Laland seeks to explain how culture evolved among humans, and humans alone, among all the animals on this planet. By culture he means, “the extensive accumulation of shared, learned knowledge, and iterative improvements in technology over time…. What singles out our species is an ability to pool our insights and knowledge, and build on each other’s solutions.” Humans exhibit a high degree of social learning, that is learning derived from copying others. Social learning is cheaper to acquire than trial and error discovery, but is vulnerable to acquiring out of date or not germane techniques or knowledge. Therefore, copying is selected for when asocial learning is costly, when there is uncertainty, and/or when there is dissatisfaction with the status quo. “Individuals could copy the majority behavior, copy the most prestigious individual, or copy the individual exhibiting the most successful behavior…. Individuals could be biased toward copying kin, familiar individuals, or dominants; they could prioritize learning from older, more experienced, or more successful animals; they could watch trends, monitor payoffs to others, or seek out rapidly spreading variants.” The choice structure for copying is nearly unlimited and can vary on a case by case basis. “An animal does not need to be smart to benefit from copying, because a lot of the smart decision making has already been done for it by the copied individuals who have already prefiltered their behavior…. What copying does do is reduce the rate at which behavioral variants are lost. That is because social learning generates multiple copies of a piece of knowledge or behavior, retained across the repertoires of several individuals, so that when an individual dies its knowledge need not die with it.” Along with the development of social learning, humans also developed theory of mind. “In order to imitate effectively, individuals must comprehend the goals and activities of the individual they copy. Comprehension requires the ability to consider alternative interpretations or viewpoints of external objects and to construct alternative scenarios of how to interact with them.” To effectively copy, it is necessary to step out of one’s self and take on the perspective of others. Sociality is another trait that might have been selected for amongst humans- people who are particularly observant of social cues and have tolerance for social groups, particularly kin.
The great human advance was in cumulative culture. “Humans incontrovertibly possess complex technology that no single individual could invent alone.” Teaching, alone among animals, is widespread across all communities of humans. “If teaching is to be favored, the skill taught should not be so simple that it is easy to be picked up without teaching [by simply copying], but at the same time, not so difficult that few individuals possess the skill and can pass it on,” stymying cultural retention. “Increments in the probability of teaching also occur when the costs of teaching are low or can be offset against the costs of provisioning, when teaching is highly accurate and effective in transmission, and when there is a strong degree of relatedness between tutor and pupil.” Language evolved as a mechanism to increase the efficiency of teaching. “Language is an adaptation, fashioned by natural selection to reduce the costs, increase the accuracy, and expand the domains of teaching.” It initially provided cues to help with imitation and skill acquisition. “Human language is unique, at least among extant species, because only humans constructed a sufficiently diverse, generative, and changeable cultural world that demanded talking about. Once our ancestors evolved a socially transmitted system of symbolic communication, other features of language, such as compositionality, came along for free…. Only in hominins did language, teaching, and cumulative culture coevolve in a runaway, autocatalytic process initiated by selection for strategic and high-fidelity social learning.”
Humans did not just evolve to take advantage of our environment, we shaped and transformed it to benefit our skillset. “The more an organism controls and regulates its environment and that of its offspring, the greater is the advantage of transmitting cultural information across generations…. Once started, cultural niche construction may also become autocatalytic, with greater culturally generated environmental regulation leading to increasing homogeneity of the social environment as experienced by old and young, which would favor further social learning from parents and other adults.” Humans evolved to better learn languages, but languages also evolved to be better learned. “Infant-directed speech [baby talk] is found in most, but possibly not all, societies, which suggests that it may be a widespread, socially learned tradition…. Children may appear preadapted to decipher the rules of syntax in part because languages have evolved rules that are easy to learn…. Transmission-chain experiments and mathematical models show how languages that are propagated culturally evolve in such a way as to maximize their own transmissibility, becoming easier to learn and more structured over time…. Humans were predisposed to be highly competent manipulators of strings of elements, because many of their ancestors’ tool-manufacturing and tool-using skills, extractive foraging methods, and food-processing techniques had required them to carry out precise sequences of actions.” Gene-culture coevolution has been documented in many regards. From right-handedness, to lactose tolerance, to salt retention, to fat storage, to sickle-cells, to the whites of the eyes, and to reduction of gut size, human culture has interacted with human genes to coevolve over time. “The rapid spread of cultural practice often leads quickly to maximally strong selection of the advantageous genetic variant, which rapidly increases its frequency. Cultural practices typically spread more quickly than genetic mutations, simply because cultural learning typically operates at faster rates than biological evolution.”
Human populations moving from hunter-gatherers to sedentary agriculturalists also marked the dawn of an explosion in cultural/genetic coevolution. With larger populations, and the resulting greater variations, biological evolution increased ever-faster and natural selection became stronger relative to genetic drift. Culture not only shaped human genetics, but that of domesticated animals as well. “Domestication…. selected for increased yields of animal products, such as milk, but also a variety of other traits, including lowered reactivity to environmental stimuli and a dependence on humans for survival and reproduction. The protection provided by corrals and pens, and selection of animals that were easy to manage, again modified the impact of natural selection on animal breeds…. Those plants and animals tended by humans became increasingly dependent on their keepers.” Some suggest that the earliest city-states in Mesopotamia were actually aggregations of irrigation systems from which defense and trading centers then rose around. This density was integral because “below certain population density thresholds not only is it difficult for new innovations to accumulate, but adaptive cultural knowledge may actually be lost.” Joseph Henrich gives the example of Tasmania, where cut off from mainland Australia, the native population lost skills such as the manufacture of fish nets, spears, and boomerangs over generations.
Writing was another key step of cultural transmission, as it allowed the memory and history of individuals to pass on beyond their lifetimes and increased the fidelity of the information retained. External memory extended beyond just the written word, however, to include architecture, painting, and dance. Humans extended their cooperation beyond close kin to include strangers in ever-enlarging circles of trust. This was achieved by societal norms. “At some juncture in our history, our ancestors began systematically to correct the behavior of the individuals they taught; in the process, they shifted their society away from reliance on mere conventions and toward governance through norms. People stopped illustrating a way to behave and began insisting on the way to behave…. Norms specify rules of social interaction too, including specification of how people should respond to norm violation. With the advent of norms, hominin social life effectively became transformed from simply living in groups to identifying with the group, abiding by its rules, and privileging in-group members…. For the mechanism of indirect reciprocity to work efficiently it needs gossip, from names to deeds and times and places, too.” By creating successful groups, norm enforcement could affect individual genetic traits. “Humans should be particularly adept at recognizing, representing, and adopting the local norms of their society, as well as notice, condemn, and punish violations of those norms… More “docile” individuals would be at an advantage, to the extent that they would be better placed to benefit from the society’s technologies and less vulnerable to exclusion or punishment. In turn, a population of more docile individuals could then permit the cultural evolution of more sophisticated and effective norms, and allow groups to maintain more reliable cooperation. A similar mechanism could have favored a tendency of individuals to feel shame or guilt when they violate a social norm.”
Laland makes an intriguing case for how culture and biology coevolved among humans. Through a mechanism that started with copying, moved to active teaching, then to language, and the written word, humans were able to build on past gains, which changed the physiological makeup of our brains and bodies, which further transformed our culture in a spiral that alone among animals allowed for the accumulation of knowledge and skillsets that would be impossible for any one human to master in a single lifetime.
No comments:
Post a Comment