TheCognitivenicheCoevolutionofintelligencesocialityandlanguage.pdf

The cognitive niche: Coevolution of intelligence,
sociality, and language
Steven Pinker1

Department of Psychology, Harvard University, Cambridge, MA 02138

Although Darwin insisted that human intelligence could be fully
explained by the theory of evolution, the codiscoverer of natural
selection, Alfred Russel Wallace, claimed that abstract intelligence
was of no use to ancestral humans and could only be explained by
intelligent design. Wallace’s apparent paradox can be dissolved with
two hypotheses about human cognition. One is that intelligence is an
adaptation to a knowledge-using, socially interdependent lifestyle,
the “cognitive niche.” This embraces the ability to overcome the evo-
lutionary fixed defenses of plants and animals by applications of rea-
soning, including weapons, traps, coordinated driving of game, and
detoxification of plants. Such reasoning exploits intuitive theories
about different aspects of the world, such as objects, forces, paths,
places, states, substances, and other people’s beliefs and desires. The
theory explains many zoologically unusual traits in Homo sapiens,
including our complex toolkit, wide range of habitats and diets,
extended childhoods and long lives, hypersociality, complex mating,
division into cultures, and language (which multiplies the benefit of
knowledge because know-how is useful not only for its practical
benefits but as a trade good with others, enhancing the evolution
of cooperation). The second hypothesis is that humans possess an
ability of metaphorical abstraction, which allows them to coopt fac-
ulties that originally evolved for physical problem-solving and social
coordination, apply them to abstract subject matter, and combine
them productively. These abilities can help explain the emergence
of abstract cognition without supernatural or exotic evolutionary
forces and are in principle testable by analyses of statistical signs of
selection in the human genome.

cognition | human evolution | metaphor

The bicentennial of Darwin’s birth and sesquicentennial of thepublication of the Origin of Species have focused the world’s
attention on the breathtaking scope of the theory of natural
selection, not least its application to the human mind. “Psychology
will be based on a new foundation,” Darwin famously wrote at the
end of the Origin, “that of the necessary acquirement of each
mental power and capacity by gradation. Light will be thrown on
the origin of man and his history.”
Far less attention has been given to the codiscoverer of natural

selection, Alfred Russel Wallace, despite his prodigious scientific
genius, and it is unlikely that the bicentennial of his birth in 1823 will
generate the same hoopla. One reason was that Wallace turned out
to be less prescient about the power of natural selection as an
explanation of adaptive complexity in the living world. In particular,
Wallace notoriously claimed that the theory of evolution by natural
selection was inadequate to explain human intelligence:

Our law, our government, and our science continually require us to
reason through a variety of complicated phenomena to the expected
result. Even our games, such as chess, compel us to exercise all these
faculties in a remarkable degree. . . . A brain slightly larger than that
of the gorilla would . . . fully have sufficed for the limited mental
development of the savage; and we must therefore admit that the
large brain he actually possesses could never have been solely
developed by any of those laws of evolution, whose essence is, that
they lead to a degree of organization exactly proportionate to the
wants of each species, never beyond those wants. . ..

Natural selection could only have endowed savage man with a brain
a few degrees superior to that of an ape, whereas he actually pos-

sesses one very little inferior to that of a philosopher. (1, pp.
340, 343.)

The upshot, claimed Wallace, was that “a superior intelligence
has guided the development of man in a definite direction, and
for a special purpose (1, p 359). ”
Few scientists today accept Wallace’s creationism, teleology, or

spiritualism. Nonetheless it is appropriate to engage the profound
puzzle he raised; namely, why do humans have the ability to pursue
abstract intellectual feats such as science, mathematics, philoso-
phy, and law, given that opportunities to exercise these talents did
not exist in the foraging lifestyle in which humans evolved and
would not have parlayed themselves into advantages in survival
and reproduction even if they did?
I suggest that the puzzle can be resolved with two hypotheses.

The first is that humans evolved to fill the “cognitive niche,” a
mode of survival characterized by manipulating the environment
through causal reasoning and social cooperation. The second is
that the psychological faculties that evolved to prosper in the
cognitive niche can be coopted to abstract domains by processes of
metaphorical abstraction and productive combination, both viv-
idly manifested in human language.

