Evolution wk 7 ! Fin for Dec 10th Flashcards
Hamilton ….
4 social interactions between 2 indivs.
- gains and losses in terms of fitness for the recipient and actor. matrix
altruism - actor loss, recipient benefit
Spite = actor loss, recipient loss
Mutualism, cooperation = actor benefit, recipient benefit
Altruism = actor suffers, recipient benefits
why cooperation is a problem
free riders share benefits but no the costs
(true for mutualism and for altruism)
kin selection.
why would showing altruism and mutualism to your kin make sense.
inclusive fitness theory. what is total fitness?
what is Hamilton’s rule?
“would i sacrifice myself for a brother? .. no, but i would to save 2 brothers or 8 cousins”
let’s say brother shares .50 DNA so saving one wouldn’t be beneficial
inclusive fitness theory
total fitness of an indivs genes =
- direct fitness: personal reproduction
- indirect fitness: reproduction by relatives
Hamiltons rule: act has a cost for actor and benefit for recipient.
cost/benefit analysis
the spread of an altruistic gene occours when:
c>rb
b= benefit to recipient
r = coefficient of relatedness
c=cost to actor
Kin selection
imagine everyone in your family has Greenbeards. You would be kinder to people who are closely related to you
why be kind to nonkin
for good of species ?
For the good of the species ?
- classical group selection (Wynne-Edwards)
Critiqued by George Williams + Maynard Smith
problem
- benefits have to go to the individual
how can kin selection be used to explain altrusitic behaviour in animal kingdom
explains the evolution of sterile worker castes such as naked mole rats and honey bees
solution to problem of Kind to nonKin
Trivers (1971)
Trivers (1971)
- reciprocal altruism
- direct reciprocity
- costs should be lower than benefits
- benefits should be delayed!!
Requirements
- interact often
- be able to recognise one another and keep accounts
- be able to act contingently
e.g. I look after your kids, you cut my grass
exaples of direct reciprocity in the wild
very rare. Not found in chimps.
Wilkinsin found
vampire bats regurgitate blood to colony mates. Especially ill bats.
- because of reciprocity.
Mutualism (coorperation)
(in kind to non kin)
many supposed altruistic actions might actually be mutualistic
e.g. cooperative hunting
- But free riding and exploitation can still be problems
e.g.
direct immediate benefits do not require reciprocity (no delay in benefits).
e.g. monkeys grooming get food
begging and threatening are coercive and impose costs on the actor.
indirect reciprocity
- helps others to build a reputation (downstream)
FINISH
generalised reciprocity
help others bc it feels good.
altruism without expectation of return
difficult from a evolutionary point of view
Negative reciprocity
- punishment
- inflicting harm for harm donw
- important for detering free riders
- third-party punishment particularly important and possibly uniquely human
- Chimpanzees don’t do it, but human children do (even from their own child)
strong reciprocity
- cooperate with othres and punish non cooperators
reciprocity in humans
essential for hunter gatheres
- e.g. FINSIH
- fair sharing of resources
- receiving and destroying gifts
Cultural group selection
groups of cooperators are more succesful than non.
FINI
