The Imitation Factor by Lee Dugatkin, Free Press, $25, ISBN
0684864533
JUST when you thought it was safe to declare this the age of the gene, some
biologists beg to differ. The race to sequence the human genome grabs headlines,
and newspapers abound with claims that genes have been identified for
everything. Lee Dugatkin, a biologist at the University of Louisville in
Kentucky, is one who fears that such gene-centrism forms a blind spot when it
comes to other ways of transmitting information across generations.
Dugatkin accuses evolutionary biologists of ignoring the capacity of animals
to learn valuable skills and pick up useful information from others. He calls
this the 鈥渋mitation factor鈥�, and says that this phenomenon is both an
鈥渦nrecognised pervasive force of nature鈥� and 鈥渢he key to understanding the
complex relationship between genes and culture鈥�.
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His complaint is that theoretical models of sexual selection simply assume
that mate choice is determined solely by genes. The Imitation Factor draws on
Dugatkin鈥檚 studies of mate choice in the guppy, a small freshwater tropical
fish. The evidence he leans on most heavily to rebut such gene-centrism comes
from one experiment. In it, two male fish were secured at the ends of a standard
aquarium, one with a 鈥渄emonstrator鈥� female nearby. The 鈥渟ubject鈥� of the
experiment is another female guppy, placed in a container in the centre from
where she can see the first female interact with one of the males for several
minutes. Remove the demonstrator female, and allow the subject to choose between
the two males, and she consistently chooses the male that had the female nearby.
According to Dugatkin, she interprets the proximity of a female near to one of
the males as an indication that she has chosen the male as a mate, draws the
inference that this must be a high-quality male, and biases her own choice of
males accordingly. Further experiments ruled out alternative
explanations鈥攆or instance, that the female simply chose the side of the
tank with the largest number of fish.
On this basis, together with observations of similar phenomena in other
species, Dugatkin is ready to assert that the copying of mate choice is a simple
form of culture found 鈥渋n everything from bugs, fish, and birds to deer and
primates, including humans鈥�. But the true extent of mate choice copying is
contentious. As Dugatkin acknowledges, what looks like copying out in the field
has frequently been found to be something different. Careful experimentation has
revealed, for example, that female deer congregate round a particular male not
because they choose to mate with him but rather because they choose to be with
lots of females.
The sad truth for Dugatkin is that many of his colleagues do not believe that
copying has a major role in the mating decisions of guppies, either. One team
tried to replicate his result with guppies and reported failure. There is only
one species where there is incontrovertible evidence for mate choice copying:
the Japanese quail. But any reference to the elegant series of experiments by
Bennett Galef and David White is inexplicably missing from Dugatkin鈥檚 book.
The Imitation Factor is a work of advocacy. Dugatkin, it would seem, is
engaged in a crusade to rid the world of the curse of genetic determinism. If
biologists would only conduct studies like his guppy experiments, he says, they
would realise that the 鈥渃ultural鈥� influence is underestimated, and that genes
and culture interact subtly. Tragically, he tends merely to ask which effect is
bigger. This promotes a damaging 鈥渘ature versus nurture鈥� dichotomy. Oppositions
between genes and culture are miserably inadequate for capturing the multitude
of causal factors needed for any reasonable treatment of development or
evolution.
This book promised so much鈥攕ocial learning, imitation, memes,
gene-culture interactions, evolution. If only Dugatkin had reviewed the relevant
literatures more carefully, and consulted his colleagues for feedback, it might
have been a fascinating read.