The EconomistJune 29th 2019 Science & technology 772 However,thestrangeteethofancientcroc-
odiles, they reasoned, might give opcr
somethingtoworkwith.
Intotal,theythrew 146 teethfrom 16 ex-
tinctcrocodiliansatopcr. Forcomparison,
theyalsoaddedteethfroma moderncai-
manintothemix.Theanalysisrevealed
thattwooftheextinctspecieswere,likethe
caiman,carnivorous.Buteventhesewere
notablydifferentfrommodernanimalsin
thatonehadserratedsteak-knife-liketeeth
and theother had triangular teeth that
madecontactwithoneanotherwhenthe
animalcloseditsmouth(somethingnot
seeninmoderncrocodilians).Thesystem
identifiedtwoofthespeciesas“duropha-
gus”,meaningthattheirteethlookedasif
theywouldbegoodatcrushingtheshells
ofclams,crabsandotherarmouredinver-
tebrates.Onespecieswasidentifiedasom-
nivorous.Andeight,includingSimosuchus,
wereidentifiedbyopcrasobligateherbi-
vores.(Theotherthreewerehardtoclassi-
fy,butmayhavebeeninsectivores.)
What particularly surprised Mr Mel-
stromandDrIrmis,though,wastheway
herbivorymappedontothecrocodilefam-
ilytree.Ratherthanevolvingonceatsome
pointlongagoandthenappearinginalllat-
erspeciesonthatbranch,it cameintoexis-
tenceatleastthreetimesduringthehistory
ofthesereptiles.Herbivorouscrocodilesof
theJurassicandCretaceous,then,wereca-
pableofcompetingsuccessfullywiththeir
dinosaurcounterpartsina waythata mod-
ern herbivorous crocodile presumably
couldnotwiththeplethoraofherbivorous
mammalsthatnowexists. 7
O
ne of themost famous edits in cine-
matic history comes early in “2001: A
Space Odyssey”. A primitive hominid hurls
a bone club into the air, and a match cut to a
spacecraft instantaneously tells the mil-
lennia-long story of human ingenuity.
Tools maketh man. But there was never a
human monopoly on tool use, as a new pa-
per in Nature Ecology & Evolutionshows. A
team led by Tiago Falótico of the University
of São Paulo, in Brazil, and Tomos Proffitt of
University College, London, has demon-
strated that a species of monkey called the
wild bearded capuchin has been employ-
ing stone tools for perhaps 3,000 years, and
that their use of the technology has
changed over the course of time.
Capuchins, chimpanzees and sea ot-ters,amongothers,are known to use rocks
to crack open, respectively, nuts and shell-
fish. And an earlier dig by Dr Falótico found
evidence that, in capuchins, this habit goes
back at least 600 years. Though some may
question whether bashing a nut with a rock
truly qualifies as “tool use”, capuchins (as
the picture shows) use both hammerstones
and anvils—which demonstrates quite a
high level of sophistication.
They also demonstrate sophistication
in the wielding of their tools, because not
damaging the soft kernel of a nut while
breaking the shell takes skill. Cracking
open a cashew, the favourite for this treat-
ment, requires the tool-wielder to employ
a single, practised motion. First, the ani-
mal brings the hammerstone down two-
handed for a glancing blow on the nut’s far
side. It then rolls the stone towards itself,
over the nut. Youngsters take around eight
years of mimicking their parents to get the
knack of all this. And although the stones
used are not actually modified for the task,
monkeys are assiduous in searching for
and selecting those of the perfect shape.
(They do, however, lack the insight to keep
such stones for future use.)
Dr Falótico and Dr Proffitt returned to
the site of the previous excavation—a part
of Serra da Capivara National Park in the
Brazilian Amazon. They dug into an area of
67 square metres, to which the monkeys
bring stones from a nearby stream bed. The
site’s capuchins use quartzite cobbles as
hammerstones, and tree limbs and loose
stones as anvils.
By excavating 1,699 stones, pebbles and
flakes, and working out the age of 122 ham-
merstones from the radiocarbon dates of
charcoal buried alongside them, the team
split the site’s history into four phases. Ca-
puchins first swung a rock in the area
somewhere between 3,000 and 2,400 years
ago—the beginning of a period the re-
searchers call Phase IV. This is the oldestknown instance of non-ape tool use. Phase
IV hammerstones are light and have many
impact marks. This suggests they were
used mainly on seeds (possibly from cassa-
va) smaller than the cashews which today’s
monkeys pound, meaning hammerstone
and anvil often came into contact with one
another.
Phase III, between 640 and 565 years
ago, featured transitional behaviours that
led to Phase II, from about 257 years ago,
when hammerstones were heavier and are
associated with many large anvils, suggest-
ing a food source bigger and harder than
cashews (the hard-shelled jatoba fruit is a
possibility). More recently, in Phase I (from
27 years ago), cashew residue on stones
suggests the monkeys were moving to-
wards their present-day alimentary focus.
What Dr Falótico and Dr Proffitt do not yet
know is whether the variation they saw is a
result of different groups of capuchins,
with different habits, occupying the site at
different times—or, alternatively, whether
a single lineage of the animals has changed
its nutritional culture over the years.
Until Dr Falótico’s original dig, chimps
were the only species other than human
beings for which an archaeological record
of tool use had been found. (In 2007 re-
searchers discovered chimpanzee-modi-
fied stones that were 4,300 years old.)
There is no reason, though, not to expect
the finding of further, and perhaps older,
sites in future. Moreover, studying how ca-
puchins and chimps have used tools may
give an inkling of how the process hap-
pened in people. One thing Dr Falótico and
Dr Proffitt have noticed is that some of the
sharp flakes that fly off when hammer
meets anvil look identical to Stone Age
blades made by human beings. Capuchins
have not yet—so far as is known—thought
to use such flakes as knives. But perhaps
their own “2001” moment awaits them in
the future.^7Capuchin monkeys have been using
stone tools for around 3,000 yearsAnimal archaeologyBang the rocks
together, guys
Nutcracker suite