Comments welcome
George W. Grace
University of Hawaii

Reflections on the evolution of human language:

1. Robin Dunbar’s Social Bonding Hypothesis

I suppose the main reason for my being interested in the question of how language might have evolved is the hope that pursuing it might lead us to a new perspective on what language really is. And I think that is needed. For one thing, I feel the role of analytic (as compared to holistic) processing has been greatly exaggerated.

It appears to me that writings by some linguists on the subject of language evolution have persuaded many laypersons that the key development to be explained is syntax, and that syntax requires an innate quasi-mathematical brain “module”. I think this conclusion rests on two very doubtful presuppositions: (1) that speech “processing” involves a lot more calculation, and a lot less simple recognition (i.e., is a lot more analytic and a lot less holistic), than is actually the case, and (2) that the more complex syntactic structures could not have evolved gradually from simpler ones (which could not themselves have evolved from unstructured signals). A broader-based approach to the evolution of language might help get us out of this bind.

In their book, Human evolutionary psychology, Louise Barrett, Robin Dunbar, and John Lycett (Barrett et al 2002) point out that in current approaches to the evolution of language,

the conventional spotlight has been on how language facilitates the exchange of information rather than on why we have language at all. (2002: 323)
They add,
This inevitably means a focus on grammar and the way grammar aids in the coding and comprehension of thoughts” (ibid.)
and fails
“to address the larger evolutionary question as to why we need to exchange our thoughts in this way. (ibid.)

That question is indeed a fundamental one. How did humans come to have language? What were the factors in the environment of our ancestors that selected for the first steps in the direction of language--factors that were lacking from the environments of their closest relatives? And what was the nature of these first steps?

Their preferred answer to the first of these questions is found in Robin Dunbar’s Social Bonding Hypothesis (or “Gossip Hypothesis”, as they label it), which was introduced in Dunbar 1996. At this point, that hypothesis seems very plausible to me--more plausible than any other that I’ve seen.

Probably one reason that I find it promising is that it has human language evolving out of communication concerning social relationships. I have long been impressed by the work of Gregory Bateson, who studied communication in a number of mammal species. He repeatedly emphasized that their communication was always about relationships. According to Bateson,

What was extraordinary--the great new thing--in the evolution of human language was... the discovery of how to be specific about something other than relationship. (1972: 367, my emphasis)
And he adds,
Indeed, this discovery, though it has been achieved, has scarcely affected the behavior even of human beings. (ibid.)
Dunbar sums up his social bonding hypothesis as follows:
…that language evolved among humans to replace social grooming because the grooming time required by our large groups made impossible demands on our time. Language, I argue, evolved to fill the gap because it allows us to use the time we have available for social interaction more efficiently. (1996:192).
I’ll try to clarify a few points:

1. “Social grooming”. What he refers to here as “social grooming” is a common practice of primates. They “spend hours each day ruffling through each other’s fur, removing bits of loose skin or burrs caught in the fine hairs” (Dunbar 1996: 67)(1). The frequency with which any two individuals groom each other appears to be a reliable index of the closeness of the social bond between them--that is, the extent to which each can count on the other for support.

2. Why are close social bonds important? Dunbar explains that as group size grows, the individual is increasingly surrounded by competitors jockeying for social dominance and superior access to resources. The individual’s defense against this threat is to acquire allies, and the cement that secures and maintains such alliances is mutual grooming.

3. Why did those in our ancestral line live in larger groups than other primate species in the first place? His answer: Large groups offer more protection against predators. When early hominids moved out of the forests, they exposed themselves to greater risks from predators. As Dunbar explains,

…primates in general exhibit two responses to increased predation: they grow physically bigger and they increase the size of their groups. Our ancestors appear to have done both. (1996:110),
4. Why do larger groups require more grooming time? A survey of the available information on various primate species showed that an increase in the size of groups correlates with an increase in the size of the alliances (“grooming cliques”). There is also a, perhaps significant, correlation of the size of both with neocortex size.

As the size of an individual’s alliances increased, the grooming time required to maintain them would have gradually increased to the point of exceeding the time available. Transferring functions of grooming to vocal signals offers the obvious advantage of bonding larger alliances since one can “groom” with several others at the same time. The hypothesis, then, is that vocalizations came to assume a greater part of the burden of keeping alliance members in touch with one another--providing one’s allies with some information about where one is and what one is doing. They thus assumed an expanding role as a kind of “vocal grooming”.

5. Where does the idea that vocal signals could play the same role as grooming come from? Many primate species already make extensive use of calls that maintain contact between alliance members. According to Dunbar’s hypothesis, it is from these “contact calls”--which he describes (1996:115) as functioning in present-day monkeys and apes as “a kind of grooming-at-a-distance”--that language evolved.

But information of one’s whereabouts is a long way from the kind of information that would have to be developed to have anything approaching language as we know it. To quote Dunbar further:

Eventually, even this form of communication would have exhausted its capacity to bond groups. A more efficient mechanism for bonding was needed to allow group size to continue its upward drift. At this point, the vocalizations began to acquire meaning. But the content was largely social: gossip had arrived.
This need not have involved any dramatic change, for as the studies by Seyfarth and Cheney have shown, primate vocalizations are already capable of conveying a great deal of social information and commentary. (1996: 115)
(That quotation should explain why Dunbar’s hypothesis this is often referred to as “the gossip hypothesis”.)

