User:Origins3F03/Cultural Evolution in Humans

The complexity of human behavior relies not only on hard-wired instinctual processes, but also on mechanisms of learning that drive cultural evolution (see Dual Inheritance Theory). The learned behavioral repertoire in humans is transmitted from individual to individual within a social network through social learning. In essence, cultural evolution serves as an adaptive mechanism that results in increased fitness within particular environments. The sophisticated cognitive processes that govern human learning are unique among animal groups, and presumably correlated with the evolution of the human brain.

Culture
A culture refers to the information or sum of traditions individuals acquire through group learning. As a result of its dependence on a society for transmission, cultures may differ among groups. Unlike other animals, humans perform a large range of behaviours that rely heavily upon group learning. Culture consists of nongenetic heritable traits among populations and requires overlapping generations for its transmission. Cultural transmission can be compared with genetic transmission as shown in table 1. Clearly, culture has a large influence in shaping the human species. Many human traits, such as religious behaviours and language, are thought to have emerged from cultural transmission. Table 1: Genetic Transmission compared to Cultural Transmission

Humans learn either individually or through groups. The survival and reproduction of a species is strongly dependent on the information the species has regarding the environment. When this information is not available innately, it can be acquired through individual and cultural learning. For instance, to decide whether or not something is edible, we can use our innate abilities as humans, if they exist, or we can decide through individual learning, by tasting, or through cultural learning, by observing the behaviour of others. Thus, there are three distinct methods by which humans can obtain information: innate mechanisms, individual learning, and cultural learning. Innate behaviors refer to hardwired responses that emerge from genetic information. Individual learning occurs when organisms acquire information by themselves through innovation or via trial-and-error within their lifetimes. Cultural learning takes place when information is obtained by observing and imitating the behaviour of others. The incidence and performance level of animals that obtain information through group learning differ among species. Humans have a strong “learning capacity”, or amount of information organisms learn, and a high “learning level”, or accuracy and effectiveness of learning. Relative to other species, humans are capable of obtaining a large degree of information and using it to their advantage at a greater rate and to a greater extend than others.

Individual Learning
The evolution of learning strategies came into play when hardwired behavioural responses were unable to compensate for environmental fluctuations. When the environmental stability is sufficiently high, there is a great dependency on innate behavioural responses. However, when the environmental stability is intermediate, there is an increased dependency on cultural learning. When the environmental stability is sufficiently low, there is an increased dependency on individual learning. As a result, the contribution of genetic information to fitness fluctuates along with environmental stability, ultimately resulting in changes in adaptive learning techniques. In other words, as the fitness decreases due to a slow decrease in environmental stability, both individual and cultural learning capacities increase. Under non-stable environmental conditions, individual and cultural learning can become adaptive. It must be noted, however, that individual learning is necessary but not sufficient for human cultural evolution. Cultural evolution ultimately requires cultural learning, a type of adaptive social learning. Essentially, individual learning acts as an initiator of cultural evolution.

Nakahashi Models
The effects of environmental change on learning strategies were best modeled by Nakahashi. These models have been observed in humans as well as non-human species.

Model 1

The first model demonstrated a decrease in individual learning capacity as cultural learning capacity increased due to an increase in environmental stability. The individuals in this model acquire less information individually as a result of an increase in culturally acquired information. The probability of learning valuable information through cultural learning is higher than that of learning information through individual learning when the environmental stability is increased.

Model 2

In this model, Nakahashi demonstrated that individual learning capacity decreases as cultural learning capacity increases due to an increase in cultural learning levels. As the accuracy and efficiency of cultural learning increases, the amount of cultural learning occurring is greater in comparison to the amount of individual learning. In this model, the level of cultural learning increases alongside the environmental stability. Using this model, Nakahashi also illustrated that the individual and cultural learning capacities increase as the individual learning level increases. This is due to the fact that the frequency of beneficial information increases when individual learning is high, which in turn causes cultural learning to be effective as well.

Evidence

Model 2 can be witnessed among different species of primates where there is a high learning level that allows the species to acquire large amounts of information both individually and culturally, causing a positive correlation between individual and cultural learning. The evidence supporting this model is observed when comparing individual and cultural learning behaviours in primates to brain volumes as well as to the species' learning levels.

