Gene-Culture Co-Evolution Kevin N. Laland
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Transcript of Gene-Culture Co-Evolution Kevin N. Laland
Gene-Culture Co-Evolution
Kevin N. Laland
Centre for Social Learning and Cognitive EvolutionSchool of Biology
University of St. Andrewswww.st-andrews.ac.uk/~seal
Hominin stone tools
(Figure fromFoley, 1995)
Animal Traditions
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Genepool
Genepool
Gen
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Culture
Culture
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Development
Modifiedselection
Development
Modifiedselection
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 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).
“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 years…it is tempting to speculate that gene-culture interactions directly or indirectly shaped our genomic architecture.”
(Wang et al., 2006, PNAS p140).
Recent positive selection in the human genome
Edward O. Wilson
Cavalli-Sforza & Feldman Boyd & Richerson
Pioneers of gene-culture co-evolution
Gene Unit of cultural information
Gene pool Culture pool
Genetic inheritance Cultural transmission
Natural selection Cultural selection
Mutation Innovation
Random genetic drift Random cultural drift
Parallels between genetic and cultural processes
Natural and cultural selection
Other traits spread due to cultural selection (e.g. blue jeans, frisbee).
Some cultural traits have a direct effect on survival and natural selection may change their frequency (e.g. smoking).
Vertical
Parents
Vertical
Oblique
Parents Teacher, Leader, Elder
Horizontal
Vertical
Oblique
Parents
Friend
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.
Transmission biases
Human adults require the enzyme lactase to break down theprotein lactose that is present in cows’ milk.
Whether or not an adult can digest lactose is largely down towhether he/she possesses the appropriate copy of specific genes.
Dairy farming and lactose absorption
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)
Feldman and Cavalli-Sforza (1989) modelled the relationship between the spread of the gene for lactose absorption and thespread of the cultural trait.
Their analysis supported the hypothesis that the cultural practise of dairy farming created the selection pressure favouring this gene.
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.
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)
Applications of gene-culture models
Culturalevolution
HumanBehavioural Ecology
Contemporaryapproaches:
EvolutionaryPsychology
Gene-CultureCo-evolution
Historical approach
Human Sociobiology
Evolutionary approaches to the study of human behaviour
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Preference (P2)
Trait (T2)
Fisherian Runaway Sexual Selection
Kirkpatrick (1982)
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Preference (P2)
Trait (T2)
Unbiased Vertical Cultural Transmission
Cultural
Genetic
Laland(1994)
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Preference (P2)
Trait (T2)
Cultural++
+Biased Transmission favouring P2
The hypothesis could apply to many traits:
e.g. skin colour, facial features, facial and body hair, body shape, height, degree ofcharacter symmetry, degree of neoteny, level of aggressiveness, emotionality
Predictions and applications
There should be society-wide correlations between culturally transmitted preferences and gene-based traits (in both sexes)