The Cognitive Niche
The term cognitive niche was proposed by Toobyand DeVore (2) to
explain the constellation of zoologically unusual features of modern
Homo sapiens without resorting to exotic evolutionary mechanisms.
Their account begins with the biological commonplace that

organisms evolve at one another’s expense. With the exception of
fruit, virtually every food source of one animal isa body part ofsome
other organism, which would just as soon keep that body part for
itself. As a result, organisms evolve defenses against being eaten.
Animals evolve speed, stealth, armor, and defensive maneuvers.
Plants cannot defend themselves with their behavior, so they resort
to chemical warfare, and have evolved a pharmacopeia of poisons,
irritants, and bitter-tasting substances to deter herbivores with
designs on their flesh. In response, eaters evolve measures to pen-
etrate thesedefenses, such asoffensive weapons, evengreater speed
or stealth, and organs such as the liver that detoxify plant poisons.
This in turn selects for better defenses, selecting for better offenses,
and so on, in a coevolutionary arms race, escalating over many
generations of natural selection.
Tooby and DeVore (2) suggest that humans exploit a cognitive

niche in the world’s ecosystems. In biology, a “niche” is sometimes
defined as “the role an organism occupies in an ecosystem.” The
cognitive niche is a loose extension of this concept, based on the
idea that in any ecosystem, the possibility exists for an organism to
overtake other organisms’ fixed defenses by cause-and-effect
reasoning and cooperative action—to deploy information and

This paper results from the Arthur M. Sackler Colloquium of the National Academy of
Sciences, “In the Light of Evolution IV: The Human Condition,” held December 10–12,
2009, at the Arnold and Mabel Beckman Center of the National Academies of Sciences
and Engineering in Irvine, CA. The complete program and audio files of most presentations
are available on the NAS Web site at www.nasonline.org/SACKLER_Human_Condition.

Author contributions: S.P. designed research; performed research; and wrote the paper.

The author declares no conflict of interest.

This article is a PNAS Direct Submission.
1E-mail: [email protected].

www.pnas.org/cgi/doi/10.1073/pnas.0914630107 PNAS | May 11, 2010 | vol. 107 | suppl. 2 | 8993–8999

http://www.nasonline.org/SACKLER_Human_Condition

inference, rather than particular features of physics and chemistry,
to extract resources from other organisms in opposition to their
adaptations to protect those resources. These inferences are
played out internally in mental models of the world, governed by
intuitive conceptions of physics, biology, and psychology, including
the psychology of animals. It allows humans to invent tools, traps,
and weapons, to extract poisons and drugs from other animals and
plants, and to engage in coordinated action, for example, fanning
out over a landscape to drive and concentrate game, in effect
functioning like a huge superorganism. These cognitive stratagems
are devised on the fly in endless combination suitable to the local
ecology. They arise by mental design and are deployed, tested, and
fine-tuned by feedback in the lifetimes of individuals, rather than
arising by random mutation and being tuned over generations by
the slow feedback of differential survival and reproduction.
Because humans develop offenses in real time that other organ-
isms can defend themselves against only in evolutionary time,
humans have a tremendous advantage in evolutionary arms races.
Even before the current anthropogenic mass extinction, pre-
historic humans are believed to have caused significant extinctions
of large fauna whenever they first entered an ecosystem.
The theory of the cognitive niche helps explain many zoologi-

cally unusual features of H. sapiens: traits that are universal across
human cultures (3) but are either unique or hyperdeveloped
(especially in combination) with respect to the rest of the animal
kingdom. Three in particular make our species stand out.

Technological Know-How. Humansuseand dependuponmanykinds
of tools, which involve multiple parts and complicated methods of
fabrication. The tools are deployed in extended sequences of
behavior and are acquired both by individual discovery and learning
from others. They are deployed to capture and kill animals, to
process foods (including cooking, fermenting, soaking, peeling, and
crushing them to remove toxins and increase the availability of
nutrients), and to generate and administer medicinal drugs (4, 5).
This reasoning is supported by “intuitive theories”—folk under-
standings of physics (in particular, objects, substances, and the
forces that impinge on them), geometry (places, paths, and direc-
tions), biology (essences that give organisms their form and propel
their growth, motion, and physiological processes), and psychology
(internal, immaterial beliefs and desires) (6–10).