It is true that the contact calls of primates often carry information beyond the mere location of the caller. The work of Dorothy L. Cheney and Robert M. Seyfarth on the information conveyed by the vocalizations of vervet monkeys has been particularly eye-opening. Moreover, it has become clear that our understanding of the significance of variations in the calls of most primate species is still at a very primitive stage, and that contrasts that carry significant information are sometimes difficult for humans even to perceive.

Dunbar’s summation: Dunbar presents the following summation of his hypothesis:

The central argument revolves around four key points: (1) among primates, social group size appears to be limited by the size of the species' neocortex; (2) the size of human social networks appears to be limited for similar reasons to a value of around 150; (3) the time devoted to social grooming by primates is directly related to group size because it plays a crucial role in bonding groups; and finally, (4) it is suggested that language evolved among humans to replace social grooming because the grooming time required by our large groups made impossible demands on our time. Language, I argue, evolved to fill the gap because it allows us to use the time we have available for social interaction more efficiently. (1996: 192)
Remaining questions:
As I said above, this hypothesis seems to be a very promising place to start. However, I still have questions about each of the two main steps in his proposed sequence.

1. How could vocalizations play the same role that grooming does? Being groomed is reported to be a very pleasurable experience. As Dunbar points out:

In fact, we now know that grooming stimulates the production of the body’s natural opiates, the endorphins; in effect, being groomed produces mildly narcotic effects. (1996: 36)
And as he acknowledges:
The problem here is that vocalizations are just, well, vocalizations. They don't have the same opiate-releasing properties as grooming. (1996: 190)
His proposed solution:
However, suppose that as language develops, signals associated with language themselves begin to stimulate opiate production. Smiling, and particularly, laughing do just this, and this may well explain why smiling and laughing are such important components of conversation. (1996: 191)
This would presumably require us to imagine that the early stages in the transition from contact calls to language were represented by something quite different from sober-faced exchanges of information. On the contrary, we should perhaps think more of smile- and/or laughter-filled interactions. This may in fact suggest that the early stages of language were closely allied with play (which is also more developed in larger-brained species)--certainly an interesting suggestion that deserves to be pursued further.

2. How did our ancestors make the step from simple contact calls to vocal signals that communicated other kinds of information? Dunbar’s answer to this is not an explanation of how the step was accomplished but rather a description of the particular kinds of advantage it might have afforded in that context. He suggests ways in which the social-bonding function of a system of vocalizations could itself benefit by evolving the ability to carry additional information. He points out that it could have offered additional advantages to alliance-formation if it permitted information to be communicated about potential allies. He talks in particular about the problem of sorting out potentially reliable allies from “free-riders”--individuals who habitually accept favors without reciprocating.

Language, he points out,

allows you to say a great deal about yourself, your likes and dislikes, the kind of person you are; it also allows you to convey in numerous subtle ways something about your reliability as an ally or friend.(1996:78)
Language has an additional benefit invaluable in these circumstances. It allows us to exchange information about other people, so short-circuiting the laborious process of finding out how they behave. For monkeys and apes, all this has to be done by direct observation. (1996: 79)
That such information could have had survival value seems reasonable enough. It is easy to believe that natural selection might have immediately favored individuals who had made even the first limited step in this direction.

What was the first step? Nowak et al (2000) focus on the “evolution of syntactic communication”, which they conceive as the change from signals that refer to whole situations or events to signals composed of two elements (essentially a noun and a verb). In their words:

Non-syntactic communication uses words for events, whereas syntactic communication uses words for objects and actions. (2000: 496),
Their argument is that
the crucial step that guided the transition from non-syntactic to syntactic communication was an increase in the number of relevant events that could be referred to. (2000: 497)
In other words, “syntactic communication” makes the use of a much larger number of signals feasible. Therefore, when the number of distinct signals needed passed a certain critical point, syntactic communication could be expected to evolve.

Their proposal doesn’t require anything dramatic like a mutation (although, of course, natural selection would be expected to favor the individuals who were best equipped to exploit the new syntactic communication).

In fact, they suggest that the very simple syntactic system they propose could have been expanded by similar gradual steps when these in turn became advantageous.

If this is so, if the grammatical complexities of contemporary languages could have evolved in such an undramatic way, then the failure of Dunbar’s proposal to explain what the first crucial step was may not fairly be regarded as a serious defect.(2)


1. I’ve always understood that the great apes (like humans) have hair rather than fur, but that’s only a technicality.

2. As to the nature of the first step, there’s another point made by Bateson that might be relevant here. He says,

In general, the discourse of animals is concerned with relationship either between self and other or self and environment. In neither case is it necessary to identify the relata. (1972:141)
This seems to suggest that the first step might have been one that identified relata in a minimal way. That sounds more like some kind of 3rd person marker than like an immediate leap to full-fledged nouns. For example, it might involve adding some pronominal indication of 3rd person subjects and/or objects (or more likely I would have guessed, 3rd person absolutives--as opposed to ergatives).


Barrett, Louise, Robin Dunbar, and John Lycett. 2002. Human evolutionary psychology. Princeton: Princeton University Press.

Bateson, Gregory. 1972. Steps to an ecology of mind. New York: Ballantine Books.

Dunbar, Robin. 1996. Grooming, gossip, and the evolution of language. Cambridge MA: Harvard University Press.

Nowak, Martin A., Joshua B. Plotkin, and Vincent A. A. Jansen. 2000. The evolution of syntactic communication. Nature 404: 495-98.

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