What today is called evolutionary psychology (EP) is an outgrowth of earlier movements
in sociobiology, ethology and behavioral ecology that applies the basic
principles of neo-Darwinian evolution to explain contemporary human behavior.
According to EP, the human mind has been prepared by natural selection,
operating over geological time, for life in a human group. As such, according
to Buss [1999], EP should be especially committed to answering four key
questions: (a) Why is the mind designed the way it is? (b) How is the mind
designed - what are its mechanisms? (c) What are the functions of these
mechanisms, and how are they organized? (d) How does environmental input
interact with these mechanisms to produce behavior? Within this framework,
evolutionary developmental psychology (EDP)
can be viewed as a more specific theoretical perspective that has been broadly
defined as 'the application of the basic principles of Darwinian evolution,
particularly natural selection, to explain contemporary human development. It
involves the study of the genetic and environmental mechanisms that underlie
the universal development of social and cognitive competencies and the evolved
epigenetic (gene-environment interactions) processes that adapt these
competencies to local conditions; it assumes that not only arc behaviors and
cognitions that characterize adults the product of selection pressures
operating over the course of evolution, but so are characteristics of
children's behaviors and minds' [Bjorklund and Pellegrini, 2002, p. 4]. From
this point of view, EDP can be considered simultaneously as (1) a general
psychobiological framework to understand development, (2) a source of
experimental hypotheses and questions about development and (3) a perspective
to produce and test interpretations about developmental
outcomes from a phylogenetic point of view.
The basic principles assumed by EDP
can be summarized as follows [Bjorklund and Pellegrini, 2000, 2002].
(a) The extended juvenile period of
H. sapiens was favored by the need (and the time necessary) to master an
increasingly complex social-technological environment. This extended youth had
implications for the evolution and development of the brain as well as for
psychological development.
(b) Evolution favors ontogenetic
diversity (variation), because humans live in a wide range of environments, and
this requires flexible cognitive and behavioral systems to survive.
(c) Concerning the effects of
natural selection on ontogeny, EDP holds that (1) many aspects of childhood
serve to prepare the way for adulthood and were selected over the course of
evolution - we refer to these as deferred adaptations; many sex differences in
social and cognitive abilities are good examples of deferred adaptations1; (2)
there have been different selection pressures on organisms at different times
in ontogeny, and some characteristics of infants and children were selected in
evolution to serve an adaptive function at that time in development and not to
prepare them for later adulthood - we refer to these as ontogenetic adaptations
[Oppenheim, 1981]; (3) there are aspects of childhood that did not evolve to
solve any recurring problem and have not been shaped by natural selection but
are a consequence of being associated with deferred or ontogenetic adaptations
(ontogenetic by-products) or are simply random effects attributed to mutations,
changes in the environment or aberrations of development (ontogenetic noise).
This could be the case, for example, of the belly button (by-product) and the
shape of one's belly button (noise), respectively [Buss et al., 1998].
(d) Many, but not all, evolved
psychological mechanisms are proposed to be domain specific in nature [Fodor,
1983].
Consistent with contemporary
thinking in much of cognitive science [Pinker, 1997], evolutionary
psychologists [Buss, 1995; Tooby and Cosmides, 1992] have emphasized that
humans (and other animals) evolved specific cognitive abilities to deal with
recurring problems faced by our ancestors (e.g., obtaining food, acquiring a
mate). Language abilities are often used as examples of domain-specific mechanisms.
From this perspective, humans did not evolve general, all-purpose
problem-solving faculties that can be applied across domains to any and all
circumstances. We concur with the significance of evolved domain-specific
abilities, but an EDP approach argues that domain-general mechanisms, such as
speed of processing and working memory, also underwent selective pressure over
the course of human evolution [Geary and Huffman, 2002]. This is consistent
with what we believe is the majority view among researchers in cognitive psychology, cognitive development and intelligence,
that human cognition is multifaceted, consisting of both relatively
domain-general and domain-specific abilities [Bjorklund, 2000; Fodor, 2000;
Sternberg, 1997].
(e) Behaviors, cognitions and
physical features that arise and change from infancy to old age emerge from an
interaction of evolved mechanisms and the environment. As such, developmental patterns are not conceived as
genetically predetermined (regardless of whether they are universal or not) but
as a result of an evolved epigenetic process that adapts human competencies to
local conditions, as described, for example, by the developmental
systems approach [Gottlieb, 2000; Oyama, 2000].
(f) Because the living conditions in
which our species evolved (the environment of evolutionary adaptedness) are far
different from the information age environments in which humans now live, many
of our species' evolved behavioral and cognitive adaptations are not well
suited to modern life and may actually be maladaptive.
As a whole, we see EP, and
particularly EDP, as an overarching theory or perspective that can and should
be applied to all realms of psychology and its
ontogeny. From our view, all accounts of human behavior should include the question
'Does this make sense from an evolutionary perspective?'
Developmental science (as other disciplines concerned with historical
processes) has traditionally assumed that knowing the past helps in
understanding the present and in predicting the future. This is no less true,
we argue, for phylogeny. Knowing the evolutionary history of a species can help
explain present and future behavior, including the amelioration of some
'problem' behaviors (e.g., child abuse, male-on-male violence, rape, reading/math
disabilities) [Bjorklund and Bering, 2002; Bjorklund and Pcllegrini, 2000;
Geary and Bjorklund, 2000]. We argue that EDP can be a useful tool to achieve
such purposes. However, at the same time, we propose that an EDP approach
should not be seen as replacing other theoretical perspectives that attempt to
account for the proximal causes of behavior. Rather, evolutionary developmental accounts should be seen as adjuncts to
other theoretical accounts (and vice versa) [Bjorklund, 1997].
EDP uses the extant knowledge of how
development and evolution proceed and integrates it into a single, hopefully
coherent, perspective. This perspective is based on a number of other
well-developed theories, both in ontogeny and in phylogeny, is subject to
falsification and to modification as new information/ideas are introduced and
can generate/test specific lower-level theories and hypotheses. In some cases,
we will surely oversimplify both development and evolution, and perhaps in
other cases make the processes more complicated than they actually are. But we
strongly believe that the application of evolutionary ideas to the study of
human development, with a critical evaluation of such research and theory, will
advance our science immeasurably and may serve as a common ground for developmental researchers studying disparate topics.
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