| The Primate Mental Climate, by Anthony Peter Iannini, 1999 |
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Essay Overview: An essay that attempts to draw a simple analogy between the social evolutionary environment of primates and a fictional thermal environment in order to clarify a point about increasing pressures.
My goal is to draw an analogy between thermal climate change and adaptation and social ‘climate’ change and adaptation. I will discuss the change in natural social climate that occurred during primate evolution and the drastic social climate change that occurs during primate transplantation into captivity; in other words, transplantation into a human social climate. The pressures leading to the evolution of the human mind (higher cognitive functions) will be central to my discussion.
Although evolution is a highly complex and enigmatic process, it is possible to conceptually demonstrate how an organism’s environment will affect its evolution. If a sufficiently large grouping of a species that has adapted to a sufficiently warm climate is transplanted and placed in a sufficiently cold climate, one of two outcomes will result. The first possible result would be the death of the group of the species.
The second possible result would be adaptation, or a change in the genotype and phenotype of the species to survive the sufficiently colder climate. This would all be done in an environment where significant migration would be impossible, and random mating occurs. In this case, evolution can be made somewhat simple. Place a species in a severely new environment, and it will either die or adapt over time.
The wooly mammoth grew course, robust hair because it was exposed to a cold environment. We can imagine that if the elephant species had not developed this adaptation to the cold environment, it would have perished in the absence of migratory possibilities. While the above illustration seems somewhat outside the topic of primate mental evolution, it will serve to set the conceptual foundation on which to continue my analogy.
The above illustration uses thermal climate as the force involved in evolutionary adaptive change. But, something else changed in the primate environment that caused the divergence in lineage approximately six million years ago that caused gorillas and chimpanzees to continue along one path, and humans another (Mithen, 1996, p. 17).
The change in climate surrounding the evolution of the human mind was not thermal in nature, as in the opening illustration, but rather a change in social climate. In a sense, the primates along one evolutionary lineage were beginning an intercommunal divergence from others in their species. It was a change in the immediate environment; among the members of the species, in their actions, and their cognitive mechanisms.
What caused this new environment to emerge? There are a number of factors that seem to play a role in determining why a social climate change began; a change that would require the members of the primate species to begin competing for the greatest adaptive advantage over others in their species. Perhaps the most important physiological change was the emergence of bipedalism, which freed up the arms and hands for communication and the rudiments of tool manipulation.
As Michael Corballis writes, “The most decisive event that sent the early hominids on the path toward humanity was their assumption of the upright stance... Bipedalism freed the hands for other activities... leading to the manufacture of tools, language, and perhaps a restructuring of thought” (Corballis, 1991, p. 52). Many anthropologists have found that the shift in posture seems to be one of the most decisive factors in the later development of the primate evolutionary lineage and the ensuing mental developments.
“Upright posture, bipedalism, and brain development seem to be connected, parallel tendencies in the anthropoid primates. If we wish to explain the emerging powers of the brain for rational thought, therefore, the conditions and functions of these characteristics deserve some attention” (Wilson, Peter J. 1983, p. 21). With this ‘spark’ of further communicative and manipulative ability, the mental progression towards higher cognitive functions was well on its way towards something different and formerly unseen in terrestrial evolution.
The topic of what caused the rather aggressive continuation of primate mental evolution has sprouted a number of debates in recent years. The argument has mainly diverged among two aspects of primate life that seem to force new cognitive capabilities and specializations; areas which would require a shift towards “higher” mental functions. The first of these two areas is the ability to use and/or make tools. The second of these areas is social interaction or social manipulation.
Primate tool use is diverse, and found in a variety of great apes. However, tool creation is limited to only a few examples of rudimentary manipulation of sticks, stones, and bones to make objects that only require a level or two of planning (Tomasello & Call, 1997, p. 71). While we should not overlook these interesting capacities to make and even, in some situations, create tools, there are several problems with viewing tools as the central factor in continuing primate mental evolution that will become apparent when the social interaction interpretation is examined.
In terms of social interaction, primates must “balance a diverse range of competitive and co-operative options. Individuals may compete not only over mates, but (for example) over feeding resources, sleeping sites, location in the group...allies, grooming partners, playmates and access to infants, and...agnostic encounters.” (Byrne & Whiten, 1988, p.4). From the observations of researchers, we know that primate social interactions are diverse, complex, and very time consuming.
Which aspect of primate life wins as the decisive factor for continuing their evolutionary mental development? There are a number of factors that are certain. First, primate social life is almost a constant pressure, whereas tool use and creation is highly infrequent in comparison. This would mean, from an evolutionary standpoint, social pressures would be more of a determining factor in adaptive pressures.
Ian Tattersall writes, “There’s no doubt, then, that as we move from lemurs, to monkeys, to apes, and finally to humans, the immediate social settings in which these creatures live, move, and have their beings become more complex: that, in effect, their social environment occupies an increasingly large proportion of their total environment” (Tattersall, 1998, p. 43). Also, social interaction among primate groups seems to be more complex, encompassing diverse possibilities and many more levels of intentionality than tool use.
The social climate was certainly becoming a more important factor with time for the primates. In terms of the thermal climate analogy drawn earlier, if we slightly lower the temperature in the environment of a species adapted to warmth, then temperature will play only a slight importance in their adaptive development.
