Wild monkeys flake stone tools

Abstract

Our understanding of the emergence of technology shapes how we view the origins of humanity. Sharp-edged stone flakes, struck from larger cores, are the primary evidence for the earliest stone technology. Here we show that wild bearded capuchin monkeys (Sapajus libidinosus) in Brazil deliberately break stones, unintentionally producing recurrent, conchoidally fractured, sharp-edged flakes and cores that have the characteristics and morphology of intentionally produced hominin tools. The production of archaeologically visible cores and flakes is therefore no longer unique to the human lineage, providing a comparative perspective on the emergence of lithic technology. This discovery adds an additional dimension to interpretations of the human Palaeolithic record, the possible function of early stone tools, and the cognitive requirements for the emergence of stone flaking.

Full text

00 MONTH 2016 | VOL 000 | NATURE | 1
LETTER doi:10.1038/nature20112
Wild monkeys flake stone tools
Tomos Proffitt1*, Lydia V. Luncz1*, Tiago Falótico2, Eduardo B. Ottoni2, Ignacio de la Torre3 & Michael Haslam1
Our understanding of the emergence of technology shapes how
we view the origins of humanity1,2. Sharp-edged stone flakes,
struck from larger cores, are the primary evidence for the earliest
stone technology3. Here we show that wild bearded capuchin
monkeys (Sapajus libidinosus) in Brazil deliberately break stones,
unintentionally producing recurrent, conchoidally fractured,
sharp-edged flakes and cores that have the characteristics and
morphology of intentionally produced hominin tools. The
production of archaeologically visible cores and flakes is therefore
no longer unique to the human lineage, providing a comparative
perspective on the emergence of lithic technology. This discovery
adds an additional dimension to interpretations of the human
Palaeolithic record, the possible function of early stone tools,
and the cognitive requirements for the emergence of stone
flaking.
Palaeoanthropologists 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 them4.
Suggested hallmarks of the earliest stone tool technology include
(i) controlled, conchoidal flaking5;(ii) production of sharp cutting
edges6; (iii) repeated removal of multiple flakes from a single core;
(iv) clear targeting of core edges; and (v) adoption of specific flaking
patterns7. These characteristics underlie the identification of intentional
stone flaking at all early archaeological sites3,5,7–12, 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)
13–16
. 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 flakes10,17. 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
displays19–21. Bearded capuchins and some Japanese macaques (Macaca
fuscata) are known to pound stones directly against each other22, but
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 hammer-stone forcefully and
repeatedly on quartzite cobbles embedded within the conglomerate
(passive hammers) (Fig. 1, Supplementary Video 1).
Previous observations of capuchin stone percussion indicate that
this behaviour occurs in an aggressive context23. In our observations,
however, the monkeys licked or sniffed the crushed passive hammers
in about half of the SoS percussion events19 (Supplementary Video 1),
suggesting that they may be ingesting either powdered quartz or lichens.
While the stones do not contain any biologically active components19,
silicon is known to be an essential trace nutrient24. SCNP capuchins
have also been seen to use a stone hammer to dislodge another stone
from the conglomerate, with the second stone then used as a hammer
for SoS percussion20.
As well as deliberately crushing the surface of both the active and
passive hammers, the capuchins regularly unintentionally fracture the
stones during use (Supplementary Video 1). In addition, we observed
a capuchin place a newly fractured stone flake on top of another stone,
and then strike it with a hammer in a manner resembling chimpanzee
nut-cracking or human bipolar reduction (Supplementary Video 1).
Nevertheless, while the monkeys were seen to re-use broken
hammer-stone 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 (8° 52.394′ S,
42° 37.971′ W) (Fig. 1), as well as from surface surveys and archaeolo-
gical excavation in the same area (Extended Data Fig. 1). The assemblage
consists of 111 capuchin-modified stone artefacts, including complete
1Primate Archaeology Research Group, School of Archaeology, University of Oxford, Dyson Perrins Building, South Parks Road, Oxford OX1 3QY, UK. 2Institute of Psychology, University of São
Paulo, São Paulo, SP 05508-030, Brazil. 3Institute of Archaeology, University College London, 31–34 Gordon Square, London WC1H 0PY, UK.
*These authors contributed equally to this work.
Figure 1 | Wild bearded capuchin SoS percussion, Serra da Capivara
National Park, Brazil. a, The conglomerate outcrop where SoS percussive
behaviour of b and c was observed. b, c, SoS percussive actions including
close observation by a juvenile capuchin (b), and stone breakage (c).
Note that the active hammer in use is part of Refit Set 6 (Supplementary
Information and Supplementary Video 1).
bc
a
© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

