selfishness and altruism

Social behavior can be

Heritable

How can an action/phenotype that lowers the actor’s fitness be

“beneficial”?

Altruism ex. Caring for kids with resources instead of using the resources yourself because they carry your genes

Kin selection

Inclusive fitness – dependent on both direct and indirect fitness

Whether or not you act altruistic to someone depends on how closely related you are

Hamiltons rule

Br - C > 0

B is benefit to recipient

r relatedness between actor and recipient

C cost to actor

> 0 then should do the act

<0 should not do the act

Ex. Prairie dogs give out call to warn others of predators but puts them self at risk so they usually do this when they are in a population where they have more kin

Green beard alleles

Identifying kin

an allele that simultaneously produces a phenotype (a green beard), allows recognition of the phenotype in others, and initiates altruistic behavior towards them

All three requirements met means high beneficial so should be selfish

Selfish genes

enhance their transmission at expense of other genes

• Meiotic drive, segregation distorters, MITOCHONDRIA!!!, etc.

Selfish mitochondria

Decreased energy

• Replicated faster/more often

• “moral hazard” hypothesis: passed on more but might not produce most energy for cell

• “Mother’s curse”: maternal inheritance so select for having high fitness in daughters but low fitness in sons so it’s beneficial

Eusociality

Ultimate form of altruism

• “Castes” of nonreproductive that help raise young

Evolve by kin selection and haplodiploidy hypothesis

Haplodiploidy hypothesis

• Sisters are more closely related than they would be to offspring

• Higher fitness for helping raise sisters than making your own offspring

• Largely refuted because eusocial species don’t have haploid diploid sex determination

Monogamy hypothesis

• If you know your sibs are full sibs, they are as closely related to you as your own

offspring

• Similar problems as haplodiploidy

Ecology and life history hypothesis

Best one

• All eusocials have “fortress” nests and larvae that require lots of care

• Hard to go it alone

• Vespid wasps and gradations of eusociality

Reciprocity

• Non-kin selection

• Social networks

• Punishment is important punishment selfish moochers

Do something good for me and I’ll do something good for you

Can Hamilton’s rule explain spite?

• B is negative

• Yes, if r is negative too

B and r negative makes positive and offset costs

• Better for the average to reproduce than the recipient

Hamilton and controversy

• Eugenics

• Lack of natural selection in modern humans