Cooperation Among Nonkin. Humans cooperate with other humans:
they trade goods, favors, know-how, and loyalty, and act collectively
in child-rearing, gathering, hunting, and defense. This cooperation
extends to other humans who are not related to them, in shifting
partnerships, coalitions, and trading relationships, and thus must be
explained not by kin selection but by mutualism or reciprocity (11).
The evolution of cooperation by reciprocal altruism requires a

number of cognitive adaptations, which in fact appear to be well-
developed in humans (11). They include the recognition of indi-
viduals (12); episodic memory for their actions (13); an ability to
classify those actions in terms of whether they violate a reciprocity
contract (14, 15); a suite of moral emotions such as sympathy,
gratitude, anger, guilt, and trust, which impel an individual to
initiate cooperation, reward reciprocators, and punish cheaters
(11, 16); and the drives to ascertain the competence, integrity, and
generosity of others (through gossip and other forms of due dili-
gence)and to burnish one’sown reputation for these traits (17, 18).
Because humans cooperate by at least three different kinds of

relationship, governed by incompatible rules for the distribution of
resources—reciprocal altruism, mutualistic sharing, deferring to
dominant individuals—dyads can dynamically switch among kinds
of relationship according to their history, kinship, social support,
the resource at stake, and the context (19). The demands of this
negotiation account for many of the complex aspects of human
social life such as politeness, hypocrisy, ritual, and taboo (20, 21).

Grammatical Language. Although many animals communicate,
humans appear to be unique in using an open-ended combinatorial
system, grammatical language. In grammatical language, signals
(words) are arbitrarily paired with concepts, and can be rearranged
in novel hierarchical configurations (phrases embedded within
phrases) in such a way that the meaning of the sequence can be
computed from the meanings of the individual symbols and the way
that they are arranged (22–24). The semantic meanings of the
symbols (nouns, verbs, prepositions, tense markers, and so on) are
related to the basic cognitive categories that define intuitive theo-
ries: objects, substances, motion, causation, agency, space, time (9,
25). The syntactic arrangements serve to express relationships
among these concepts such as who did what to whom, what is where,
and what is true of what (9). Although every language must be
learned, humans have an ability to coin, pool, and learn new words
and rules and thus are not dependent on some other species as
teachers (as is the case with apes), or even on a longstanding lin-
guistic community, to develop and use language (26).
Grammatical language has clear advantages in the transmission

of information. Because it allows messages to be composed out of
elements, rather than drawn from a finite repertoire, it confers the
ability to express an unlimited number of novel messages (27, 28).
Journalists say that when a dog bites a man, that is not news, but
when a man bites a dog, that is news: the power of grammar is that it
allows us to convey news, by arranging familiar words in novel
combinations. Like other digital combinatorial systems in biology
(RNA, DNA, proteins), language can generate vast numbers of
structured combinations. The number of possible sentences (each
corresponding to a distinct message) is proportional to the number
of words that may appear in a position in a sentence raised to the
powerofthelength ofthesentence.With an approximate geometric
meanoftenchoicesavailableateverypositioninasentence,onecan
estimate that a typical English speaker can easily produce or com-
prehend at least 1020 distinct sentences (29). This in turn makes it
possible for language users to share an unlimited number of mes-
sages concerning specific events (who did what to whom, when,
where, and why), generalized expertise (to accomplish this, do
that), and flexible social contracts (if you do this, I’ll do that).
Anyone who is skeptical that sophisticated reasoning, collabo-

ration, and communication can bring survival advantages in a pre-
historic lifestyle need only read ethnographic accounts of hunting or
gatheringincontemporaryforaging peoples.One ofmanyexamples
of hunter-gatherer ingenuity can be found in this description from
the anthropologist Napoleon Chagnon of how the Yanomamö
hunt armadillo:

