an Uniquely Hominin Behaviour, McDonald Institute Monograph.

    • Google Scholar
52. 1. Mcbrearty S
    2. Brooks AS

    (2000) The revolution that wasn't: a new interpretation of the origin of modern human behavior

    Journal of Human Evolution 39:453–563.

    https://doi.org/10.1006/jhev.2000.0435

    • PubMed
    • Google Scholar
53. 1. McGrew WC

    (2010) Chimpanzee technology

    Science 328:579–580.

    https://doi.org/10.1126/science.1187921

    • Google Scholar
54. 1. Mercader J
    2. Panger M
    3. Boesch C

    (2002) Excavation of a chimpanzee stone tool site in the african rainforest

    Science 296:1452–1455.

    https://doi.org/10.1126/science.1070268

    • PubMed
    • Google Scholar
55. 1. Mercader J
    2. Barton H
    3. Gillespie J
    4. Harris J
    5. Kuhn S
    6. Tyler R
    7. Boesch C

    (2007) 4,300-year-old chimpanzee sites and the origins of percussive stone technology

    PNAS 104:3043–3048.

    https://doi.org/10.1073/pnas.0607909104

    • PubMed
    • Google Scholar
56. 1. Ottoni EB
    2. Izar P

    (2008) Capuchin monkey tool use: overview and implications

    Evolutionary Anthropology: Issues, News, and Reviews 17:171–178.

    https://doi.org/10.1002/evan.20185

    • Google Scholar
57. 1. Pascual-Garrido A

    (2019) Cultural variation between neighbouring communities of chimpanzees at Gombe, Tanzania

    Scientific Reports 9:8260.

    https://doi.org/10.1038/s41598-019-44703-4

    • PubMed
    • Google Scholar
58. 1. Proffitt T
    2. Luncz VL
    3. Malaivijitnond S
    4. Gumert M
    5. Svensson MS
    6. Haslam M

    (2018) Analysis of wild macaque stone tools used to crack oil palm nuts

    Royal Society Open Science 5:171904.

    https://doi.org/10.1098/rsos.171904

    • PubMed
    • Google Scholar
59. Software

    1. R Development Core Team

    (2015) R: A language and environment for statistical computing

    R Foundation for Statistical Computing, Vienna, Austria.

    http://www.r-project.org
60. 1. Roche H
    2. Delagnes A
    3. Brugal JP
    4. Feibel C
    5. Kibunjia M
    6. Mourre V
    7. Texier PJ

    (1999) Early hominid stone tool production and technical skill 2.34 myr ago in West Turkana, Kenya

    Nature 399:57–60.

    https://doi.org/10.1038/19959

    • PubMed
    • Google Scholar
61. Book

    1. Roche H
    2. Texier P-J

    (1996)

    Evaluation of technical competence of Homo erectus in East Africa during the Middle Pleistocene

    In: Bower JRF, Sartorno S, editors. Royal Netherlands Academy of Arts and Sciences. Leiden: Human Evolution in its Ecological Context. pp. 153–167.

    • Google Scholar
62. Book

    1. Rolian C
    2. Carvalho S

    (2017)

    Tool use and manufacture in the last common ancestor of Pan and Homo

    In: Muller MN, Wrangham RW, Pilbeam DR, editors. Chimpanzees and Human Evolution. Massachusetts: Belknap Press. pp. 602–644.

    • Google Scholar
63. Book

    1. Schick K
    2. Toth N

    (1994)

    Making Silent Stones Speak: Human Evolution and the Dawn of Technology

    Simon and Schuster.

    • Google Scholar
64. 1. Sealy J
    2. Galimberti M

    (2011)

    Trekking the Shore

    Shellfishing and the interpretation of shellfish sizes in the Middle and Later Stone Ages of South Africa’, Trekking the Shore, New York, Springer.

    • Google Scholar
65. 1. Sellet F

    (1993) Chaine operatoire; The concept and its applications

    Lithic Technology 18:106–112.

    https://doi.org/10.1080/01977261.1993.11720900

    • Google Scholar
66. 1. Shott MJ
    2. Sillitoe P

    (2005) Use life and curation in New Guinea experimental used flakes

    Journal of Archaeological Science 32:653–663.

    https://doi.org/10.1016/j.jas.2004.11.012

    • Google Scholar
67. 1. Steele TE
    2. Klein RG

    (2005)

    Mollusk and tortoise size as proxies for stone age population density in South Africa: implications for the evolution of human cultural capacity

    Munibe Antropologia-Arkeologia 57:221–237.

    • Google Scholar
68. 1. Steele TE
    2. Klein RG

    (2008)

    Intertidal shellfish use during the middle and later stone age of South Africa

    Archaeofauna 17:63–76.

