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Evolution of brain and behaviour Chapter 6 Why compare? • The engine of evolution • comparing brains • why compare? – Picking special cases – interesting model systems – knowing where we came from Early view of classification and evolution -the great chain of being Natural selection 1. Mutations happen 2. Some mutations increase likelihood of reproduction 3. Individuals which possess such mutations should increase in number A painful evolution of ideas Huxley: Of course I was in a considerable rage … I was going to walk past, but he stopped me, and in the blandest and most gracious manner said ‘I have received your note. I shall grant it.’ The phrase and the implied condescension were quite ‘touching’ so much that if I stopped for a moment longer I must knock him into the gutter. I therefore bowed and walked off. Round II Wilberforce: …”is it through your grandfather or your grandmother that you claim descent from a monkey?” Huxley: “I am not ashamed to have a monkey for an ancestor: but would be ashamed to be connected with a man who used great gifts to obscure the truth” ...one lady fainted and had to be carried out…. The hippopotamus minor Lest we feel smug…. Modern classification Nervous systems can vary enormously Fig 6.6 6.6 Figure Comparing brain structures Fig 6.11 But mammalian nervous systems are very similar Fig 6.7 Fig 6.7 Species comparisons can yield insight into brain function •This is most effective when done with closely related species •We look for two species have much phylogeny in common but some marked difference in behaviour A case study in comparative psychology: Parental behaviour in voles Prairie voles Pup retrieving Fighting intruders Voles and vasopressin Prairie Vole (Monogamous) Montane Vole Polygamous Important applications? •Insel and Young (1999) found difference in the gene that makes vasopressin receptors in monogamous and polygamous voles •Inserting DNA from monogamous vole vasopressin receptor into a mouse makes a more sociable mouse •vasopressin receptors are found in the primate brain •many psychiatric disorders involve problems with sociability (schizophrenia, autism, for instance) Voles, sex and space Picking special cases Squid giant axon Hearing in the barn owl Learning in Aplysia Knowing where we came from Homeothermy rules Fig 6.12 An exceptional mammal Fig 6.12 An exceptional primate Brain size increase is not homogeneous Fig 6.15 Hominid evolution Fig 6.15 Specializations of the human brain •Larger representations of the hands •neocortical specializations for speech •extreme hemispheric specialization •expanded prefrontal cortex Sexual selection: The second great engine of evolution 1. There’s no point in living if we don’t get to have sex 2. In order to have sex, we must be chosen by a member of the opposite sex Theories to account for brain expansion in humans 1. Your brain is a Swiss Army knife 2. Your brain is a scheming despot 3. Your brain is a culture medium 4. Your brain is a Las Vegas hotel suite Your brain is a Swiss Army knife -this is the predominant view of evolutionary psychologists -your brain is a collection of specialized cognitive devices that are designed to solve specific problems -problems may be difficult to recognize and processes may be co-opted for other means Steven Pinker has popularized this view Problem: Many of the things that we do with our brains are hard to reconcile with the kinds of tools needed to find food or flee lions Your brain is a scheming despot Primates are distinguished from all other animals by their scheming, Machiavellian politicking, thieving, lying and murderous deception. -much of this notion is driven by observations of primate behaviour -there are no better schemers than us -theory is that our great cerebral hemispheres (especially perhaps the frontal lobes) have evolved help us with ‘social intelligence’ – a euphemism for Machiavellian scheming. Niccolo Machiavelli “No enterprise is more likely to succeed than one concealed from the enemy until it is ripe for execution.” Your brain as a culture medium At some point in our evolutionary history, we crossed a threshold when we had enough cerebral ‘stuff’ to produce culture. Culture can be thought of as a kind of unit of mind that is independent of bodies (memes). Culture and the brains that support it entered a kind of positive feedback cycle – brains better at propagating memes succeeded. E. O. Wilson – originator of sociobiology, the forerunner of evolutionary psychology Your brain as a Las Vegas hotel suite Sexual selection -it’s no good surviving if you don’t have sex -to have sex you need to attract a mate -if there is variability in mating success, then the traits that promote that success will be strongly selected for -what if many of the things that we consider to be uniquely human were sexual ornaments like the tail of the peacock? -this would mean that such traits would not Geoffrey Miller have to have direct relationships with finding “The mating mind” fruit or fleeing lions