Evolution of Behavior - (First Part)
OUTLINE
	A.  Evolution
		1.  Tenets of selection
		2.  Directional Selection
		3. Units of selection: species vs individual vs gene
			a.  Thought experiment: social conflict
				Hawk versus Dove?
				Evolutionarily Stable Strategies

	B.   Inclusive fitness
		1.  Altruism: acting against individual self-interest
			a) Kin Selection and inclusive fitness
			b) reciprocal altruism
			c) vulnerability of group selection

Reading: Dawkins book:  Skim chapters 1,2,3,;  Read 4,5
Then (inclusive fitness) chapters 6,7,10  [For discussion: 11, Eibl-Eibesfeldt] 

Principles of Behavioral Evolution
Basic Tenets of evolutionary theory provided by Darwin's Origin of the Species:

1.  Organisms produce more progeny than can survive
2.  Sexual reproduction leads to variation in genotype  (ALLELES)
3. Variation in Genotype -> variation in Phenotype  (TRAITS)
4. Traits are inheritable
5. Environment SELECTS for/against particular traits
6. Individuals with different traits reproduce differentially

Selection can change in a number of ways:
1. DIRECTIONAL: Adaptation
2. DISRUPTIVE: Divergent evolution  (SPECIATION)
E.g.,  body size in protection/holes;   tendency to flee or fight
3. CONVERGENT EVOLUTION:
e.g. psychological: classical conditioning in us and aplysia 
)
**But evolution not national championship/world series with TEAMS selected for success
-Teams can be destroyed, yet success goes on: Divergent evolution

Although evolution portrayed so far as working on species aggregates, this is not quite true.  Species is a category we impose.  Not the real unit of selection

WHAT IS THE UNIT OF SELECTION?
The Individual??         
Not necessarily:   Individual is merely the unit on which forces of selection act.
GENE is the unit that competes for selection;  the unit which can be selected and PRESERVED
Thought experiment example:  
Maynard-Smith's  EVOLUTIONARILY STABLE STRATEGY   =  strategy which if coded is at least as good as others.      Ex:  Fight or Flee:  agonistic (apotreptic) social behavior
Most simple possibility:   2 choices - be a fighter or a pacifist:  HAWK vs DOVE
As population fluctuates,  at some point, hawk value = dove value
 Then both are ESSs  (at 7/12  hawks 58%  to 5/12 doves 42% in Dawkins; each gets >6 pts)
The same ratio emerges in the behavior of a SINGLE individual if we allow it to try different strategies.
Could make more real still:
1.  More flexible strategies
	Retaliator - Threatens like dove, never attacks; but fights if attacked
	Bully - Attacks like hawk; but runs away if fights back
	Prober-Retaliator - Like retaliator but occasionally attacks first
(R and P-R do better than B)
2. Make time more costly:
3.  Unequal opponents -- must estimate chances
4.. Make context important: fight in certain conditions only
	Dawkins discusses in Chapt 5 (Aggression)

The POINT is that genes can be selected appropriately for all conditions
1.  Evolution can select both TYPE of behavior and, if individuals are behaviorally  flexible,  can select the QUANTITY or TENDENCY to perform each
2.  What is best depends on what else is around
3.  What is best for GENE stability may not be best for SPECIES 

EVOLUTION OF ALTRUISM
Traits that perpetuate Gene will flourish     --   WHO CARRIES the physical code doesn't matter to gene (Gene=info: like a computer program, or video pattern):  
The INCLUSIVE FITNESS of gene is what matters

KIN SELECTION  & EVOLUTION of altruism
Depends on:
1.  Percentage Genes shared  between actor and recipient 
2. Quantity benefit to recipient  fitness  
3. Quantity cost to actor

Altruism when   Gain Recipient / Loss actor   >  1/r
where r = Sigma  (1/2) # genetic links
Real-life KIN SELECTION PREDICTIONS:
1.  Altruism strongest between relations
2.  Groups that show altruism should have LOW KIN DISPERSAL
3.  Groups that show altruism should EITHER
	a.  Live in small close-knit all-kin groups  OR
	b.  have ABILITY to RECOGNIZE KIN among larger group

Kin Selection is the major  way to get altruism by "selfish gene" selection
There are 2 other ways

1.  Reciprocal Altruism
2.  Group Selection 	
	(Group selection is theoretically possible but vary vulnerable and perhaps nonexistent).
B2  SEXUAL SELECTION.
Why are there two Sexes?      
Of course we know that sex results in useful genetic recominations in reproduction.
But why are there so many behavioral concommitants to sex?  Why are there behavioral mating systems in which the two sexes play different roles, whyare there differences in sex roles in parental behavior and in social organization for many species?  Why do the two sexes sometimes have  physical differences in markings, body size, etc?

The hypothesis that genes are the units of selection, capable of coding behavioral traits, carries implications for SPECIFIC PATTERNS of sexual and parental behavior:

The 'selfish gene goal' is the same for both sexes:  Make as many copies of offspring genes as possible in future generations
The behavioral strategy entailed is simple for PRECOCIAL species: each sex produces many gametes and abandons the offspring.
More complex for ALTRICIAL species.   Which parent cares for the young?  WHY?

INTERSEXUAL SELECTION
Part of the answer may arise from disparities between the sexes in resources that are contributed toward the offspring. Although both sexes contribute equal genes, one sex (often the female) contributes a disproportionate share of resources.  Even in gamate size, eggs are larger than sperm.  In mammals, an even larger contribution in resources is made by the female through prenatal nourishment and protection.

INEQUALITY IN INVESTMENT leads to 2 pressures that constrain the options of the parents.  They may not be in equal positions in terms of consequences of choosing to leave and make new offspring with another mate:
1. MAJOR STOCKHOLDER pressure.
	Larger initial investment commits to greater future investment, because will need more to try again.
	ALTRUISTIC parent would stay, even if they make only a small investment, since offspring share genes;  but genes may do better by leaving young in mother's care and going off to make more offspring.  This might foster abandonment & serial mating
2. HOT POTATO  pressure
	The parent who is last in possession of the offspring faces more dire consequences if he/she abandons the offspring after his/her mate already has.

POLYGAMY VS MONOGAMY PRESSURES
If 2 sexes are not EQUALLY vulnerable, the above pressures may push exploitation towards POLYGAMY of some sort:
 POLYGYNY or  POLYANDRY

Selfish gene pressure towards exploitive polygamy may always be present.
But some environmental pressures may require monogamy in spite of polygamous pressures.
Examples:
1. High Energy needs/ low resource density
2. High Predation risk

INTRA-SEXUAL SELECTION

In Polygamy, females who make large investment may gain the advantage of mate choice
Males who make  small investment must compete among each other for access:
In polyandry, the situation may be reversed.
But even members of the sex that makes the large investment may need compete among each other for mate/resource quality (Ex:  Dawkins' South American birds)

B 3.   PARENT/OFFSPRING CONFLICT
Parental investment changes in importance as offspring grows
Importance decreases equally for both parent and offspring, but from different baselines.
Conversely, relative gain of producing a second offspring remains equal for parent and first offspring.
For both parent and first offspring, eventually a time arrives when it is to their genetic benefit for the parent to switch parental care to a second offspring.  But this moment arrives at different times for the parent and first offspring.  During the interval between those times, parent/offspring conflict exits.