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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
Figure 6.6Fig 6.6
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 Montane Vole(Monogamous) Polygamous
Important applications?
•Insel and Young (1999) found difference in the gene that makes vasopressin receptors in monogamousand 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
Learning in Aplysia
Hearing in the barn owl
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 knife2. Your brain is a scheming despot3. Your brain is a culture medium4. 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 despotPrimates 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 mediumAt 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
have to have direct relationships with finding fruit or fleeing lions
Geoffrey Miller“The mating mind”