By applying these models to human evolution, we are able to witness a positive correlation between individual and cultural learning and the impact that learning had on our species. Humans branched off approximately 5-6 million years ago from the chimpanzees. The early human ancestors and chimpanzees had about the same brain size of 300-400 cc. Up to 2.5 million years ago, the brain size difference was only 100 cc. From 2.5 million years ago to the present time, the brain size enlarged to about 1000 cc after the genus Homo emerged. This growth is theorized to have resulted in the evolution of high levels of learning in the genus Homo. According to this theory, as the ancestors of the genus Homo underwent drastic environmental changes, their learning abilities adapted, and this resulted in the enlargement of the brain. In turn, the enlargement of the brain improved learning abilities. Paleoclimatic evidence supports the hypothesis of a drastic climate change that resulted in a drier African climate about 2-3 million years ago. At this time, there were two new hominid lineages, the “robust” australopithecines and the genus Homo. The robust australopithecines had large cheek teeth and strong jaw musculature which allowed processing of coarse vegetable matter and food. Their teeth and jaws were suited for the food available in drier climates. On the other hand, the early Homo had gracile teeth and a weaker jaw, which were not well adapted for the food available in such dry environmental conditions.

The early Homo had a baseline fitness that was thought to be smaller than that of the robust australopithecines. Consequently, the genus Homo had to rely on increasing their fitness for survival and reproduction by adapting through learning, which then resulted in an enlargement of the brain. The robust australopithecines, in contrast, had the genetic make up necessary to compensate for the environmental changes. Homo sapiens have shown high performance levels in individual and cultural learning. Early Homo species demonstrated high individual learning levels when they innovated complex stone tools, bone tools and shell beads. It is believed that Homo sapiens first developed high individual learning levels before a high cultural leaning level became established.

Cultural Learning Mechanisms
In order to fully grasp the idea of culture, it is imperative to distinguish between the types of cognitive learning abilities that evolved from our Paleolithic ancestors which enabled individuals to successfully acquire ideas, beliefs and practices from their social environments. In certain cases, extracting information through individual learning can be rather costly. In this situation, natural selection will favour the development of cultural learning mechanisms, which will aid learners in efficiently acquiring adaptive information from other members of society at a lower cost. These mechanisms are categorized into two different forms of biased transmissions, which occur when some cultural variants are favored over others during the process of cultural transmission. They are labeled: content biases and context biases.

Content Biases
Content biases “cause us to more readily acquire certain beliefs, ideas or behaviours because some aspect of their content makes them more appealing”. An example of this is food preferences. When choosing between three different seasonings: sugar, salt, and chalk, content biases cause us to choose the sugar or salt due to evolutionary reasons. Salty or sweet flavours would act as indicators to ancient humans of food containing scarce nutrients and high calories. Natural selection has now favoured a bias to obtain a taste for salty and sweet foods so that we would be more inclined to consume them, demonstrating that human food preferences are influenced by content biases.

Additionally, after acquiring an idea, belief, value, or mental model through cultural transmission, an individual may be more likely to gain other ideas due to the fact that the two are related in a cognitive or psychological way. For example, if a society believes that a certain ritual will help enhance crop harvest, an idea might develop that a similar ritual will increase the chance of a woman conceiving, or successfully giving birth.

Content biases can be influenced by genetics or determined by fitness-enhancing cultural traits. For instance, food choice may result from a genetic preference for sugary or salty foods, as well as socially learned eating practices. Content biases are sometimes referred to as "direct biases".

Context Biases
Context biases result in our acquiring information from models (individuals observed and being learned from). Information is costly to acquire if one is learning individually, and it is more beneficial to extract information from those in society who are successful, skilled and well respected. There are two categories of context biases in cultural learning: model based biases and frequency-dependent biases.

Model-Based Biases

It is important for the learner to be selective when choosing their model, which can be done by relying on a range of cues related to skill, success, and prestige from the model. In this way, the learner can determine who possesses the most useful ideas, beliefs, strategies, and adaptive skills. When noting someone’s skills, the learner must directly observe and judge the model’s technique or performance. With regards to cues for success, indirect assessment occurs. For example, some cues might include the size of one’s house, the number of family members, amount of animals killed in a hunt, size of their crops, or anything else that is related to skill. As this cultural learning mechanism becomes more widely used, there will be a high demand for skilled and successful individuals. In order for learners to gain access to these rare skilled models that will help them in information gathering, they will begin to show deference. This will include assisting with difficult labour, publicly praising the individuals they are learning from, caring for their offspring, and offering them gifts. Other members of society will notice the deference and how people are acting towards this model, which demonstrates the model’s prestige. If many individuals are showing deference towards this model, the learner can determine that this is someone who they should pay attention to for cultural learning. Using all three of these assessments: skill, success, and prestige, the learner can then get a decent estimate of whom to learn from.

