Cultural Evolution

1. Cultural Evolution

2. Potential examples of animal culture • Potato and grain washing in macaques • Imo • Cream pilfering in blue tits • Gull hunting in captive orcas

3. Social influence and culture • Inadvertent social information (ISI) use can produce differences among populations • E.g., mate choice copying • Natural selection requires • Variation in a trait • Fitness implication • Transmission • Not necessarily heritability!

4. VE reconsidered I • Recall… • VP = VE + VG • Does VE account for all environmental variance? • VE = VDE + VAE + VAP + VAS • A = “additive”: variation is transmitted to offspring • Fulfills transmission requirement of selection • VDE direct influence of environment • VAE results from genotypic / environmental associations • E.g., Inheritance of a territory, influences of prior niche construction • Influence parent offspring regressions: lumped into VAG if not considered explicitly

5. VE reconsidered II • VE = VDE + VAE + VAP + VAS • VAP results from parental effects • E.g., the maternal environment, milk content, paternal care… • Late effects can be controlled by partial cross-fostering • Early influences are ~ impossible to control • Generally end up (inappropriately) lumped with VAG • VAS results from social influences • E.g., ISI, teaching… • Additive effect can be very strong • Will be treated as VAG unless social influence is controlled

6. Transmittability • Why limit our interest to heritability (VAG/VP) if selection and drift operate on components other than VAG? • Transmittability = (VAG+VAE+VAP+VAS+VS*G) / VP • Where VS*G is the genetic predisposition for social learning • Measures the evolutionary potential of a population in terms of phenotypic change, whatever the mechanism of transmission

7. An evolutionary definition of culture • “Culture is the part (VAS) of phenotypic variance that results from information transmitted across generations through social influences” • Cultural traits: • Social learning • Transmitted across generations • Generalized across situations • Long term modification

8. Social learning • Learning: An adaptive change in behaviour through the effect of acquired information • Includes imitation, copying, teaching, etc. • Strong role of ISI From Nordby et al. 2000 Animal Behaviour 59:1187-1197

9. Transmission across generations • Horizontal transmission alone does not result in tranmittability • Successive generations must interact to produce culture • Salmon returning to their natal streams is not a cultural trait • Culture is only part of non-genetic transmittability

10. Generalization and durability • Generalized female choice • Short lasting social influences will not tend to be transmitted

11. Notes on culture • Requires overlapping generations • Some non-genetic transmittable information does not produce culture • Parental effects • Territorial inheritance • Niche construction • Cultural transmission vs. parental effects • Learning implies cognition • Cultural traits can be transmitted horizontally and obliquely

12. Population memetics • A meme is “that which is copied” • Individuals acquire memes (learn) and transmit them (culture) • Mutate rapidly, non-randomly • Horizontal transmission homogenizes groups • Increases differences between groups • Can lead to group-level selection • The tax meme • Dominance of cooperative memes can be enforced by moralistic aggression

13. Teaching • Individual A modifies its behavior only in the presence of naïve observer B • A receives no immediate benefit or incurs a cost • A’s behavior results in B acquiring knowledge or skills more rapidly than it would have in the absence of A Older pup calls Younger pup calls

14. Bird songs and culture • Geographic variation in bird songs • True dialects • The four criteria • Learning • Across generations • Lasting modification • Generalized (?) • Arguably the strongest animal example of culture in non-humans • Effects on female choice, speciation? From Wilson et al. 2000 The Condor 102:355-364