Transcript comparative

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