Gene-Culture Co-Evolution

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Gene-Culture Co-Evolution Kevin N. Laland
Centre for Social Learning and Cognitive
Evolution School of Biology University of St.
Andrews www.st-andrews.ac.uk/seal
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Hominin stone tools
(Figure fromFoley, 1995)
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Animal Traditions
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Recent positive selection in the human genome

• In the last 100,000 years humans have
• spread from East Africa around the globe,
• experienced an ice-age,
• undergone a transition from hunter-gatherer to
  agricultural societies,
• witnessed rapid increases in densities,
• new proximity of farmers to animal pathogens.

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Recent positive selection in the human genome

• In the last 100,000 years humans have
• spread from East Africa around the globe,
• experienced an ice-age,
• undergone a transition from hunter-gatherer to
  agricultural societies,
• witnessed rapid increases in densities,
• new proximity of farmers to animal pathogens.
• Recent statistical analyses of genetic data
  reveal hundreds of human genes that show signals
  of very strong and recent selection (e.g. in
  response to malaria, dairy farming etc).
• (Wang et al., 2006 Voight et al., 2006).

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Recent positive selection in the human genome
Homo sapiens have undoubtedly undergone strong
recent selection for many different phenotypes.
Given that most of these selective events likely
occurred in the last 10,000-40,000 yearsit is
tempting to speculate that gene-culture
interactions directly or indirectly shaped our
genomic architecture. (Wang et al., 2006,
PNAS p140).
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Pioneers of gene-culture co-evolution
Edward O. Wilson
Cavalli-Sforza Feldman Boyd Richerson
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Parallels between genetic and cultural processes
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Natural and cultural selection
Some cultural traits have a direct effect on
survival and natural selection may change their
frequency (e.g. smoking).
Other traits spread due to cultural selection
(e.g. blue jeans, frisbee).
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Vertical
Parents
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Vertical
Oblique
Parents
Teacher, Leader, Elder
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Vertical
Oblique
Parents
Horizontal
Friend
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Transmission biases
There may be biases in cultural transmission.
i) Direct bias given a choice between two or
more alternatives, genetic predisposition or
prior knowledge may favour certain types of
information being adopted. ii)
Frequency-dependent bias - the frequency of a
trait affects the probability of information
transmission, e.g. conformity.
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Dairy farming and lactose absorption
Human adults require the enzyme lactase to break
down the protein lactose that is present in cows
milk. Whether or not an adult can digest lactose
is largely down to whether he/she possesses the
appropriate copy of specific genes.
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Researchers have found that there is a strong
correlation between the incidence of the gene for
lactose absorption and a cultural history of
dairy farming. Milk products have
been a part of some human diets for 6000 years
Ulijaszek Strickland (1993)
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Feldman and Cavalli-Sforza (1989) modelled the
relationship between the spread of the gene for
lactose absorption and the spread of the cultural
trait. Their analysis supported the hypothesis
that the cultural practise of dairy farming
created the selection pressure favouring this
gene.
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A phylogenetic analysis of human societies by
Holden Mace (1997) supported the dairy farming
hypothesis and revealed that dairy farming
evolved prior to the spread of genes for lactose
absorption.
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Applications of gene-culture models
1. Inheritance of behavioural and personality
traits (Cavalli-Sforza and Feldman, 1973
Otto et al., 1995). 2. Adaptive advantages of
learning and culture (Rogers, 1988 Boyd and
Richerson, 1985 Feldman et al., 1996). -
cultural group selection (Boyd Richerson,
1985) 3. Application to specific cases -
evolution of language (Aoki Feldman, 1987,
1989) - excess female mortality and sex-ratio
evolution (Kumm et al., 1994) - sexual
selection (Laland, 1994) - evolution of
handedness (Laland et al., 1995) - the
emergence of incest taboos (Aoki Feldman,
1997) - cultural niche construction (Laland
et al., 2001) - evolution of prestige
(Henrich Gil-White, 2001)
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Evolutionary approaches to the study of human
behaviour
Historical approach
Contemporary approaches
Human Behavioural Ecology
Gene-Culture Co-evolution
Cultural evolution
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Fisherian Runaway Sexual Selection
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Trait (T2)
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0
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Preference (P2)
Kirkpatrick (1982)
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Unbiased Vertical Cultural Transmission
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Genetic
Trait (T2)
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Cultural
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Preference (P2)
Laland(1994)
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Biased Transmission favouring P2

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Trait (T2)


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Cultural
0
1
Preference (P2)
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Predictions and applications
There should be society-wide correlations
between culturally transmitted preferences and
gene-based traits (in both sexes)
The hypothesis could apply to many traits e.g.
skin colour, facial features, facial and body
hair, body shape, height, degree of character
symmetry, degree of neoteny, level of
aggressiveness, emotionality