Transcript Slide 1
Review Evidence in favor of evolution by natural selection: 1. Existence and pattern of the fossil record. 2. Homology. 3. Universality of genetic code. 4. Analogy with plant and animal breeding. 5. Direct observation. 6? Adaptations? -Evolutionary approach to brain, mind and behavior -Proximate vs. ultimate -Mind is specialized -Mind is not a blank slate (language, face recognition, sexual desire, mate choice, parental solicitude… -Human nature causes culture; it is not caused by culture: universals. -Natural selection occurs when replicating entities have high copying fidelity relative to their differential rates of replication. -Natural (and sexual) selection builds adaptations that are: built of existing variation (mutations). often formed slowly often formed cumulatively specialized costly may be out of date -Natural (and sexual) selection builds adaptations that are good for: The species? The group? The individual? The gene? S SS S SS S S S SS S A A A A AA A AAA A SAS S S AA A SSA S SS S SS S S S SS S S SELFISH MIGRANTS CAN INFECT A GROUPS A A A A AA A AAA A S AND CONVERT THEM INTO MIXED GROUPS SAS S S AA A SSA S SS S SS S S S SS S S SELFISH MIGRANTS CAN INFECT A GROUPS A A A A AA A AAA A S AND CONVERT THEM INTO MIXED GROUPS WHICH BECOME PURE SELFISH GROUPS SAS S S AA A SSA WHICH TEND TO GO EXTINCT S SS S SS S S S SS S S SELFISH MIGRANTS CAN INFECT A GROUPS A A A A AA A AAA A S AND CONVERT THEM INTO MIXED GROUPS WHICH BECOME PURE SELFISH GROUPS SAS S S AA A SSA frequency Evolution by Natural Selection tends to make the mean phenotype converge on the optimum. trait value Sexual Selection Type of natural selection. Selection builds adaptations of all types. Sexual selection builds adaptations that increase mating success: 1. more mates 2. better mates Challenges for ancestral males: quantity. Challenges for ancestral females: quality. Likely to produce divergent adaptations: Two optimal phenotypes Sex differences parallel those in other primate species. Facultative adaptations: monitor environmental variation and adjust phenotype accordingly. Selection favored genes that produce the right pattern of environmental responsiveness The effects of experience are preprogrammed by natural selection. Violence: Genetic fallacy: Traits shaped by evolution (biology) are fixed and inflexible. Oh really?!? What about facultative traits? Norm of reaction tells you how to change the trait. Two nature/nurture questions! 1.Why is my skin this color? causes of development (interaction) 2. Why do people differ in skin color? causes of variation (partition the variance) If we want to know how heritable a trait is… h2 = Vg/Vp, thus h2 = Vg/(Vg+Ve) h2 varies from 0 to 1. Selection is more effective when heritability is significant; but selection typically reduces heritability as it works. Heritability of facultative traits? Relatively low because of response to environment. But obviously designed by selection! Nature/nurture is misleading! Mendel’s hypothesis about the stuff of heredity: 1. Particles, not fluids (genes). 2. Adults have a double dose of particles (diploid adults). 3. Adults give only half of their double dose to each offspring (haploid gametes). 4. Some particles have stronger effects than others (dominance). Gene expression: How genes specify the recipes for proteins Genetic variation and phenotypic variation Naturalistic fallacy: what’s natural is good. Oh really!?! tsunamis, disease, aging and death… Understanding is not rationalizing. In the case of facultative traits understanding points the way to change.