Evidence for Selective Model-Based Cultural Learning

Henrich states that there are six main points in providing evidence for success and prestige biased cultural learning:


 * 1) Imitative patterns spontaneously appear in incentivized and non-incentivized circumstances, in both non-social and social situations, including situations that involve direct competition among the learners.
 * 2) The effects repeatedly emerge across a broad range of contexts, including economic decisions, opinions, food preferences and consumption, beliefs, and dialects.
 * 3) Consistent with theory, the amount of cultural learning observed depends critically on the degree of uncertainty found in the environment. As uncertainty increases, so does cultural learning.
 * 4) These learning patterns emerge even when the model's domain of competence, success or prestige is apparently unrelated to the behavioural domain in question.
 * 5) Diverse findings from laboratory experiments in both economics and psychology, using very different experimental paradigms, consistently converge, giving us confidence in the findings' robustness across experimental contexts.
 * 6) The patterns of cultural learning observed in the laboratories fit closely with field data, giving us confidence that the effects observed in the artificial context of experiments actually matter in the real world.

An experiment done by Offerman and Sonnemans found out that not only do people copy economic choices and investment strategies, but that they also imitate beliefs from successful people. Psychological experiments have demonstrated that individuals acquire opinions from prestigious sources, especially in uncertain or difficult situations. A study done by Wasserman showed that the act of committing suicide and the methods used for such act are imitated according to prestige and self­-similarity. For instance, studies in the US and Japan showed that suicide rates significantly rose after a celebrity had committed suicide. In the Diffusion of Innovations by Rogers (1995), there is a chapter that explains how the diffusion of new ideas, technologies, and practices is influenced by social leaders (those with a high social status, that are well respected and widely connected, and that serve as effective social models for others).

Conformist Bias

An issue arises when an observable difference in skill, success and prestige among individuals do not match up with the observable differences in behavior, beliefs and practices. If there is an individual who uses different strategies from the rest of society, yet still appears to be successful, the learner needs to chose wisely whom to gather information from. One way to choose is to copy the methods of the majority. In this manner, the individual can obtain valuable information from the behaviors of many others. However, if all the individuals used this method, there would be no cultural evolution. What drives cultural evolution is a combination of different models of social and individual learning.

Henrich states that the combination of conformity bias with individual learning and vertical transmission leads to three predictions:


 * 1) Individuals will prefer conformist transmission over vertical transmission, assuming it is possible to access a range of cultural models at a low cost, which is often the case.
 * 2) As the accuracy of information acquired through individual learning decreases, reliance on conformist transmission over individual learning will increase.
 * 3) Individuals should be sensitive to substantial shifts in the relevant environments so that they decrease their reliance on conformist transmission after recent fluctuations, or increase it after immigrating.

Human Adaptability via Cultural Mechanisms
Humans inhabit a wide range of environments that demand a large number of adaptations. The diverse and complex behavioural repertoire that contributes to increased fitness biology in humans is not solely the result of genetic evolution, but also of cultural learning processes. The acquisition of culture relies on the accumulation of adaptive knowledge as well as the interaction among individuals. Human behaviors are favoured on the basis of their cultural fitness, which needs not be directly correlated with genetic fitness, or reproductive success.