2 | NATURE | VOL 000 | 00 MONTH 2016
LETTER
RESEARCH
and broken hammer-stones, complete and fragmented flakes, and
passive hammers. We also found flaked hammer-stones, which using
a traditional classification would be considered flaked artefacts25
(Extended Data Table 1). All stones were originally obtained by the
capuchins from conglomerates in the vicinity of their use.
Complete hammer-stones have a mean weight of 600.3 g (Extended
Data Table 2a). They possess varying degrees of percussive damage
across their surfaces, including small impact points surrounded by
circular or crescent scars (Supplementary Information and Extended
Data Fig. 2). Broken hammer-stones and flaked hammer-stones
comprise over a quarter of the total assemblage. Broken hammer-stones
are on average smaller than complete hammer-stones (mean = 203.8 g;
Extended Data Table 2a), and some would be termed split cobbles in
a hominin assemblage. Flaked hammer-stones exhibit one or more
conchoidal or wedge flake scars, occurring either as 1–2 fortuitous
scars from a natural striking platform, or as recurring unidirectional,
overlapping flakes resulting from repeated strikes on a fracture plane
(Fig. 2, Supplementary Information and Extended Data Fig. 3). Refitted
hammer-stones demonstrate this reduction sequence (Supplementary
Information and Extended Data Figs 4, 5). Continuous rotation and
manipulation of the hammer-stones during use also produces small
(< 1 cm), non-invasive, step-terminating flake scars along the edge
of the striking platform, perpendicular to the flaking surface. These
artefacts are indistinguishable from some archaeological examples
of intentionally flaked early hominin stone cores. Using a traditional
classification, the flaked hammer-stones fall within the morphology
of unifacial choppers1.
Complete flakes produced during SoS percussion have sharp edges,
bulbs of percussion and scars from up to three previous flake removals
(Fig. 2, Supplementary Information and Extended Data Fig. 6).
A high proportion of wedge-initiated flakes occur in the early
stages of reduction, evidenced by an increased frequency of cortical
Figure 2 | Examples of flaked stones from capuchin SoS percussion.
a, Detail of a large, unidirectionally flaked active hammer-stone, with
clear impact marks located towards the centre of the striking platform.
b, Refitted active hammer illustrating recurrent unidirectional removal of
at least seven flakes (Refit Set 6; Extended Data Fig. 6b and Supplementary
Video 2). c, e, Examples of conchoidal flakes. Artefact illustrations in e
reproduced with permission from A. Theodoropoulou. d, f, Examples of
flaked hammer-stones. a–f, Scale bars are 5 cm, except for the scale bar in
the inset (a), which is 2 mm.
ab
cd
ef
12
3
3
12
2 mm
© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

