Lecture 2 (Evolution of Behaviour) 2023 PDF

The Evolution of Behaviour Tinbergen’s four causes 1. Ontogeny (development) Proximate 2. Immediate (within lifetime) causation (mechanism) 3. Function (adaptive value) Ultimate (over generations) 4. Evolution  Evo...

The Evolution of Behaviour Tinbergen’s four causes 1. Ontogeny (development) Proximate 2. Immediate (within lifetime) causation (mechanism) 3. Function (adaptive value) Ultimate (over generations) 4. Evolution  Evolution Biological evolution is the change in the properties (or gene frequencies) of populations over the course of generations What is a population? Divergence, speciation Common descent  Classification Taxonomic categories – Linnaeus’s binomial nomenclature, hierarchy – Originally based on physical similarities – Similarity in God’s plan Darwin: Populations (species) diverge – A new meaning to species’ relatedness Phylogenetic trees – Nodes, branches  Similarity and common ancestry  If species diverge after splitting, similarity should indicate relatedness - Simple version: Phylogenies are based on similarity  We now mostly use genetic characters to build phylogenies  Natural selection 1. If there is variation in a trait 2. … and the variation is heritable 3. … and the variation causes differences in reproduction 4. … then traits that promote reproduction (and the genes that code for them) will increase in the population  Breakout! Describe a scenario in which a population of rattlesnakes adapts to it’s environment by evolving longer fangs. Make sure to consider variation, heritability and selection.  A big problem with Darwin’s theory Selection acts on variation – Where does the variation come from? Blending inheritance – Variation decreases Mendel’s work – Particulate inheritance – Published in 1865, ignored until 1900 The Modern Synthesis 1930-1940’s Reconciled Darwin’s theory with Genetics Laid the foundation of our current Theory of Evolution  Evolution and selection Natural selection without evolution – Evolution requires heritable variation Evolution without natural selection – Mutation – Genetic drift Importance depends on population size Does not produce adaptation – Immigration / emigration Fitness! Fitness: Relative success of one type (genotype or phenotype) To adapt: (v) To evolve in response to selection (a population-level process) Adaptation: (n) A derived character that spread in response to selection Populations adapt But what if the environment changes? Adaptations (n) Derived characters that spread in response to selection Not all useful characters are adaptations – Ancestral characters Sutured skulls – Genetic hitchhikers – Evolved by drift – Exaptations May be further modified to become adaptations  Design, purpose, and natural selection Adaptations are often complex, functional, and seemingly designed Paley’s “watch on the heath” argument Selection produces order and functionality without having any goal – An automatic, subtractive process Function, purpose, and natural selection What is the function of a flower petal? The Is- Ought Fallacy Science attempts to explain “what is” What is ≠ What should be – Infanticide – Forced copulation – Enslavement Genotype, phenotype Genotype: An individual’s partial or complete genetic sequence Genome: All the genetic information carried by an individual Environment: Everything external to the genome Phenotype: The organism’s characteristics  Nature and nurture: What controls the phenotype? What does it mean that a trait is “genetic” or “environmental” or some combination thereof? – DNA in a dish Individuals, populations Variation explains variation  Environmental effects “Typical” environmental effects Developmental noise – Fluctuating asymmetry Maternal effects Epigenetic inheritance – Genomic imprinting – DNA methylation Analyzing selection 1. Compare traits with proxies of selection 2. Response to selection 3. The comparative method Proxies of selection Proxies of selection  Response to artificial selection  No points pop-quiz Which of the following statements about the silver fox domestication project is FALSE? A. The researchers used several criteria for selecting individuals to breed, including intelligence, friendliness, and morphological features. B. It has been hypothesized that the researchers were inadvertently selecting for low adrenaline levels, which, due to adrenaline’s relationships to other hormones, produced a cascade of unexpected effects. C. The experiment produced evidence that genes affecting behavior can also affect morphology. Response to natural selection  The Comparative Approach I Compare species Requires phylogeny Cool trick #1: Reconstruct ancestral characters – Hard to study behavior from fossils Learn the direction and order of evolution, the origin of characters The Comparative Approach II Cool trick #2: Test for evolutionary correlations Duetting evolves when birds don’t migrate  Behavior and Speciation Biological species concept Sexual signals as prezygotic isolating mechanisms Irwin et al. 2001 Nature 409 333-