This being St. Valentine's day, I thought I'd bring out some of the theories proposed over the years about the relationship of courtship and mating to the evolution of language. Charles Darwin thought that language evolved out of love songs, at least partly. More recently, Terence Deacon has argued that language evolved so as to permit marriage contracts to be expressed, negotiated and socially accepted. (There are many other interesting stories about language evolution, but this is February 14, after all.)
In The Descent of Man (Chapter 3) Darwin suggested that
"primeval man, or rather some early progenitor of man, probably first used his voice in producing true musical cadences, that is in singing, as do some of the gibbon-apes at the present day; and we may conclude from a widely-spread analogy, that this power would have been especially exerted during the courtship of the sexes,- would have expressed various emotions, such as love, jealousy, triumph,- and would have served as a challenge to rivals." (Descent of Man, Chapter 3).
He went on to say (Chapter 19, "Secondary Sexual Characters of Man") that
"We must suppose that the rhythms and cadences of oratory are derived from previously developed musical powers. We can thus understand how it is that music, dancing, song, and poetry are such very ancient arts. We may go even further than this, and, as remarked in a former chapter, believe that musical sounds afforded one of the bases for the development of language.
... Mr. Spencer comes to an exactly opposite conclusion to that at which I have arrived. He concludes, as did Diderot formerly, that the cadences used in emotional speech afford the foundation from which music has been developed; whilst I conclude that musical notes and rhythm were first acquired by the male or female progenitors of mankind for the sake of charming the opposite sex. ...
... [I]t appears probable that the progenitors of man, either the males or females or both sexes, before acquiring the power of expressing their mutual love in articulate language, endeavoured to charm each other with musical notes and rhythm. ... [W]e have no means of judging whether the habit of singing was first acquired by our male or female ancestors. Women are generally thought to possess sweeter voices than men, and as far as this serves as any guide, we may infer that they first acquired musical powers in order to attract the other sex. But if so, this must have occurred long ago, before our ancestors had become sufficiently human to treat and value their women merely as useful slaves."
More recently, Terence Deacon argued in his 1997 book The Symbolic Species that human language evolved not as an mechanism of courtship but rather as a means for establishing socially-recognized promises of sexual exclusivity. [What follows is a summary reproduced from lectures notes I wrote a few years ago for an introductory linguistics course].
Deacon's argument is a complex one, depending on a number of results from ethology and other allied fields.
He argues that the key point is a shift to a symbolic mode of communication, in which new linguistic tokens (i.e. words) can be created with an arbitrary relation to their meanings. He stresses that the first steps in developing symbolic communication look very difficult for a non-linguistic species, helping us to understand why no non-human species has gone very far down that road:
Even a small, inefficient, and inflexible symbol system is very difficult to acquire, depends on significant external social support in order to be learned, and forces one to employ very counterintuitive learning strategies that may interfere with most nonsymbolic learning processes. The first symbol systems were also likely fragile modes of communication: difficult to learn, inefficient, slow, inflexible, and probably applied to a very limited communicative domain. . . . Neurologically and semiotically, symbolic abilities do not necessarily represent more efficient communication, but instead represent a radical shift in communicative strategy. It is this shift, not any improvements, that we eventually need to explain.
As a rule, he argues, significant changes in communicative systems in other species occur "in the context of intense sexual selection."
It is at the point in the life cycle where choice of mate takes place that evolutionary theory predicts we should find the greatest elaboration of communicative behaviors and psychological mechanisms in both pair-bonding species and polygynous species, though the communicators and the messages may differ significantly in these two extremes. Between these extremes there are many more complex mixtures of reproductive social arrangements that add new possibilities and uncertainties, and thus further intensify selection on the production and assessment of signals.
Deacon then points out that human mating arrangments, though diverse across societies, share some characteristics that make our species nearly unique: "cooperative, mixed-sex social groups, with significant male care and provisioning of offspring, and relatively stable patterns of reproductive exclusion, mostly in the form of monogamous relationships." According to Deacon, "reproductive pairing is not found in exactly this pattern in any other species." The reason this pattern is not found, he argues, is that it's a recipe for sociosexual disaster: "the combination of provisioning and social cooperation produces a highly volatile social structure that is highly susceptible to disintegration."
In evolutionary terms, a male who tends to invest significant time and energy in caring for and providing food for an infant must have a high probability of being its father, otherwise his expenditure of time and energy will benefit the genes of another male. As a result, indiscriminate protection and provisioning of infants will not persist in a social group when there are other reproducing males around who do not provision, but instead direct all their efforts towards copulation.
These tensions get worse if males and females spend a lot of their time apart, as necessarily happens if males are out hunting and scavenging while females are gathering plants with children in tow. "Hunting and provisioning go together, but they produce an inevitable evolutionary tension that is inherently unstable, especially in the context of group living. Besides ourselves, only social carnivores seem to live this way."
Carnivores that engage in cooperative group hunting include wild dogs, wolves, hyenas, lions and meercats. All such creatures exhibit particular ecological and reproductive patterns that defuse the resulting evolutionary tension. Among lions, provisioning takes place among a "pride" of closely-related females (sisters, aunts etc.). One, two or rarely three male lions take over a pride and guard it against other males -- who will try to kill the cubs to bring the females into estrus -- but do not provide food. Among wild dogs and wolves, the cooperative hunting pack includes both males and females, and they provision both pups and a nursing mother. However, in a given pack there is usually only one reproducing female, who is typically the mother of many of the hunters. Other females are kept from becoming sexually receptive by social pressures and perhaps pheromones. There is usually also only one reproductively active male in a pack.
