During the seventies, evolutionary
theorists started arguing that human behavior is amendable to the same
Darwinian treatment as all (other) biological features. Consequently, culture
has no longer been the proprietary domain of social scientists, but has been
investigated by anthropologists, evolutionary biologists, and psychologists in
various ways, resulting in evolutionary accounts of a wide variety of human
characteristics, such as sexual behavior, mate choice, marital systems,
homicide, infanticide, religion and so forth. When the dust raised by the sociobiologists
in the seventies had settled, four approaches to an evolutionary study of human
mind, behavior, and culture emerged.

Human behavioral ecologists use evolutionary
reasoning to understand our contemporary behavior on the premise that human
behavioral strategies are adaptive across a wide range of ecological and
cultural conditions. How, they ask, is the behavior of individuals influenced
by the ecological and cultural environments in which they live, and how do the
alternative behavioral strategies these individuals adopt to cope with
environmental challenges give rise to cultural differences?

Evolutionary psychologists are only indirectly
concerned with current adaptive behavior. Rather, they use evolutionary
thinking to generate hypotheses about the adaptive problems that the human
mind/brain had to solve in the selective environment of our ancestors (during,
say, the Pleistocene), and in the evolved structures or mechanisms that are
responsible for current behavior (be it adaptive or not).

Memeticists — the meme being the
analogue to the gene as the biological unit of inheritance — hold that
cultural evolution can be modeled by the same basic evolutionary principles of variation
and descent with modification as can biological evolution. Different
memes, they claim, that is pieces of cultural information, can be transmitted
from one individual to another in a process of cultural selection with
different rates of success. Those memes that are transmitted are thereby replicated
in the same sense genes are replicated in the process of natural selection,
giving rise to a Darwinian process of descent with modification in the realm of
culture.

Finally, there is the dual-inheritance
theory (sometimes also called ‘gene-culture coevolution‘) of,
amongst others, the anthropologists Robert Boyd (Professor of Anthropology at
the University of California at Davis ) and Peter Richerson (Professor of
Environmental Science and Policy at the University of California at Davis).
They agree with the other approaches just mentioned that culture should,
repeated allegations of social scientists to the contrary notwithstanding, be
modeled as a Darwinian evolutionary process. However, they also discard the
attempts of evolutionary psychologists or human behavioral ecologists to base a
study of cultural evolution solely on innate, genetically encoded information.
They argue, just like memeticists, that transmitted cultural information is too
important a factor to be simply ignored — one of the most striking facts about
the human species is that there are important and persistent differences
between human groups that are created by culturally transmitted ideas, and not
by genetic, physical, or biological differences.

What sets them apart from memeticists,
though, is their conviction that there is no analogy between cultural evolution
and biological evolution, between memes and genes that can ground a process of
cultural evolution strictly analogous to biological evolution. Cultural and
biological evolution may be similar in that important information is
transmitted between individuals and both create patterns of heritable
variation. The differences, however, are much more salient. For instance,
culture is not based on direct replication but upon teaching, imitation, and
other forms of social learning, the transmission of culture is temporally
extended and not restricted to parents and their offspring, cultural evolution
is not necessarily particulate, and cultural variation is not necessarily
random.

Culture, according to Boyd and Richerson,
is part of human biology, but accounts concerned solely with genetic
factors are inadequate because they ignore the fact that culture itself can and
does shape the adaptive environment in which biological evolution takes place
— culture constrains genetic evolution by creating durable changes in human
behavior, so that human genes necessarily evolve in a culturally constructed
environment. Conversely, accounts aimed solely at explaining cultural
replication are inadequate because they ignore the fact that genes and
processes of biological evolution affect cultural evolution, for instance for
instance by forming psychological predispositions that bias what people
imitate, teach, or are able to learn. Hence, an evolutionary account of culture
must acknowledge that genes and culture coevolve. This is the central
tenet of dual-inheritance theory, which tries to investigate the circumstances
under which the cultural habits adopted by individuals are influenced by their genes,
and how, in turn, the natural selection pressures of a population the guide
biological evolution may be generated by culture.

Boyd and Richerson initially presented
their account in 1985 in their book Culture and the Evolutionary Process
(Chicago: The University of Chicago Press). In ‘The Origin and Evolution of
Cultures‘, they have
now collected twenty papers written in the period 1987 — 2003. These papers
are divided into five sections, each of which begins with a short but
informative introduction by Boyd and Richerson.

Part one is entitled ‘The evolution of
social learning’ and addresses the question how our capacity for culture — our
capacity to transmit information by teaching, imitation, and other forms of
social learning, which enables us to acquire skills, beliefs and values from
the people around us — has evolved. Does a capacity for social learning
increase the fitness of individuals or groups of individuals, and if it does,
why does it do so? Under which conditions do selective processes favor
individuals able to adopt behavior from others (chapters 1, 2, and 3)? And if,
as seems plausible, our capacity for cumulative cultural transmission sets us
apart from all other animals and has boosted our fitness compared with the
fitness of creatures restricted to individual learning or simple forms of
imitation, why has it appeared only so recently in evolutionary history, and
why has it not evolved independently in a number of other species as well
(chapters 4 and 5)?

Part two, entitled ‘Ethnic groups and
markers,’ is the shortest. Boyd and Richerson develop two models designed to
explain under which conditions evolution favors mechanisms of cultural
evolution that result in ethnic or social grouping. What are the processes that
would cause human populations to split into two groups distinguished by
cultural marker traits, and could these processes give rise to cultural
variation that is biologically adaptive, i.e. that increases the reproductive
success of the group members (chapters 6 and 7)?

