Chapter Review

Human beings, like all other organisms, are a product of biological development and environmental interactions. Behavior itself is a phenotypic trait and, as such, reflects a history of specific interactions between genes, experience, and environment. It is important to keep in mind that biology may provide a proclivity toward a particular characteristic (for example, tall/short, good vision/myopia), but this will not necessarily develop without the proper environmental interactions. In this sense, environment and genes are both biological in nature.

The field of evolutionary psychology has attempted to address the question of human brain evolution and behavior from an evolutionary perspective. The basis of inference for evolutionary psychologists is the environment of evolutionary adaptedness (EEA), or the past situations that human cognitive abilities were designed to address. One problem with this notion is that little is known about the genetic basis of psychological concepts. Whether certain characters evolved early in evolution or much later is highly variable and often unknown, and lack of this information leads to uncertainty concerning the particular environment of adaptation. After all, human evolution proceeded through a great many ecological and cultural changes over the past 2 million years or so. Furthermore, even if psychological variables were simultaneously fixed at a given point in human history, determination of the characteristics of the environment would remain a highly speculative venture. It is unclear if the model of a foraging society in the present adequately represents the past social and ecological environments.

Theoretical problems are difficult for practitioners of evolutionary psychology to explain away. Yet the field itself has led to some provocative insights. Biases in human cognitive processes are evident in problem-solving tasks that involve social exchange—that is, problems for which there is a potential gain or loss in social status. Also, memory appears especially sharp in keeping track of debtors while accidentally forgetting debts to others. Human beings appear to be especially proficient at playing the game of social manipulation and status acquisition and are, in that respect, much like our nonhuman primate relatives.

Human culture has long been recognized as a highly specialized means of adapting to a rapidly changing environment. However, humans are not unique in having a means of adaptation that is transferred from generation to generation through nonbiological means. Information transmission may occur via the mechanisms of social facilitation, observational learning, and imitation. Indeed, cultural variations in diet and behavior have been observed among regional populations of the common chimpanzee. When human adaptive behaviors are examined in light of the primatology literature, the differences between human and nonhuman primate behaviors appear to be differences in degree, not differences in kind.

Furthermore, there are compelling arguments that humans share a tendency to avoid incest with the rest of the primate order. Most humans do not mate with close relatives, and such unions, whether carried out in the open or in secret, are reviled. Humans also rarely mate with nonrelated individuals they grew up with. Ethnographic examples such as the Israeli kibbutzim (collectively organized communities where all children are raised together in large groups) and Taiwanese minor marriage (infants are betrothed to each other and raised together in the "husband's" household), in which people who grow up together rarely form lasting, sexual relationships, substantiate the idea that people avoid undesired matings in patterned ways.

The necessity of successful cultural transmission is imperative among humans. In this way, culture is a key adaptation and a derived trait of our species. Observational learning and imitation has been selected over many generations for the adaptive advantages they confer on their practitioners. This bent toward observational learning—and a relatively elongated learning period—are specific adaptations to specific environments.

The acquisition of language remains one of the most pivotal adaptations in the course of human evolution. Language allows people to communicate, to interact with each other's thoughts (if expressed), and to bridge dimensions of time and space. Language greatly expands our conscious awareness of the world. While there are hundreds of languages spoken among different peoples worldwide, numerous characteristics are shared among all humans in their capacities for spoken language. The fact that there are commonalities in language acquisition and use among humans suggests that human language is a highly evolved system of communication, formed by natural selection. Unlike other learned capacities, language does not require teaching, yet it involves intricate coordination of vocal cords, lips, tongue, mouth, and various brain regions, simultaneously.

Furthermore, the structure of language provides for nearly infinite combinations that express different ideas in different ways. Phonemes, the most basic unit of perceivable speech, are combined using grammar and syntax to produce novel expressions. The development of language capacities likely resulted from an evolutionary advantage conferred on language practitioners in the past, from the most rudimentary forms of symbolic communication to other intermediate forms. Modern great apes are capable of learning symbolic communication systems, suggesting there are some commonalities in cognition. Whether apes use a language system in the wild has not yet been demonstrated, although it has also not been disproved.