Altruism is defined as giving up personal reproductive success
to increase the reproductive success of some other individual
Selfishness is the opposite where individuals maximize their own RS and the rest of the species be damned
How can alturism evolve? We expect selfish genes to spread through populations, and altruistic ones to disappear.
Are there animals that exhibit altruistic behaviors? obviously yes
Altruism is most often directed to genetic relatives: (nepotism)
r = the coefficient of relatedness, means the average proportion of genes shared between two individuals by common descent; alternatively the probability of sharing a particular gene from a common ancestor.
calculated by number of meioses separating two individuals (here insert
parent/offspring chromosome
set diagram)
People pay attention to these relationships (here insert family tree)
How can individuals increase their fitness? (spread of traits and the genes that cause them through populations)
direct selection ? production of offspring and descendant kin
kin selection ? assisting collateral relatives to produce non-descendant
kin
helping relatives can spread through populaitons if individuals transmit more copies of their genes into the next generation by doing so than by not doing so
The fitness effects of direct selection are refered to as personal fitness
The sum of fitness effects of direct selection and kin selection are referred to as inclusive fitness
Hamilton's rule C/B = r; C < Br; determines whether altruism can evolve through indirect selection
"I would gladly give my life for two brothers or eight cousins"
Darwin got it right. Natural selection acts on families: heritable
variation among families in altruistic behavior leads to differential reproductive
success and the spread of altruistic traits through populaitons