However, if we lower the temperature more and more, then the species will be forced to change, perhaps radically, in order to adapt in the new environment. In this way, the social climate was shifting in and around the primates, with causes arising from their own interaction, evolutionary developments, and new mental capacities. Their radical change would not be the external, wooly coat of the mammoth, but the internal, nearly triple sized brain (compared to other primates) that eventually facilitated the higher functions of the modern human mind (Lumsden, 1983, 102-103).
Consciousness as an adaptive trait could not have come from tool use or manipulation. Only in trying to predict and manipulate the actions of conspecifics could consciousness arise as an adaptive mechanism. As asserted by Nicholas Humphrey (1984, 1992) “the biological function of consciousness is to explore our own minds in order to have a model for the mind of another individual.”
This simple yet elegant understanding of the adaptive origin of consciousness makes perfect conceptual sense. If male primate X wants to best understand the intentions, desires, or probable actions of male primate Y, the best course of action for primate X is to examine what he himself would do in such a situation. The use of oneself as a good estimation for the intentions, desires, or probable actions of others seems highly beneficial, in that such actions lead to a greater ability to manipulate the conspecific environment. And, if consciousness is an advantage (which it certainly seems to be), it would have been selected for and inherited in primate groups.
Most basically, interpretation is the ability to understand the goals of others. Why it seems likely to have evolved is somewhat more complex. Bogdan (1997, p. 29) writes that “...interpretation evolves as a specialized form of cognition because goal-pursuing organisms, operating as independent and versatile agents, interact with other such agents in social patterns where the interaction among their goals ultimately affects the viability and fertility of the interactors.”
It seems as though interpretation is a result of consciousness, which allows organisms to look inward in order to make judgements about, or interpret, the motives and actions of others. Without the pressure of the social climate, interpretation would have been useless in primate evolution. Without such pressures, consciousness and the preceding interpretational skills of the higher primates would have never been selected for amongst conspecifics. The wooly mammoth developed a thick fur coat because of its environment, while humans developed consciousness and interpretation because of theirs.
Some interesting things happen when the higher primates are taken from their natural habitat and transplanted into captivity. Conceptually, the human social climate is the result of a gradual change over millions of years from the primate social climate. For the ape in captivity, the change in social climate is dramatic.
And it is this change that allows for apes to display what Gould & Vrba (1982) have defined as exaptations, or those functions that do not seem to have been shaped by natural selection. “One of the most interesting facts of primate behaviors is that some species engage in complex cognitive abilities in captivity that they do not engage in in the wild” (Call and Tomasello, 1996, p. 390).
The specific abilities of primates in captivity include a number of capacities that are rarely, if ever, seen in the wild. “...it appears that the chimpanzee can develop competencies for learning meanings of arbitrary symbols, for comprehending syntax of human speech, and for counting, for example. None of these competencies have obvious analogues of homologues that are used adaptively in the field” (Rumbaugh & Savage-Rumbaugh, 1992, p. 302). These relatively advanced cognitive abilities force the question, what exactly does social climate do to the primate mind to allow for such cognitive variability?
The answer to this perplexing question may lie in a critical period during the primate life; namely childhood. According to Savage-Rumbaugh (1992, p. 302) “It is suggested that the developmental structures for cognition in apes and humans are quite plastic and that their organization is particularly sensitive to the structured and recurring systems of stimulation during infancy.”
While there must be a limit to the cognitive variability that can be found in the primate mind, it is obvious from apes in captivity that the period of brain development plays an important role in developing cognitive abilities. “It is generally accepted that early rearing and environmental enrichment can enhance the learning abilities of not just primates (Davenport, 1973), but mammals in general.”
Kanzi, the infant bonobo raised from infancy in captivity, performed at a much higher level of competency and learning than his mother Matata, who was brought into captivity after five years of feral living. And, Kanzi was only an observational learner during his time in captivity, independently observing the training that his mother was receiving (Rumbaugh & Savage-Rumbaugh, 1992, p. 302).
We can infer from this and other examples like it, that something very important happens during early brain development in primates that is directly related to the social climate. An interesting fact is the varying length of child development in different primate species. A. Jolly (1972, 215) provides the following comparisons among primates for length of infancy:
Lemur |
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6 months |
Macaque |
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18 months |
Gibbon |
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2 years |
Chimpanzee |
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3 years |
Human |
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6 years |
It appears as though there is a correlation between what we see apes doing in captivity, and the period of primate development. As we move towards humans in the primate evolutionary lineage, the developmental period becomes more important and plays a greater role in how the mental capacities are expressed. This expression seems to be directly related to the social climate in which the development occurs.
As Charles Lumsden writes, “The genes and culture are inseverably linked. Changes in one inevitably force changes in the other, resulting in what we have termed gene-culture coevolution. This uniquely human process is an enchanted circle into which the species has been drawn and will travel for the rest of its existence...” (1983, 117-18). We see that the genetic changes in primates are directly related to their social climate, and in turn, changes in primate social climate are directly related to their genes.
The social climate has played a crucial role in the emergence of many higher cognitive functions in humans and other primates. And, the rather dramatic effects of social climate can be observed when we transplant primates into captivity, thereby introducing them to new pressures. When we observe mental capacities and child development, we again see social climate as the determining factor. The wooly mammoths were increasingly exposed to cold, and adapted. Humans, on the other hand, were increasingly exposed to each other, and adapted
Bibliography:
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