From Genes to Behavior: Outline

Transcription

1 Recap from last time A genes-eye-view of natural selection implies considering a trait s 1. effect on kin (inclusive fitness) 2. effect on mating success (sexual selection) Controversies remain about 1. the importance of group selection (partial resurrection) 2. the selective pressures favoring cooperation among non-kin in humans

2 From Genes to Behavior: Outline Review of Ridley Gene-environment interactions: norms of reaction tanning, geckos, soapberry bugs Violence, MAOA and Upbringing epigenetics Ease of learning: selection shapes what we learn, and when heritability Garcia: why does a reinforcer reinforce? What do infants attend to? Sensitive period learning

3 Discussion of Ridley Tale of two voles: monogamous (prairie) polygynous (montane) What makes them behave differently?

4 Discussion of Ridley Tale of two voles: monogamous (prairie) polygynous (montane) What makes them behave differently? Vasopressin/oxytocin: hormones promotes social bonding Prairie vole: mutation in gene for vasopressin receptor (promotor region) changes expression of gene in different parts of brain

5 Discussion of Ridley Tale of two voles: monogamous (prairie) polygynous (montane) What makes them behave differently? Vasopressin/oxytocin: hormones promotes social bonding Prairie vole: mutation in gene for vasopressin receptor (promotor region) changes expression of gene in different parts of brain SO: a change in a single gene affects monogamy or polygyny!

6 Discussion of Ridley (continued) Some questions: what happens to montane vole (and mice) given prairie vole receptor gene?

7 Discussion of Ridley (continued) Some questions: what happens to montane vole (and mice) given prairie vole receptor gene? they became more affiliative with their mated partners

8 Discussion of Ridley (continued) Some questions: what happens to montane vole (and mice) given prairie vole receptor gene? they became more affiliative with their mated partners Do they also need an environmental signal to release vasopressin?

9 Discussion of Ridley (continued) Some questions: what happens to montane vole (and mice) given prairie vole receptor gene? they became more affiliative with their mated partners Do they also need an environmental signal to release vasopressin? Sex release of vasopressin male gets addicted to his mate. So environment matters too

10 How to think about genes and environment: Norms of reaction norm of reaction: expression of a genotype in different environments Response is shaped by selection

11 Norms of reaction: sex ratio in leopard geckos Leopard gecko nature: more males to be born when the temperature is high

12 Norms of reaction: Mate-guarding in Soapberry bugs When is it adaptive for bugs to mate-guard?

13 Norms of reaction: Mate-guarding in Soapberry bugs When is it adaptive for bugs to mate-guard?

14 Violence and MAOA Imagine: you study people with antisocial behavior You find their levels of MAOA (monoamine oxidase) are lower than controls biological determinism?

15 Violence, MAOA and Upbringing

16 Violence, MAOA and Upbringing: two reaction norms

17 Epigenetics human and chimp genomes nearly identical Difference: gene expression in development liver and skin cells contain same genes; not all expressed. Why?

18 Epigenetics human and chimp genomes nearly identical Difference: gene expression in development liver and skin cells contain same genes; not all expressed. Why? Epigenome: chemical markers that prevent expression (CH 3 etc) What affects the epigenome?

19 Diet, BPA and the agouti mice Agouti gene makes mice ravenous, diabetic, and yellow. What did offspring of moms with agouti gene look like?

20 Diet, BPA and the agouti mice Agouti gene makes mice ravenous, diabetic, and yellow. What did offspring of moms with agouti gene look like? on normal diet: most looked like mom on diet with methyl donors (onions, garlic, beets): healthy on diet with BPA?

21 Diet, BPA and the agouti mice environmental influences affect gene expression throughout life

22 Epigenetics: Behavior also affects the epigenome Michael Meaney: 2 kinds of mother rats nurturing rat moms (licked babies): brave, calm babies neglectful rat moms: nervous, fearful babies Genetic or epigenetic? Meaney thinks epigenetic: licking removes methyl groups from pups DNA, activates genes involved in stress response How do they know it wasn t genetic? Pups born of low-licking mothers were placed with high-licking foster moms, and vice-versa * Mechanism still controversial

23 Ease of learning Learning biases: Another view of gene-environment interactions 1. Genes affect what you learn easily 2. Some things are easy to learn, others hard 3. Genes affect what you attend to And what you attend to is what you are likely to learn

24 Ease of learning: Garcia s experiments

25 Ease of learning: Attention in infants What you attend to is what you learn: faces are important

26 Ease of learning: Attention in infants Eyes are especially salient...

27 Ease of learning: Attention in infants...especially when those eyes are looking at you.

28 A brief note on heritability LESSON THUS FAR: WHEN TALKING ABOUT AN INDIVIDUAL, cannot separate genes from environment BUT, WHEN TALKING ABOUT A POPULATION: Geneticists do separate variation due to genes and environment heritability = proportion of phenotypic variance due to genetic variance 1. note: heritability only applies to a population 2. more environmental variance lowers heritability

29 Summary Genes don t do anything unless they are expressed Epigenetic switches control gene expression Environment and behavior affect that expression (agouti mice, upbringing) Reaction norms summarize how a genotype is expressed in different environments Reaction norms the response of the gene is genetic Genes also affect learning and attention in adaptive ways