00 MONTH 2016 | VOL 000 | NATURE | 3
LETTER RESEARCH
flakes. Conchoidal flakes, on the other hand, come from both early
and later stages of reduction, with both cortical and non- cortical
pieces represented. Extensive refits record the production of unidi-
rectional recurrent, conchoidal flakes following an initial forceful
fracture (Extended Data Figs 5, 6, Supplementary Information and
Supplementary Video 2).
Passive hammers, whether found detached from or embedded in
the conglomerate, typically have a localized area of percussive damage
located on a prominent surface (Fig. 3). The damage includes impact
points, battering marks and crushed quartz crystals and, in some
cases, detached flakes or chips. The passive hammers in this study
(mean = 303.7 g, Extended Data Table 2a) also retain evidence of their
subsequent re-use as active hammers, with impact points located on
previously embedded flat planes opposite the passive hammer damage.
This use clearly occurred after the stone was dislodged from the
conglomerate. Capuchin SoS tools are therefore multifunctional,
with the monkeys able to repurpose stones from a passive to an active
percussive role (Supplementary Information).
The distinctive assemblages found at SoS percussion sites will guide
future archaeological investigations into the development of capuchin
technology at SCNP26, and the broader Middle Pleistocene dispersal of
Sapajus into northeast Brazil
27
. They should also assist in distinguishing
human tools from capuchin artefacts where the ranges of these primates
overlap12. Of interest beyond Sapajus behavioural evolution, SCNP
capuchins produce stone debris through a similar technique (passive
hammer) to that inferred from some of the earliest hominin archae-
ological assemblages3,11. The passive hammer knapping technique
involves striking a hammer-stone onto a passive anvil, with the desired
flakes detached from the hand-held stone
11
(Supplementary Video 1).
Both active and passive hominin hammers often have repeated
impact marks away from the tool’s edge, interpreted as evidence of
poorly controlled strikes or multi-purpose tool use
3
. SCNP capuchin
behaviour demonstrates that these marks and recurrent conchoidally
fractured, sharp-edged flakes, can be produced entirely unintentionally.
The SCNP data provide an example of repeated conchoidal flaking
that is not reliant on advanced, human-like hand morphologies and
coordination28. Similarly, SoS behaviour presents an alternative to
evolutionary explanations that link the origins of recurrent flake
production to a change in hominin cognitive skills28,29. In the absence
of supporting evidence such as cut-marked bones, we suggest that
sharp-edged flake production can no longer be implicitly or solely
associated with intentional production of cutting flakes. Capuchin
SoS percussion and simple Pliocene–Pleistocene stone knapping
activities are equifinal behaviours in the production of flaked lithic
assemblages. These findings open up the possibility that unintentional
flaked assemblages may be identified in the palaeontological record of
extinct apes and monkeys. In light of this possibility, criteria commonly
used to distinguish intentional hominin lithic assemblages need to
be refined.
No living primate is a direct substitute for extinct hominins,
which varied in unknown ways from the behaviour, cognition and
morphology seen in extant animals and humans15. However, capuchin
SoS percussion is an example of intentional stone breakage by a
non-human primate that produces concentrated lithic accumulations.
Capuchin SoS percussion flakes and flaked hammer-stones fall within
the range of mean dimensions for simple flakes and cores from the
Early Stone Age3 (Supplementary Information and Extended Data
Table 2b). If encountered in a hominin archaeological context, this
material would be identified as artefactual, potentially interpreted as
the result of intentional stone fracture and controlled flake production,
and probably attributed to functional needs requiring the use of
sharp edges.
The capuchin data add support to an ongoing paradigm shift in our
understanding of stone tool production and the uniqueness of hominin
technology. Within the last decade, studies have shown that the use
30
and intentional production
3
of sharp-edged flakes is not necessarily
tied to the genus Homo. Capuchin SoS percussion goes a step further,
demonstrating that the production of archaeologically identifiable
flakes and cores, as currently defined, is no longer unique to the human
lineage.
Online Content Methods, along with any additional Extended Data display items and
Source Data, are available in the online version of the paper; references unique to
these sections appear only in the online paper.
Received 15 June; accepted 21 September 2016.
Published online 19 October 2016.
1. Leakey, M. D. Olduvai Gorge, Vol. 3. Excavations in Beds I and II, 1960–1963.
(Cambridge University Press, 1971).
2. Potts, R. Early hominid activities at Olduvai. (AldineTransaction, 1988).
3. Harmand, S. et al. 3.3-million-year-old stone tools from Lomekwi 3, West
Turkana, Kenya. Nature 521, 310–315 (2015).
4. Panger, M. A., Brooks, A. S., Richmond, B. G. & Wood, B. Older than the
Oldowan? Rethinking the emergence of hominin tool use. Evol. Anthr. 11,
235–245 (2002).
5. Isaac, G. L. I. Early hominids in action: a commentary on the contribution of
archaeology to understand the fossil record in East Africa for 1975. Yrbk. Phys.
Anthr. 19–35 (1976).
6. Toth, N. The Oldowan reassessed: a close look at early stone artifacts.
J. Archaeol. Sci. 12, 101–120 (1985).
7. Delagnes, A. & Roche, H. Late Pliocene hominid knapping skills: the case
of Lokalalei 2C, West Turkana, Kenya. J. Hum. Evol. 48, 435–472 (2005).
Figure 3 | Examples of passive hammers from capuchin SoS percussion.
a, b, Passive hammers with detail of percussive damage (inset). c, Passive
hammer in situ at Serra da Capivara National Park, after its observed use
for SoS percussive behaviour. Note the small flake fragments at the base
of the passive element, resulting from active hammer flaking. a–c, Main
scale bars are 5 cm, the scale bars in the insets (a, b) are 1 cm.
ab
c
© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

