Kin selection, inclusive fitness and altruism

- "A chicken is just an egg's way of making another egg."

- "[L]egend has it that in a pub one evening Haldane told his friends that he would jump into a river and risk his life to save two brothers, but not one, and that he would jump in to save eight cousins, but not seven."

All organisms are "survival machines" for genes -- and the primary "function" of these survival machines is to facilitate the successful propagation of copies of the genes into future generations.

From any particular gene's point of view, it does not matter if copies of it are made by its own "survival machine" (i.e. by the individual in which it resides) or by another survival machine -- or even machines -- that shares copies of that gene (typically a relative or relatives of the individual in question):

[I]n 1964 W. D. Hamilton showed that because close relatives of an organism are likely to share more genes in common (not to be confused with "common genes," the opposite of scarce genes), the gene can also increase its evolutionary success by promoting the reproduction and survival of these related individuals. This leads individuals to behave in a manner maximizing their inclusive fitness, rather than their individual fitness. [link]

Thus, in an (not necessarily conscious) effort to aid in the propagation of their own genes, individuals show altruism and favoritism toward relations with whom they share some portion of their genes.

From Steve Sailer:

One of the basic laws of modern evolutionary science, quantified by the great Oxford biologist William D. Hamilton in 1964 under the name "kin selection," is that the more close the genetic relationship between two people, the more likely they are to feel loyalty and altruism toward each other. Natural selection has molded us not just to try to propagate our own genes, but to help our relatives, who possess copies of some of our specific genes, to propagate their own.

See also: W.D. Hamilton works