Cultural learning is a type of social learning that leads to adaptability over a wide intermediate range of environmental fluctuation, and is initiated through individual learning. Environments fluctuate over tens, hundreds, or even thousands of generations. At the low extreme, there is not sufficient accumulation of adaptive knowledge to generate cultural learning. At the high extreme, adaptability can possibly be accomplished through genetic evolution at a lower cost. However, throughout a wide intermediate range of environmental fluctuation, cultural learning is favoured since it operates upon a large repertoire of accumulated knowledge, leading to adaptive capabilities faster than genetic evolution. Cultural learning leads to increased fitness by allowing the acquisition of behaviours that individuals cannot acquire on their own during their lifetime, and by indirectly decreasing the cost of individual learning. A simple model demonstrates that if social learning does not decrease the cost of individual learning, then social learning will not lead to increased fitness. In this model, the fitness of individual learners remains constant independent of the frequency of social learners. On the other hand, the fitness of social learners decreases as their frequency increases. When there are only a few social learners relative to individual learners in a population, their fitness is higher than that of individual learners. Most of these social learners are likely performing the correct behaviour without paying for the high cost of individual learning that individual learners must pay. As the frequency of social learners increases, their fitness decreases since there are now relatively less individual learners that can transmit the correct behaviour, making it less likely for social learners to be performing it. Ultimately, natural selection drives the population to equilibrium, at which point the frequency of social learners has increased to the extent that their fitness has decreased enough to become equal to that of individual learners. At equilibrium, individual learners and social learners do equally well. Individual learners are always performing the correct behavior at a high cost. Social learners always acquire the behavior at a lower cost than individual learners, but since the behavior of social learners contains more mistakes at equilibrium than before the population reached equilibrium, it is the increase in the inaccuracy of the behavior performed by social learners that increases their cost, making their fitness equal to that of individual learners. Moreover, the mean fitness of a population at equilibrium is equivalent to its mean fitness when there are only individual learners. When the frequency of social learners surpasses the equilibrium point, the fitness of social learners falls below that of individual learners, and the mean fitness of the population decreases. In other words, an individual learner entering a population of solely social learners always has a higher fitness than the others. In this model, a population of individual learners that is exposed to social learners equilibrates at a fitness value equal to that of the starting population of only individual learners. Therefore, social learning does not lead to increased fitness at equilibrium when it does not decrease the cost of individual learning.

However, another model suggests that if social learning leads to a reduced cost in individual learning, then social learning will lead to increased fitness, and thus adaptability. In this model, the fitness of individual learners increases as the frequency of social learners increases, while the fitness of social learners decreases as their frequency increases. As a result, the population reaches equilibrium sooner than in the previous model, and the mean fitness of the population at equilibrium now fixates at a higher fitness level. It is this type of social learning that is referred to as cultural learning.

Essentially, cultural learning leads to increased fitness in a population by allowing the acquisition of complex behaviors that individuals cannot discover on their own during their lifetime. This mechanism does not only lead to adaptability directly, but also indirectly, by decreasing the cost of individual learning. Individual learning alone leads to sub-optimal behaviours. Once these sub-optimal behaviors exist in a population, cultural learning can start to take place. As the frequency of cultural learning increases in a population, it approaches a threshold value after which it becomes stable. When cultural learning is stable, new individual learners can rely upon the widely spread repertoire of behaviors and build newly complex behaviors. Therefore, cultural learning enhances individual learning. This validates the aforementioned model, where the fitness of individual learners increases as the frequency of cultural learning increases.

As the learning cycle continues, cultural learning ultimately drives the population to an optimal fitness level. Natural selection favors cultural learning when its cost is less than the benefit obtained from the accumulation of newly acquired behaviors. Cultural learning is unstable at first in a population, but as it becomes more common, the likelihood that it reaches the threshold value increases, and thus the more likely it becomes that reliance on cultural learning is established. After reliance on cultural learning is reached, it is maintained by natural selection, since common cultural learning enhances the rate of accumulation of adaptive behavior to the extent that this benefit becomes larger than the cost of cultural learning mechanisms. In the long run, cultural learning allows access to a behavioral repertoire that has been established over generations, leading to adaptability. It is hypothesized that humans surpassed the cultural learning threshold that allowed for reliance on cultural learning through cultural drift, a process that can be interpreted as analogous to genetic drift.

Adaptive Behaviours in Humans
Humans have acquired a wide range of adaptive behaviours through individual and cultural learning cycles over several generations. These behaviours differ from those of other species in their complexity, and are largely responsible for the evolution of the human species.

Evolution of Food Foraging
Food foraging is an adaptive strategy which involves a mixture of fishing, hunting and gathering wild foods. Today, less than 0.005 percent of the world's human population of over 6.8 billion uses foraging as a main means of subsistence. These populations live in societies that are located in marginal locations such as the frozen Arctic tundra. As a result of foraging societies disappearing from areas that have naturally high abundances of food and resources, anthropologists are cautious when making connections between present food foraging groups and ancient human foragers.