Part three is entitled ‘Human
cooperation, reciprocity, and group selection,’ and is by far the longest.
Apart from the general idea of gene-culture coevolution, Boyd and Richerson are
best known for the work described in the seven papers in this part (chapters 8,
9, 10, 11, 12, 13, and 14). There, they are concerned to show that it is very
unlikely that large-scale cooperation among humans can be accounted for solely
by the classical idea of reciprocity. Currently, there is a widely held
consensus that group selection — selective processes in which groups,
as opposed to individuals or genes are the beneficiaries — is a highly
unlikely hypothesis that can occur only under very restricted circumstances.
However, Boyd and Richerson propose an account that views cooperative behavior
as the evolutionary result of a process of group selection, not at the level of
biological evolution, but at the level of cultural evolution. The basic idea is
that theoretical models can be constructed that show that virtually all circumstances
that favour social learning also tend to lead to strong within-group
conformity, which then, in turn, enables us to understand the evolution of
cooperation among humans.

Part four, ‘Archaeology and culture
history,’ contains three relatively long papers in which Boyd and Richerson try
to show how an evolutionary theory of cumulative cultural evolution, in
particular their own account, can be of interest and of use also for those
interested primarily in history and/or archaeology (chapters 15, 16, and 17).

Part five is, as its title ‘Links to
other disciplines’ suggests, the most heterogeneous and contains primarily
meta-theoretical or methodological considerations. Boyd and Richerson develop
their theory of cultural evolution as a complement of rational choice theory in
economics (chapter 18), defend the use of simple mathematical models in giving
evolutionary accounts of culture and cultural transmission (chapter 19), and try to show why memetics
is inadequate as an approach to the study of human cultural evolution (chapter
20).

As is common among dual-inheritance
theorists, Boyd and Richerson rely heavily on mathematical models (similar to
those used in population genetics) that take into account specific, but
simplifying, hypotheses about human psychology and the nature of human social
learning in order to make intelligible how cultural variants can spread in
populations, how the adoption of the beliefs, skills, habits and values of
others can yield an evolutionary pay-off in terms of an increased fitness, and
how and why populations of individuals with a capacity for culture can do, as a
whole, better than populations of individuals without such a capacity. This is,
as brief as possible, what ‘Culture and the Evolutionary Process‘ is
about.

There is much to learn from the work of
Boyd and Richerson, and the initiative to bring together some of their
scattered papers in this volume is laudable. Many professional anthrologists,
biologists, philosophers and psychologists interested in the study of culture
and the evolution of mind and behavior will benefit from it — modulo the
slight reservations discussed soon. Is there anything critical to say?

Let me briefly note one quite general
point I know many find disappointing about the theoretical approach of
dual-inheritance theorists. One of the good things about the alternative
approach of evolutionary psychology is that it generates testable hypotheses.
This prevents it (if the tests are designed carefully and unbiased) from
drifting into mere evolutionary story-telling. If Boyd and Richerson, too,
would use their models to generate such testable hypotheses (as they do, for
instance, quite nicely in chapters 6 and 7 on the evolution of ethnic markers),
this would prevent them from creating the impression of drifting into mere
‘model-constructing’. That use of models brings me to a final misgiving I have
about ‘Culture and the Evolutionary Process.’

Is Boyd and Richerson’s book a must-have
for anyone interested in evolutionary accounts of culture? Unfortunately, I
think, the answer is ‘No, not for anyone.’ Following the complicated
mathematical equations that underlie many of Boyd and Richersons models is
tedious, if not outright impossible, for all but the most gifted mathematicians
among ordinary anthropologists, biologists, philosophers, psychologists and
educated laymen. Boyd and Richerson do little to help those of us not familiar
with the subtle art of mathematical models out of their predicament. They do
attempt (in chapter 19), to show why the use of simple models is helpful in the
study of cultural evolution (which I do not question). However, their focus
there is on the question whether simple models are not too simple to
yield trustworthy results, while even those ‘simple’ models will exceed the
mathematical skills of the average reader (see, for instance, those contained
in chapters 1, 2, 3, 8, 9, 10 or 18). This is unfortunate, because what Boyd
and Richerson have to say about cultural evolution and the interaction of
genetic and cultural factors is not only interesting, but most of it seems
absolutely right and would certainly deserve a wider audience. It might be
that, as Boyd and Richerson claim, all serious students of human behavior ought
to know enough math to at least appreciate the contributions of simple
mathematical models to the understanding of cultural evolution, but ‘ought’
famously does not imply ‘is’, and as long as most of us do not know
enough math, it would be a great thing if we could nevertheless participate in
the interesting and groundbreaking research conducted by Boyd and Richerson.

Fortunately, by the way, we can. Not in The
Origin and Evolution of Cultures, but in their jointly authored book Not
by Genes Alone: How Culture Transformed Human Evolution (Chicago: The University
of Chicago Press 2005)(reviewed in Metapsychology 9:47), which indeed I recommend as a must-have for anyone
who takes a serious interest in the evolution of culture, mind and behavior.

 

© 2006 Sven Walter

 

Sven Walter, Ph.D., Department of
Philosophy, University of Bielefeld, Germany

Categories: Genetics, General