The typical human pattern -- with many reproductively active males and females living in a group while maintaining patterns of sexual exclusivity, and with male provisioning of children although mated males and females spend considerable time apart -- is never found among the social carnivores.
Deacon suggests that this background helps to explain why the evolution of systematic hunting as a major food source for our hominid ancestors posed a difficult problem in social engineering.
The acquisition and provisioning of meat clearly would be a better strategy for surviving seasonal shortages of more typical foods than shifting to nutrient-poor diets of pith, bark, and poor-quality leaves, as do modern chimpanzees. But this is only possible if there is a way to overcome the sexual competition associated with paternity uncertainty. The dilemma can be summarized as follows: males must hunt cooperatively to be successful hunters; females cannot hunt because of their ongoing reproductive burdens; and yet hunted meat must get to thoese females least able to gain access to it directly (those with young), if it is to be critical subsistence food. It must come from males, but it will not be provided in any reliable way unless there is significant assurance that the provisioning is likely to be of reproductive value to the provider. Females must have some guarantee of access to meat for their offspring. For this to evolve, males must maintain constant pair-bonded relationships, and yet for this to evolve, males must have some guarantee that they are provisioning their own progeny. So the socio-ecolgogical problem posed by the transition to a meat-supplemented subsistence strategy is that it cannot be utilized without a social structure which guarantees unambiguous and exclusive mating and is sufficiently egalitarian to sustain cooperation via shared or parallel reproductive interests.
Deacon argues that this problem required -- or at least invited -- a solution mediated by symbols.
[C]ertain things cannot be represented wthout symbols. . . . Although there is a vast universe of objects and relationships susceptible to nonsymbolic representation, indeed, anything that can be present to the senses, this does not include abstract or otherwise intangible objects of reference. This categorical limitation is the link between the anomalous form of communication that evolved in humans and the anomalous context of human social behavior.
For hunting and provisioning to co-exist in large groups of reproductively active hominids, Deacon argues, it was necessary to establish a certain sort of social contract. If this contract can be establishing and maintained, then everyone is better off. However, it will not work until nearly everyone observes the terms and also enforces observance among others.
Essentially, each individual has to give up potential access to most possible mates so that others may have access to them, for a similar sacrifice in return.
Accomplishing this requires two things. First, you have to establish a shared understanding of who is bonded with whom. According to Deacon, "this information can only be given expression symbolically", because it "is a prescription for future behaviors," not just a memory or an index of past behavior, or an indication of current social status or reproductive state, or even a prediction of probably future behavior.
The pair-bonding relationship in the human lineage is essentially a . . . set of promises that must be made public. These . . . implicitly determine which future behaviors are allowed and not allowed; that is, which are defined as cheating and may result in retaliation.
Second, you have to get everyone else that might be involved to agree not to cheat, and to help protect against cheating.
For a male to determine he has . . . paternity certainty, requires that other males also provide some assurance of their future sexual conduct. Similarly, for a female to be able to give up soliciting provisioning from multiple males, she needs to be sure that she can rely on at least one individual male who is not obligated to other females to the extent that he cannot provide her with sufficient resources.
A marriage contract is a social contract, not just an agreement between the bonded pair. It is typical in human societies for the social group as a whole to play an active part in maintaining sexual exclusivity between individuals; this is something that happens in no other species. Deacon argues that it happens among humans because all members of the group "are party to the social arrangement, and have something to lose if one individual takes advantage of an uncondoned sexual opportunity."
Deacon is less clear about the first steps in the process of establishing such social contracts. He suggests that the ability of apes to acquire limited symbolic abilities in laboratory settings give us an indication of what our species' symbolic beginnings might have been.
In a word, the answer is ritual. Indeed, ritual is still a central component of symbolic "education" in modern human societies, though we are seldom aware of its modern role because of the subtle way it is woven into the fabric of society. The problem for symbol discovery is to shift attention from the concrete to the abstract; from separate indexical links between signs and objects to an organized set of relations between signs. In order to bring the logic of token-token relationships to the fore, a high degree of redundancy is important. This was demonstrated in the experiments with the chimpanzees Sherman and Austin. It was found that getting them to repeat by rote a large number of errorless trials in combining lexigrams enabled them to make the transition from explicit and concrete sign-object associations to implicit sign-sign associations. Repetition of the same set of actions with the same set of objects over and over again in a ritual performance is often used for a similar purpose in modern human societies. Repetition can render the individual details for some performance automatic and minimally conscious, while at the same time the emotional intensity induced by group participation can help focus attention on other aspects of the objects and actions involved. In a ritual frenzy, one can be induced to see everyday activities and objects in a very different light.
To sum up: Deacon thinks that early hominids developed symbolic communication as a way to establish social contracts permitting stable family and group structures, which otherwise would not have permitted hunting and scavenging for meat as a systematic source of supplemental food during times of drought. This set the state for nearly two million years of evolutionary adaption for improved symbolic communication, probably due to sexual selection (crudely, females preferred males who could make more convincing promises).
Posted by Mark Liberman at February 14, 2004 01:57 PM