Adaptiveness of Behavior

• Genetics and evolution

• Learning

Evolution in a nutshell• Start with variability in genes, and thus in traits

• Add challenges the world poses to survival and reproduction

• Result: – genes/ traits that decrease chance of reproduction

get reduced in next generation– genes/traits that increase chance of reproduction get

increased in next generation

Functionalist perspective

• Physical and behavioral traits come about in the course of evolution because they promote survival and reproduction

• Thus there must be a functional explanation for every trait/ behavior

Functionalist perspective

• Caution: – vestigial traits– traits as side effects of natural selection– chance variations (genetic drift)

• Some traits do not serve an immediate function, but they won’t killya!

Functionalist perspective• Caution:

– “Survival of the fittest”-- misconception of natural selection as guided by moral force

– term coined by Spencer, not Darwin– Misconception leads to “Naturalistic Fallacy”:

belief that natural =right, moral; that if natural selection favors a behavior, that behavior must be acceptable

– Examples?

Environment and evolution

• What is the color of the peppered moth?– pre-industrial revolution: trees covered with

light-colored lichen– air pollution killed lichens, trees became dark– anti-pollution laws cleaned up air, lichens grew

back

• Other examples happening right under our nose?

The Genetics of Behaviorgenes-units of hereditychromosomes-strands of genes; come in pairsdeoxyribonucleic acid-DNAribonucleic acid (RNA)-template for synthesis of proteinsroles of proteins??

Mendelian genetics

homozygousheterozygousdominant generecessive gene

Mendelian geneticsTraits caused by single gene:

- PTC taste- Phenylketonuria- SLI- dogs’ fearfulness

Variations of type, not degree

Polygenic Traits • influenced by many genes

• Differ in degree, fall on continuum

• distribution described by normal curve

• selective breeding can change distribution

Polygenic Traits

Eg: maze learning

Selective breeding • Alcohol consumption in mice• Anderson and McClearn (1981) measured ethanol solution

intake by fluid-deprived mice• Ratio of alcohol intake on test day/ to water intake on day

prior to test=ethanol acceptance score• mice with highest scores are mated, mice with lowest scores

are mated• 1st generation: mean scores of high/ low group:

0.74 0.87• 14th generation: 0.38 1.19

Genetic diversity, or: How unique are you

• Humans have __ pairs of chromosomes

• Imagine you only had 1 pair. How many different individuals could you produce through sexual reproduction?

Chromosome Pairs n=1

Mom Dad

You could get

possible gametes from each parent: 21 = 2

or from Mom and or from Dad

So you could be:

Possible genotypes: 22 = 4

or or or 1 in 4

M1 a b D1 a b

Chromosome Pairs n=2Mom: M1 M2

ab abYou could get:

M1a/ M2a or M1a/M2b or M1b/M2a or M1b/M2b from Mom AND

D1a/ D2a or D1a/D2b or D1b/D2a or D1b/D2b from Dad

Possible gametes from each parent:___

You could be: M1a/ M2a / D1a/ D2a or M1/a/ M2a / D1a/D2b or M1a/ M2a / D1b/D2a or …..

Possible genotypes:____

Dad: D1 D2ab ab

Chromosome pairs n=23• Possible gametes from each parent: 223

• Possible genotypes: 246= more than 70 trillion!

• Does not include variation due to crossing over, mutations

• We are SO unique!!!

However:

• Guesstimate: How many genes do we have?

• How many do bacteria have?

% relatedness- a closer look

Mom Dad

You could get

possible gametes from each parent: 21 = 2

or from Mom and or from Dad

or or or 1 in 4

M1 a b D1 a b

% relatedness- a closer look

• Refers to % chance of sharing a particular gene with someone

• Does NOT refer to the total amount of genetic information shared between two individuals

Species-typical behaviors

• Example 1: – red belly as sign stimulus for stickleback attack

• Example 2 – migratory flight in indigo buntings– birds migrate at night– Emlen (1975): birds caged outside make restless

futile movements towards south in fall, north in spring

Species-typical behaviors• Question 1: How do they tell direction? What

is their sign stimulus for migration?• Question 2: Is knowledge innate or learned?

– Materials:• as many buntlings as you wish

• as many undergrads as needed to watch them

• several months of nothing better to do

• a planetarium

Emlen’s deprivation experiments• 1. Block view of sky• 2. Block view of Polaris• How do they know to use Polaris?• 3. Raise buntlings in 3 groups

– group 1: no experience with night sky

– group 2: normal night sky

– group 3: fake sky with different fixed star (Betelgeuse)

– measured: orientation of movements when exposed to normal sky in fall

Emlen’s deprivation experiments• Findings:

• Group 1: no consistent orientation

• Group 2: away from Polaris

• Group 3: away from Betelgeuse

• Conclusion?