4 | NATURE | VOL 000 | 00 MONTH 2016
LETTER
RESEARCH
8. Semaw, S. The world’s oldest stone artefacts from Gona, Ethiopia: their
implications for understanding stone technology and patterns of human
evolution between 2·6–1·5 million years ago. J. Archaeol. Sci. 27, 1197–1214
(2000).
9. Stout, D., Semaw, S., Rogers, M. J. & Cauche, D. Technological variation in the
earliest Oldowan from Gona, Afar, Ethiopia. J. Hum. Evol. 58, 474–491 (2010).
10. de la Torre, I. Omo revisited: evaluating the technological skills of Pliocene
hominids. Curr. Anthropol. 45, 439–465 (2004).
11. Lewis, J. E. & Harmand, S. An earlier origin for stone tool making: implications
for cognitive evolution and the transition to Homo. Phil. Trans. R. Soc. B 371,
20150233 (2016).
12. Boëda, E. et al. A new late Pleistocene archaeological sequence in South
America: the Vale da Pedra Furada (Piauí, Brazil). Antiquity 88, 927–941
(2014).
13. Matsuzawa, T., Humle, T. & Sugiyama, Y. The Chimpanzees of Bossou and Nimba.
(Springer Science & Business Media, 2011).
14. Mercader, J., Panger, M. & Boesch, C. Excavation of a chimpanzee stone tool
site in the African rainforest. Science 296, 1452–1455 (2002).
15. McGrew, W. C. Chimpanzee Material Culture: Implications for Human Evolution.
(Cambridge Univ. Press, 1992).
16. Mercader, J. et al. 4,300-year-old chimpanzee sites and the origins of
percussive stone technology. Proc. Natl Acad. Sci. USA 104, 3043–3048
(2007).
17. Pelegrin, J. in Stone Knapping: The Necessary Conditions for a Uniquely Hominid
Behaviour. (eds Roux, V. & Bril, B.) 23–33 (McDonald Institute monograph
series, 2005).
18. Toth, N., Schick, K. & Semaw, S. in The Oldowan: Case Studies into the Earliest
Stone Age (eds Toth, N. & Schick, K.) 155–222 (Stone Age Institute Press,
2006).
19. Falótico, T. & Ottoni, E. B. The manifold use of pounding stone tools by wild
capuchin monkeys of Serra da Capivara National Park, Brazil. Behaviour 153,
421–442 (2016).
20. Mannu, M. & Ottoni, E. B. The enhanced tool-kit of two groups of wild bearded
capuchin monkeys in the Caatinga: tool making, associative use, and
secondary tools. Am. J. Primatol. 71, 242–251 (2009).
21. Falótico, T. & Ottoni, E. B. Stone throwing as a sexual display in wild female
bearded capuchin monkeys, Sapajus libidinosus. PLoS One 8, e79535 (2013).
22. Leca, J.-B., Gunst, N. & Human, M. Complexity in object manipulation by
Japanese macaques (Macaca fuscata): a cross-sectional analysis of manual
coordination in stone handling patterns. J. Comp. Psychol. 125, 61–71 (2011).
23. Moura, A. C. Stone banging by wild capuchin monkeys: an unusual auditory
display. Folia Primatol. (Basel) 78, 36–45 (2007).
24. Carlisle, E. M. Silicon as an essential trace element in animal nutrition. Silicon
Biochem. 703, 123–139 (2008).
Supplementary Information is available in the online version of the paper.
Acknowledgements The study was funded by a European Research
Council Starting Investigator Grant (#283959) to M.H. and São Paulo
Research Foundation (FAPESP) awards to T.F. (#2013/05219-0) and E.B.O.
(#2014/04818-0). Support for fieldwork and analysis was provided by
N. Guidon and G. Daltrini Felice of FUMDHAM and University College London
(ERC Starting Grant #283366). We thank R. Fonseca de Oliveira for excavation
coordination, M. Gumert, R. Mora and A. Arroyo for comments, and
A. Theodoropoulou for artefact illustrations. Fieldwork at SCNP was
approved by Brazilian environmental protection agencies (IBAMA/ICMBio
37615-2).
Author Contributions M.H. and T.F. observed and recorded the capuchin
behaviour, collected lithic material and directed excavations at Serra da
Capivara National Park. T.P. conducted the technological analysis. T.P., L.V.L.,
I.D.L.T. and M.H. discussed the implications of the results. T.P. wrote the paper
and supplementary online content with contributions from L.V.L., T.F., E.B.O.,
I.D.L.T. and M.H. T.P generated all figures, 3D models and video content, using
data recorded by M.H. and T.P.
Author Information Reprints and permissions information is available at
www.nature.com/reprints. The authors declare no competing financial
interests. Readers are welcome to comment on the online version of the paper.
Correspondence and requests for materials should be addressed to
T.P. (tomos.proffitt@arch.ox.ac.uk) or M.H. (michael.haslam@arch.ox.ac.uk).
Reviewer Information Nature thanks S. Carvalho and H. Roche for their
contribution to the peer review of this work.
25. Isaac, G. L. Koobi Fora Research Project Vol. 5: Plio-Pleistocene Archaeology.
(Clarendon, 1997).
26. Haslam, M. et al. Pre-Columbian monkey tools. Curr. Biol. 26, R521–R522
(2016).
27. Haslam, M. Towards a prehistory of primates. Antiquity 86, 299–315
(2012).
28. Kivell, T. L. Evidence in hand: recent discoveries and the early evolution
of human manual manipulation. Phil. Trans. R. Soc. B 370, 20150105
(2015).
29. de la Torre, I. in Stone Tools and the Evolution of Human Cognition. (eds Nowell,
A. & Davidson, I.) 45–65 (Univ. Press of Colorado, 2010).
30. McPherron, S. P. et al. Evidence for stone-tool-assisted consumption of animal
tissues before 3.39 million years ago at Dikika, Ethiopia. Nature 466, 857–860
(2010).
© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