Usually, foraging groups are able to have an abundance of food and achieve balanced diets. Foragers are at less of likelihood to suffer from severe famines when compared with farmers. While some contemporary food forager's diets may obtain up to 70 percent of plant foods, groups living in the Arctic tend to have lower proportions of plant foods than meats due to the lower availability of plants for most of the year.

Foraging groups have plenty of leisure time allowing them to focus on family ties, social life and spiritual development at a higher degree than those living in farming or industrial societies. Present-day foraging societies do not adhere to the ancient ways of attaining foods because they are ignorant of other adaptive strategies. Rather, foraging is the best means of survival for the situations that these groups are in.

Studies have been done on mice to demonstrate how the cultural transmissions of foraging information’s may work. The foraging efficiency of Norway rats were seen to increase in observer rats when they had previously watched a trained demonstrator rat unearth buried carrots. This increase in foraging efficiency was not seen in observer rats who watched untrained rats. The study also showed that chains of transmission were established when observer rats who learned how to find food were used as demonstrator rats for the subsequent naive observer rats. The results indicated that through cultural learning, transmissions of mechanisms in food foraging may result in the spreading of a pattern of behaviour through populations.

Evolution of Horticulture and Pastoralism
Around 10,000 years ago in Southwest Asia in an area known as the Fertile Crescent, the transition from food foraging to food production first occurred. Humans became more dependent on domesticated crops as a food source and mostly gave up their nomadic way of life. With more sedentary lifestyle conditions, they were able to build more permanent homes. The domestication of plants and animals was a momentous achievement which transformed their cultural systems. As a result, humans developed new ideological patterns, economic arrangements and social structures.

From plant domestication, societies embraced horticulture, where small gardening communities would use simple hand tools to grow crops without use of irrigation nor plows. Horticulturalists will often grow enough food for the communities’ subsistence but will also produce modest surpluses for inter-village feasts and exchanges. Although horticulturalists main supply of food is produced from their gardens, they will also forage foods when in need or when possible. The role of cultivating plants in the evolution of societies went beyond food, fiber and medicine. All aspects of human culture reflect the significant meanings of plants due to its vital influence on the development of civilization.

Pastoralism is another striking example of human adaptation to the environment. It is the breeding and managing of herds of domesticated herbivores like goats, sheep, cattle horses, llamas or camels. It is different from animal husbandry in that it focuses on breeding and herding the animals. Pastoralists depend on their livestock for daily survival and the food and drink of their grazing animals determine the pastoralist’s everyday routines. Pastoralists do not generally establish a sedentary lifestyle since they must move with their large herds to new pastures frequently.

The Neolithic Revolution: An Evolutionary Perspective
The Neolithic revolution occurred in 6000-3000 B.C.E. As a result of domesticating crops, humans settled down to till the soil, sow, weed protect, harvest and safely store their crops. Permanent dwellings were established and they started to make pottery for storage of food and water. It is thought that the Neolithic revolution was forced upon the food foragers as a result of climate changes.

Changes in the subsistence strategies have been important in many of the major evolutionary changes in human evolution. It has been associated with the increase in population densities, increase in social inequality between genders and divergences in social structure. By looking at Neolithic cemetery data, previously unknown information about demographic processes related to the transition from food foraging to an agricultural economy has been uncovered. Less than a millennium after the transition to agriculture, dramatic increases in birth rate and as a result, population growth rate occurred. This process has been named the Neolithic Demographic Transition and has been detected in Europe, North America, Mesoamerica and South America. From the increased populations’ emergences of some social practices occurred.

Food foragers lived with low fertility and no heritable wealth of consequence. Their societal systems were primarily egalitarian. However with the transition to domestication of animals and plants, societies began to be shaped by important resources (gardens, livestock, fishing territories, etc.) that were owned or controlled and could be inherited by future generations. As a result, access to resources influenced the success of future generations which generated inequalities in political powers and wealth.

There is evidence that suggests that the effects of the Neolithic revolution still impacts on things like incomes across the world presently. The differences in the transition times from food foraging to agriculture in human societies may lead to differences in technological developments and social organizations.