Inclusive Fitness

Question 1

How does cooperation arise?

Answer 1

Darwin : Selection may be applied to the family

Kropotkin : cooperation made the success of species

Fisher: Neo-darwinism, natural selection, Mendelian genetics and population genetics

Hardane : relatedness and altruism

Hamilton : his rule rb>c , inclusive fitness = direct + kin-selected (indirect fitness)

Question 2

Hamilton’s table of social interactions

Answer 2

mutually beneficial (++)
altruistic (-+)
selfish (+-)
spiteful (–)

Question 3

Cooperative behaviour

Answer 3

benefits another individual and has been selected for, at least in part, because of its beneficial effects on the recipient

Question 4

Mutualistic cooperation

provides immediate or delayed benefit to actor’s fitness

Answer 4

Altruistic cooperation

- cooperation is costly to the fitness of the actor

Question 5

Inclusive Fitness Theory can be applied to

Answer 5

actions whose effects on recipients are negative rather than positive

Question 6

In practice, inclusive fitness is hard to measure…

Answer 6

…but there are good examples

Question 7

Altruism evolves if:
rb > c
rb – c > 0

Answer 7

r = relatedness
b = benefit to recipient
c = cost to actor

Question 8

The problem of measuring fitness…

Answer 8

Solutions
Productivity of offspring, not adults, in lifetime
Snapshot of productivity
		- single season or reproductive attempt
		- offspring condition
		- mating success
Survival across a discrete time interval
Energy budget, food intake, etc…

Question 9

The evolution of life on earth entails a series of major transitions in complexity:

origin of chromosomes
origin of eukaryotes
origin of sex
origin of multicellularity
origin of social groups
origin of human society/language

Answer 9

Each transition involves cooperation, so social evolution theory explains each transition using the logic of inclusive fitness theory

Question 10

The origin of multicellularity

Answer 10

Hypothesis: High relatedness between cells played key role in transition to multicellularity

Question 11

Origin of multicellularity experiment (Ratcliff et al. 2012)

Answer 11

Selected for multicellularity in unicellular yeast:
Saccharomyces cerevisiae
Multicellular traits: 	
- deferred reproduction
- division of labour (apoptosis)

Multicellular clusters form by clonal adhesion (high r) not aggregation (low r)

Question 12

Origin of multicellularity

Answer 12

Obligate v. facultative multicellularity (commitment)

Number of cell types (specialisation)

Probability of sterile cells (altruism)