Evolution of brain and behaviour Chapter 6. Why compare? The engine of evolution comparing brains...

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”