    • Google Scholar
69. 1. Stout D
    2. Quade J
    3. Semaw S
    4. Rogers MJ
    5. Levin NE

    (2005) Raw material selectivity of the earliest stone toolmakers at Gona, afar, Ethiopia

    Journal of Human Evolution 48:365–380.

    https://doi.org/10.1016/j.jhevol.2004.10.006

    • Google Scholar
70. 1. Stout D
    2. Rogers MJ
    3. Jaeggi AV
    4. Semaw S

    (2019) Archaeology and the origins of human cumulative culture: a case study from the earliest oldowan at Gona, Ethiopia

    Current Anthropology 60:309–340.

    https://doi.org/10.1086/703173

    • Google Scholar
71. 1. Sugiyama Y
    2. Koman J

    (1979) Tool-using and -making behavior in wild chimpanzees at Bossou, guinea

    Primates 20:513–524.

    https://doi.org/10.1007/BF02373433

    • Google Scholar
72. 1. Tan A
    2. Tan SH
    3. Vyas D
    4. Malaivijitnond S
    5. Gumert MD

    (2015) There is more than one way to crack an oyster: identifying variation in burmese Long-Tailed macaque (Macaca fascicularis aurea) Stone-Tool Use

    PLOS ONE 10:e0124733.

    https://doi.org/10.1371/journal.pone.0124733

    • PubMed
    • Google Scholar
73. 1. Thompson JC
    2. Carvalho S
    3. Marean CW
    4. Alemseged Z

    (2019) Origins of the human predatory pattern: the transition to Large-Animal exploitation by early hominins

    Current Anthropology 60:1–23.

    https://doi.org/10.1086/701477

    • Google Scholar
74. Book

    1. Toth NP

    (1982)

    The Stone Technologies of Early Hominids at Koobi Fora, Kenya: An Experimental Approach’

    Berkeley: University of California.

    • Google Scholar
75. 1. Toth N

    (1985) The oldowan reassessed: a close look at early stone artifacts

    Journal of Archaeological Science 12:101–120.

    https://doi.org/10.1016/0305-4403(85)90056-1

    • Google Scholar
76. 1. van Schaik CP
    2. Deaner RO
    3. Merrill MY

    (1999) The conditions for tool use in primates: implications for the evolution of material culture

    Journal of Human Evolution 36:719–741.

    https://doi.org/10.1006/jhev.1999.0304

    • PubMed
    • Google Scholar
77. Book

    1. van Shaik C

    (2004)

    Among Orangutans: Red Apes and the Rise of Human Culture

    Harvard University Press.

    • Google Scholar
78. 1. Westergaard GC

    (1998) What capuchin monkeys can tell Us about the origins of hominid material culture

    Journal of Material Culture 3:5–19.

    https://doi.org/10.1177/135918359800300101

    • Google Scholar
79. 1. Whiten A
    2. Goodall J
    3. McGrew WC
    4. Nishida T
    5. Reynolds V
    6. Sugiyama Y
    7. Tutin CE
    8. Wrangham RW
    9. Boesch C

    (1999) Cultures in chimpanzees

    Nature 399:682–685.

    https://doi.org/10.1038/21415

    • PubMed
    • Google Scholar
80. 1. Whiten A

    (2000) Primate culture and social learning

    Cognitive Science 24:477–508.

    https://doi.org/10.1207/s15516709cog2403_6

    • Google Scholar
81. 1. Whiten A
    2. Boesch C

    (2001) The cultures of chimpanzees

    Scientific American 284:60–67.

    https://doi.org/10.1038/scientificamerican0101-60

    • Google Scholar
82. 1. Wynn T
    2. Hernandez-Aguilar RA
    3. Marchant LF
    4. McGrew WC

    (2011) "An ape's view of the Oldowan" revisited

    Evolutionary Anthropology: Issues, News, and Reviews 20:181–197.

    https://doi.org/10.1002/evan.20323

    • PubMed
    • Google Scholar

Author details

1. Lydia V Luncz

   Primate Models for Behavioural Evolution Lab, University of Oxford, Oxford, United Kingdom

   Contribution

   Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Writing—original draft, Project administration, Writing—review and editing

   For correspondence

   Lydia.Luncz@anthro.ox.ac.uk

   Competing interests

   No competing interests declared

   "This ORCID iD identifies the author of this article:" 0000-0003-2972-4742

2. Mike Gill

   Primate Models for Behavioural Evolution Lab, University of Oxford, Oxford, United Kingdom

   Contribution

   Data curation, Writing—original draft

   Competing interests

   No competing interests declared

3. Tomos Proffitt

   The Institute of Archaeology, University College London, London, United Kingdom

   Contribution

   Investigation, Visualization, Methodology, Writing—original draft, Writing—review and editing

   Competing interests

   No competing interests declared

4. Magdalena S Svensson

   Department of Social Sciences, Oxford Brookes University, Oxford, United Kingdom

   Contribution

   Data curation, Writing—review and editing

   Competing interests

   No competing interests declared

5. Lars Kulik

   Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany

   Contribution

   Investigation, Methodology, Writing—original draft, Writing—review and editing

   Competing interests

   No competing interests declared

6. Suchinda Malaivijitnond

   1. Faculty of Science, Chulalongkorn University, Bangkok, Thailand
   2. National Primate Research Centre of Thailand, Chulalongkorn University, Saraburi, Thailand

   Contribution

   Conceptualization, Project administration, Writing—review and editing

   Competing interests

   No competing interests declared

• 2,083

  views

• 252

  downloads

• 19

  citations

Views, downloads and citations are aggregated across all versions of this paper published by eLife.