LETTER RESEARCH
31. Pessiss, A.-M., Martin, G. & Guidon, N. Os Biomad e as Sociedades Huanas na
Pre-Historia da Regiao do Parque nacional Serra da Capivara, Brasil. Volume II
A–B. (Fundação Museu Do Homem Americano—Fumdham, Ipsis Gráca E
Editora, 2014).
32. Inizan, M.-L., Reduron-Ballinger, M. & Roche, H. Technology and Terminology
of Knapped Stone: Followed by a Multilingual Vocabulary Arabic, English, French,
German, Greek, Italian, Portuguese, Spanish. 5, (Cercle de Recherches et
d’Etudes Préhistoriques, 1999).
33. De la Torre, I. & Mora, R. Technological Strategies in the Lower Pleistocene at
Olduvai Beds I & II. (Univ. Liège press, ERAUL, 2005).
OIT 2. We excavated Lasca OIT 1 (Extended Data Fig. 1a), located 120 m southwest
of Lasca OIT 2, beneath the sheer face of an approximately 7 m high conglomerate
outcrop that showed percussion marks indicative of previous SoS activity. A total
excavated area of 3 m
2
to a maximum depth of 0.4 m yielded 23 artefacts (20.7%)
at this site. We did not find human material, such as hearths, ceramic pieces, metal
objects, or ground stone at either site. Such items are ubiquitous in anthropogenic
sites elsewhere in SCNP
31
. This absence, along with direct observation of capuchins
creating the flaked surface assemblage, and the identical nature of the damage and
size of the recovered stones to those observed in use by capuchins, rules out human
production of the archaeological material.
No statistical methods were used to predetermine sample size. The experiments
were not randomized. The investigators were not blinded to allocation during
experiments and outcome assessment.
We identified the raw material of each artefact and performed technological
classification and analysis following commonly used technological attributes
7,9,32,33
.
For full details and definitions of the technological categories used in this analysis,
see the Supplementary Information. All data are available upon request.
METHODS
The SoS percussion assemblage included 111 artefacts collected from surface and
archaeological capuchin activity locations in Serra da Capivara National Park
(SCNP), PIauí, Brazil. The surface collection (Lasca OIT surface; n = 60, 54.1%)
was produced by capuchins observed performing SoS percussion in September
2014, at a site later designated Lasca Oitente 2 (L asca OIT 2). The capuchins belong
to the Jurubeba group, which was first studied in March 2004 (ref. 20). SoS activity
primarily took place on a low (approximately 1 m high), narrow conglomerate
ridge associated with a much larger conglomerat ic outcrop (Fig. 1; Supplementary
Video 1). During this time a portion of the used assemblage dropp ed to the ground
immediately below the activity area, and was collected once the activity ceased.
Additional material was collected during surface surveys within the immediate
vicinity of Lasca OIT 2, at locations where isolated conglomerate blocks were used
by the same capuchin group for SoS percussion. This material was also analysed
as Lasca OIT surface.
The archaeological material comes from two excavations conducted in June
2015 (Extended Data Fig. 1), within the Jurubeba group range: Lasca OIT 1
(8° 52.460′ S, 42° 37.977′ W) and Lasca OIT 2 (8° 52.394′ S, 42° 37.971′ W). We
excavated both sites by hand in 5-cm levels, and sieved all sediment through a
5 mm mesh. Sediments at both sites consisted of light-brown, silty sand, with
gravel to cobble-sized inclusions, resulting from the in situ weathering of local
conglomerates. We distinguished capuchin tools from natural stones on the basis of
percussion marks and flaking features as described in the main text and below. The
Lasca OIT 2 excavation (Extended Data Fig. 1b) can be considered an extension of
the surface material collected in 2014 from the same site. An area of 3 m
2
excavated
to a maximum depth of 0.5 m yielded 28 SoS p erc ussion artefacts (25.2%) at Lasca
© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

