Despite the backlash against evolutionary approaches to human behaviour sparked by sociobiological theory, evolutionary theory seems to be gaining new influence in psychology, being described as a 'new science of the mind' (Buss, 1999). More specifically, evolutionary developmental psych- ology has been described as an emerging interdisciplinary field, its goals
being 'to identify the genetic and ecological mechanisms that shape the development of ... phenotypes and ensure their adaptation to local condi- tions' (Geary and Bjorklund, 2000: 57). The interplay between genetic and ecological conditions to determine the phenotype (physical and behaviour- al characteristics) is known as epigenetics (imprinting, as described by ethologists, is a good example of epigenetics). Like sociobiology, evidence is drawn from other animal (especially primate) species, from fossil records of ancestors of Homo sapiens and from a consideration of modern hunter- gatherer societies.
In a manner reminiscent of Havighurst's notion of developmental tasks (see Chapter 3), evolutionary developmental psychologists divide the life- span into a number of stages defined by differences in physical develop- ment, social dependence and social goals — for example, infancy, childhood, juvenility, adolescence and adulthood (Bogin, 1997, cited in Geary and Bjorklund, 2000). An important function of the extended pre- adult period of development in humans is said to be to provide the oppor- tunity for practice of skills needed for survival and reproduction (for example, competition for mates), through play, social interactions and exploration of the environment. It has also been argued that social and cognitive immaturity may themselves serve adaptive functions that are con- cerned with the shorter-term survival of the young individual rather than being a preparation for adulthood. For example, children's short auditory memory span might aid comprehension of language by reducing the amount of information to be processed (Geary and Bjorklund, 2000).
In infancy and childhood, attachment to parents is seen as the central social relationship, functioning to keep the young organism alive by keep- ing it close to parents and increasing the level of parental investment in their offspring (see Chapter 5). Readers are also referred to Susan Goldberg's (2000) book (Attachment and Development) in this series for a rich discussion of this issue. The fact that there are individual differences in quality of attachment, as shown by the studies of Ainsworth (e.g.
Ainsworth andWittig, 1969) is taken as evidence that attachment is an epi- genetic process, with the contribution of genes and environment yet to be studied.
As children grow older, the shift away from parents towards peers, espe- cially same-sex peers, is seen as preparatory for adult reproductive activ- ities. For example, boys' social relationships are concerned with status and dominance, which can be interpreted as being preparatory for competition for mates in pre-industrial societies, while girls' more intimate relationships with each other can be seen as fostering a supportive network for later parenting activities (Geary and Bjorklund, 2000). It is of interest that this traditional sex-typed interpretation (competing males but cooperating females) has required modification in the light of recent research (e.g.
Crick and Bigbee, 1998) which has broadened the definition of aggression
from physical and verbal types to social forms more typical of girls, such as spreading rumours about others and keeping them out of friendship groups. Thus Geary and Bjorklund acknowledge that girls also compete with one another, proposing that perhaps upsetting the social networks of competitors lays the groundwork for later competition for mates. In fact, our own research does show that competition between teenage girls over boyfriends is one (of several) triggers for social aggression (Owens et al., 2000).
The evolutionary framework has been applied to cognition as well as to social development. It has been proposed that there are hierarchically organized modules of the mind that have evolved to process both social and non-social (ecological) aspects of the world (see Table 2.1) (Geary, 1998, cited in Geary and Bjorklund, 2000). This theory is an exemplar of Pepper's (1942) formism metaphor, in that it is based upon dividing the world into categories. Modules related to the social world are divided into those concerning different social groups and those that are individually based, such as theory of mind. Ecological modules are divided into the biological and the physical. While the basic neural structures underlying these modules are seen as inherent, they develop as children initiate activ- ities and gain competence in 'folk psychology, folk biology and intuitive physics' (Geary and Bjorklund, 2000: 62). In other words, epigenetic processes are responsible for phenotype, although the mechanisms involved are poorly understood. The notion of the sensitive period is incor- porated, with the additional suggestion that sensitive periods may be relat- ed to the position of modules/submodules in the hierarchy, with the sensitive period being shorter and earlier for lower-level than higher-level modules.
Table 2.1 Evolutionary developmental theory: evolved domains of mind Domain of
information:
Examples of information- processing modules:
social biological physical
Subdomain:
Function of information- processing modules:
individual online monitoring of dyadic interactions;
maintaining interpersonal relationships
group parsing social universe into kin, friends and competitors
categorizing and representing behaviour/
growth patterns of flora and fauna, e.g.
food sources
guiding/
representing movement in three- dimensional space; using physical materials language
theory of mind
ingroup outgroup
flora fauna
movement representation
Source: based on information in Geary and Bjorklund, 2000
A goal of evolutionary developmental psychology is to understand how biases and constraints on behaviour determined by evolutionary pressures are relevant for the modern world (Geary and Bjorklund, 2000). For example, while children the world over are biologically predisposed to learn language, reading is a cultural expression of language (Snowling, 2000) and thus inherently more difficult to learn. Similarly, Geary and Bjorklund suggest that while deadly male-on-male violence is an under- standable result of evolutionary pressures to compete, this could be chan- nelled more safely into alternative competitive activities, such as athletics (a view, incidentally, that would be strongly challenged by some sociolo- gists concerned with gendered aspects of education, who would see this as encouraging harmful 'macho' attitudes (Gilbert and Gilbert, 1998).
While many theories of development focus on specific aspects, the above overview makes clear the breadth of coverage afforded by evolutionary developmental theory: 'an evolutionary perspective should provide a useful framework for conceptualizing and guiding future research across many of the developmental specialties (e.g. social, cognitive, and neuroscientific)' (Geary and Bjorklund, 2000: 63). This implies that evolutionary theory could play an important role in integrating otherwise diverse theories, a possibility raised previously by Hinde (1992a; 1992b) and discussed further in Chapter 11 of this book.
The evolutionary perspective on human development carries some dan- gers, however, some of which we have alluded to already. Hinde (1992b) warned against drawing simplistic and anthropomorphic parallels between animal and human behaviour. He provided the example of the removal of an infant from its mother in both humans and rhesus monkeys. While in both cases the greater the disruption to the mother-infant relationship, the more the infant's behaviour is disturbed, the dynamics differ in the two cases. Human children are more disturbed by spending the separation in a strange environment, while monkey infants are more disturbed by remain- ing in the familiar group environment (because of the effect of removal from the group on the mother's social relationships on her return). Thus, rather than simply drawing parallels, animal data should be used to suggest principles that can then be tested in the human case. More recently, and in a similar vein, Archer (2001) has argued that the value of evolutionary psychology lies in suggesting novel hypotheses that can be tested. However, Segal (2001) suggests that evolutionary-based tales of wicked step-parents (with their lack of genetic investment in their step-children), competitive men and nurturing women are simply cliches repackaged as new insights.
Other opponents of the evolutionary approach maintain that, while our evolutionary history clearly empowers and limits our behaviour, this is at such a level of generality as to be unhelpful in considering most specific human behaviours (Rose and Rose, 2001). Readers interested in pursuing this debate in more detail are referred to Archer's (2001) article and the
supportive and opposing papers that follow it, and to a paper by Ketelaar and Ellis (2000), which addresses the question of whether evolutionary explanations are unfalsifiable; we discuss this further in Chapter 11.
Further information about evolutionary developmental psychology can be found in Bjorklund and Pellegrini (2002).