Armadillos live several feet underground in burrows that can run
for many yards and have several entries. When the Yanomamö find
an active burrow, as determined by the presence around the entry of a
cloud of insects found nowhere else, they set about smoking out the
armadillo. The best fuel for this purpose is a crusty material from old
termite nests, which burns slowly and produces an intense heat and
much heavy smoke. A pile of this material is ignited at the entry of the
burrow, and the smoke is fanned inside. The other entries are soon
detected by the smoke rising from them, and they are sealed with dirt.
The men then spread out on hands and knees, holding their ears to
the ground to listen for armadillo movements in the burrow. When
they hear something, they dig there until they hit the burrow and, with
luck, the animal. They might have to try several times, and it is hard
work—they have to dig down two feet or more. On one occasion,
after the hunters had dug several holes, all unsuccessful. . .one of
them ripped down a large vine, tied a knot in the end of it, and put the
knotted end into the entrance. Twirling the vine between his hands,
he slowly pushed it into the hole as far as it would go. As his com-
panions put their ears to the ground, he twirled the vine, causing the
knot to make a noise, and the spot was marked. He broke off the vine
at the burrow entrance, pulled out the piece in the hole, and laid it on
the ground along the axis of the burrow. The others dug down at the
place where they had heard the knot and found the armadillo on their
first attempt, asphyxiated from the smoke (30, pp 78–79.).

8994 | www.pnas.org/cgi/doi/10.1073/pnas.0914630107 Pinker

This jackpot was a reward for extraordinary feats of folk
reasoning in taxonomy, physiology, physics, and geometry, some
passed down from earlier generations, some improvised on the
spot. And it depended on cooperative behavior among many
individuals, coordinated by language.

Other Extreme Human Traits. Other zoologically unusual features of
H.sapiensmay beexplainedbythetheoryofthecognitiveniche.The
vast range of habitats and foods exploited by our species may in part
have been facilitated by natural selection of the genes in local
populations to ambient conditions such as solar radiation, diet, and
disease (31–34). But the these local adaptations pale in comparison
with those made possible by human technology. The Inuit’s colo-
nization of high latitudes may have been facilitated by adaptive
changes inbody shape and skin pigmentation, butitdependedmuch
more on parkas, kayaks, mukluks, igloos, and harpoons. This
underscores that the cognitive niche differs from many examples of
niches discussed in biology in being defined not as a particular
envelope of environmental variables (temperature, altitude, habitat
type, and so on), nor asa particular combination ofother organisms,
but rather the opportunity that any environment provides for
exploitation via internal modeling of its causal contingencies.
Our extended childhoods may serve as an apprenticeship in a

species that lives by its wits, and our long lives may reflect a tilt in
the tradeoff between reproduction and somatic maintenance
toward the latter so as to maximize the returns on the investment
during childhood. The dependence of children’s readiness for
adulthood on their mastery of local culture and know-how may
also shift the balance in male parental investment decisions
between caring for existing offspring and seeking new mating
opportunities. This in turn may have led to biparental care, long-
term pair bonding, complex sexuality (such as female sexuality
being unlinked from fertility, and sexual relationships subject to
variation and negotiation), and multigeneration parental invest-
ment (35). Support for these hypotheses comes from the data of
Kaplan (36), who has shown that among hunter-gatherers, pro-
longed childhood cannot pay off without long life spans. The men
do not produce as many calories as they consume until age 18;
their output then peaks at 32, plateaus through 45, then gently
declines until 65. This shows that hunting is a knowledge-
dependent skill, invested in during a long childhood and paid out
over a long life.
Finally, the division of humankind into cultures differing in

language, customs, mores, diets, and so on, is a consequence of
humans’ dependence on learned information (words, recipes, tool
styles, survival techniques, cooperative agreements, and customs)
and their peripatetic natures. As splinter groups lose touch with
their progenitors over time, the know-how and customs that the
two groups accumulate will diverge from one another (37).