LETTER
RESEARCH
Extended Data Figure 1 | Archaeological excavation of wild capuchin
SoS percussion sites, Serra da Capivara National Park. a, Lasca OIT1
excavation, each square is 1 × 1 m. b, The approach to Lasca OIT2,
which is located to the right of the conglomerate cliff face. c, Lasca
OIT2 excavation, note the low conglomerate ridge to the left, on which
capuchins were observed whilst performing SoS activities. Scale bar,
30 cm (see also Fig. 1).
© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

LETTER RESEARCH
Extended Data Figure 2 | Examples of active hammers. a, Crushing impacts on multiple surfaces of an active hammer. b, Examples of impact points
and associated circular hertzian fractures on the surface of an active hammer. Scale bars are 5 cm, except for inset scale bars, which are 2 mm.
© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

LETTER
RESEARCH
Extended Data Figure 3 | Examples of SoS flaked hammer-stones. a, c, Flake detachment following a transverse active hammer fracture.
b, Unintentional radial reduction of flaked hammer-stone. d–f, Examples of complete active hammers with scars of accidental flakes. Scale bars
are 5 cm.
© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

LETTER RESEARCH
Extended Data Figure 4 | Refits of flaked hammer-stones showing the
repeated detachment of unidirectional flakes. a, Refit Set 1 (artefact
numbers JC13 and JF7). b, Refit Set 2 (artefact numbers 225102a and
225102b). c, Refit Set 3 (artefact numbers 224881a and 224881b). d, Refit
Set 4 (artefact numbers JF3 and JC5). A, A2, B and C are designated planes
on each refit, corresponding to descriptions found in Supplementary
Information. Scale bars are 5 cm.
© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

LETTER
RESEARCH
Extended Data Figure 5 | Refits of flaked hammer-stones showing the
repeated detachment of unidirectional flakes and continued use of
broken active hammers. a, Refit Set 5 (artefact numbers JC11, JC12, JF23
and JF1). b, Refit Set 6 (artefact numbers JC6, JF2, JF14, JF4 and JF8)
(See also Supplementary Video 2). c, Refit Set 7 (artefact numbers
JC4 and JC10). A, A2, B, B2, C and C2 are designated planes on each refit,
corresponding to descriptions found in Supplementary Information. Scale
bars are 5 cm.
© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

LETTER RESEARCH
Extended Data Figure 6 | Examples of complete flakes. a–f, Examples of complete flakes detached during capuchin SoS percussion. Scale bars are
in cm. Scale bars are 5 cm.
© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

LETTER
RESEARCH
Extended Data Table 1 | Absolute and relative frequencies and total weights (g) of technological categories identified in each Capuchin SoS
assemblage, Serra da Capivara National Park
© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

LETTER RESEARCH
Extended Data Table 2 | Dimensional data for all artefacts from Capuchin SoS assemblages and a comparison with
Pliocene–Pleistocene hominin artefacts
a, Dimension data for all technological categories identied in this study. b, Metric comparison of SCNP capuchin SoS percussion akes and aked hammer-stones with hominin
Pliocene–Pleistocene ake and core dimensions. Data and table adapted from Harmand et al. (2015).
© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.