Hominid Evolution and the Cognitive Niche. Given that the oppor-
tunity to exploit environments by technology and cooperation are
independent of particular ecosystems, why was it Pliocene homi-
nids that entered (or, more accurately, constructed) the cognitive
niche and evolved sophisticated cognition, language, and sociality,
rather than a population from some other taxon or epoch? This
kind ofhistoricalquestionisdifficult,perhapsimpossible,toanswer
precisely because the unusualness of H. sapiens precludes statistical
tests of correlations between the relevant traits and environments
across species. But if we consider the cognitive niche as a suite of
mutually reinforcing selection pressures, each of which exists
individually in weaker form for other species, we can test whether
variation in intelligence within a smaller range, together with a
consideration of the traits that were likely possessed by extinct
human ancestors, supports particular conjectures.
Obviously any orthogenetic theory (such as Wallace’s) stip-

ulating that the emergence our species was the goal of the evolu-
tionary process is inconsistent with the known mechanisms of

evolution. It is also apparent that intelligence, which depends on a
large brain, is not a free good in evolution (38). Its costs include the
metabolic demands of expensive neural tissue, compromises in the
anatomy of the female pelvis necessary for bearing a large-headed
offspring, and the risks of harm from birth, falls, and the mutation
and parasite load carried by such a complex organ. The proper
framing of the question must ask which circumstances made the
benefits of intelligence outweigh the costs. The hypothesis is that
the hominid ancestors, more so than any other species, had a
collection of traits that had tilted the payoffs toward further
investment in intelligence.
One enabling factor may have been the possession of prehensile

hands (an adaptation to arboreality) in combination with biped-
ality (presumably an adaptation to locomotion). We know from
the fossil record that both preceded the expansion of the brain and
the development of tool use (39). Perhaps the availability of pre-
cision manipulators meant that any enhanced ability to imagine
how one might alter the environment could be parlayed into the
manufacture and carrying of tools.
A second contributor to the evolution of intelligence among

hominid ancestors may have been an opportunistic diet that inclu-
ded meat and other hard-to-obtain sources of protein (5). Meat is
not only a concentrated source of nutrients for a hungry brain but
mayhaveselectedinturnforgreaterintelligence,becauseitrequires
more cleverness to outwit an animal than to outwit fruit or leaves.
A third may have been group living, again with the possibility

of positive feedback: groups allow acquired skills to be shared
but also select for the social intelligence needed to prosper from
cooperation without being exploited.
Indirect support for the hypothesis that sociality and carnivory

contributed to the evolution of human intelligence comes from
comparative studies showing that greater intelligence across
animal species is correlated with brain size, carnivory, group size,
and extended childhoods and lifespans (40, 41). I am unaware of
any review that has looked for a correlation between possession
of prehensile appendages and intelligence, although it is tanta-
lizing to learn that octopuses are highly intelligent (42).

Coevolution of Cognition, Language, and Sociality. Many biologists
arguethatanicheissomethingthatisconstructed,ratherthansimply
entered, by an organism (43, 44). An organism’s behavior alters its
physical surroundings, which affects the selection pressures, in turn
selecting for additional adaptations to exploit that altered envi-
ronment, and so on. A classic example is the way beavers generated
an aquatic niche and evolved additional adaptations to thrive in it.
The particulars of a cognitive niche are similarly constructed, in the
sense that initial increments in cooperation, communication, or
know-how altered the social environment, and hence the selection
pressures, for ancestral hominids. It is surely no coincidence that the
psychological abilities underlying technological know-how, open-
ended communication, and cooperation among nonkin are all
hyperdeveloped in the same species; each enhances the value of the
other two. (A similar feedback loop may connect intelligence with
the life-history and behavioral-ecology variables mentioned in the
preceding section.)
An obvious interdependency connects language and know-how.

The end product of learning survival skills is information stored
in one’s brain. Language is a means of transmitting that infor-
mation to another brain. The ability to share information via lan-
guage leverages the value of acquiring new knowledge and skills.
One does not have to recapitulate the trial-and-error, lucky
accidents, or strokes of genius of other individuals but can build
on their discoveries, avoiding the proverbial waste of reinventing
the wheel.
Language not only lowers the cost of acquiring a complex skill

but multiplies the benefit. The knowledge not only can be
exploited to manipulate the environment, but it can be shared with
kin and other cooperators. Indeed, among commodities, infor-

Pinker PNAS | May 11, 2010 | vol. 107 | suppl. 2 | 8995

mation is unusually conducive to being shared because it is what
economists call a “nonrival good”: it can be duplicated without
loss. If I give you a fish (a rival good), I no longer have the fish; as
the saying might have gone, you cannot eat your fish and have it.
But if I teach you to fish, it does not mean that I am now amnesic
for the skill of fishing; that valuable commodity now exists in twice
as many copies. Language can multiply this proliferation: for the
minor cost of a few seconds of breath, a speaker can confer on a
listener the invaluable benefit of a new bit of know-how. Crucially,
a commodity that confers a high benefit on others at a low cost to
the self is a key ingredient in the evolution of cooperation by
reciprocal altruism, because both parties can profit from their
exchange over the long run (11). The ability to share know-how
through language thus may have been a major accelerant in the
evolution of cooperation because it gives humans both the
incentive and the means to cooperate. People can trade not only
goods but know-how and favors, and the negotiations are not
limited to what can be exchanged there and then but to goods and
favors transferred at widely separated times.
Language may foster cooperation, but it also depends on it,

because there is no advantage in sharing information with adversa-
ries (as we see in the expression “to be on speaking terms”). The
inherent synergies among language, intelligence, sociality, enhanced
paternal and grandmaternal investment, extended lives and child-
hoods, and diverse habitats and food sources suggest that these
features cohere as a characterization of the cognitive niche, with
enhancements in each serving as an additional selection pressure for
the others. As far as timing is concerned, we would expect that the
corresponding adaptations coevolved gradually, beginning with the
first hominid species that possessed some minimal combination of
preconditions (e.g., bipedality, group living, omnivory), increasing in
complexity through the lineage of species that showed signs of tool
use, cooperation, and anatomical adaptations to language, and
exploding in behaviorally modern H. sapiens.

Evaluating the Theory of the Cognitive Niche
The theory of the cognitive niche, I believe, has several advantages
as an explanation of the evolution of the human mind. It incorpo-
rates facts about the cognitive, affective, and linguistic mechanisms
discovered by modern scientific psychology rather than appealing to
vague, prescientific black boxes like “symbolic behavior” or “cul-
ture.” To be specific: the cognitive adaptations comprise the
“intuitive theories” of physics, biology, and psychology; the adap-
tations for cooperation comprise the moral emotions and mecha-
nisms for remembering individuals and their actions; the linguistic
adaptationscomprise thecombinatorial apparatusforgrammarand
the syntactic and phonological units that it manipulates.
The selection pressures that the theory invokes are straight-

forward and do not depend on some highly specific behavior (e.g.,
using projectile weapons, keeping track of wandering children) or
environment (e.g., a particular change in climate), none of which
werelikely to be in place over the millions of years in whichmodern
humans evolved their large brains and complex tools. Instead it
invokes the intrinsic advantages of know-how, cooperation, and
communication that we recognize uncontroversially in the con-
temporary world. Science and technology, organizations (such as
corporations, universities, armies, and governments), and com-
munication media (such as the press, mail, telephones, television,
radio, and the internet) are, respectively, just the exercise of cog-
nition, sociality, and language writ large, and they singly and jointly
enable the achievement of outcomes that would be impossible
without them. The theory of the cognitive niche simply extrap-
olates these advantages backward in time and scale.
Moreover, the theory requires no radical revision to evolu-

tionary theory: neither the teleology and creationism of Wallace,
nor mechanisms that are exotic, extreme, or invoked ad hoc for our
species. Although grammatical language is unique to humans, and
our intelligence and sociality are hyperdeveloped, it is not

uncommon for natural selection to favor unique or extreme traits,
such as the elephant’s trunk, the narwhal’s tusk, the whale’sbaleen,
the platypus’s duckbill, and the armadillo’s armor. Given the
undeniable practical advantages of reasoning, cooperation, and
communication, it seems superfluous, when explaining the evo-
lution of human mental mechanisms, to assign a primary role to
macromutations, exaptation, runaway sexual selection, group
selection, memetics, complexity theory, cultural evolution (other
than what we call “history”), or gene–culture coevolution (other
than the commonplace that the products of an …