Kin Selection
One reasoning behind altruism in the wild is kin selection, first coined by John Maynard Smith in 1964. Kin selection is the evolutionary strategy in which an individual would sacrifice their own reproductive success and survival in order for their relatives to be successful. Reeve et. al (1990) speculate that " a knowledge of intracolony genetic relatedness...is essential for understanding whether or not close kinship underlies the extreme reproductive selflessness displayed by subordinate mole-rats." Hamilton's rule is used to determine the benefits of altruism to an individual when the relatedness (r) compounded by the benefits to others (B) outweigh the costs to the actor (C). The coefficient of relatedness (r) is the probability that two individuals will both have copies of a particular gene by descent (Dr. Hoffman, 2015). The coefficient of relatedness for parents and offspring is 0.5 while for grandparents and grandchildren, the coefficient is 0.25. Hamilton's rule supposes that an individual will be more altruistic for a close relative rather than a distant relative.
Reeve et. al (1990) analyzed the DNA fingerprint of four wild-caught colonies (n=50 individuals) of Naked Mole Rats in Kenya and found that the fingerprints "of colony-mates were strikingly similar and that between colonies they were much more alike than fingerprints of non-kin in other free-living vertebrates." The mean intracolony relatedness estimate was 0.81 which is significantly greater than the expected 0.5 coefficient for siblings. The experimenters theorized that formation of new colonies through fission, inbreeding, and frequent colony extinction (through disease or predation) as well as the lack of copulation diversity, with only one breeding female and few breeding males, caused the lack of genetic variability in the mole-rat colony.
How could a community lacking genetic diversity be an advantageous species? Reeve et. al (1990) proposed that ecological factors, such as food resources and arid habitats, and genetic factors, such as increase relatedness among siblings through inbreeding, account for "the evolution of cooperative breeding and eusociality." Emilio A. Herrera takes a different outlook on why naked mole rats are eusocial. He states that one ecological factor "is common to all known cases of male-female eusociality: all presently live, or evolved, inside their food," and mole-rats are not different (2012). The threat of predation causes colonies of naked mole rats to stay underground where they feed on tubers and "only their close kin to mate with, high inbreeding occurs" (2012). In cases of extreme altruism, kin selection is central and relatedness coefficient is very high as in the societies of naked mole rats, bees, termites, and other insects.
Reeve et. al (1990) analyzed the DNA fingerprint of four wild-caught colonies (n=50 individuals) of Naked Mole Rats in Kenya and found that the fingerprints "of colony-mates were strikingly similar and that between colonies they were much more alike than fingerprints of non-kin in other free-living vertebrates." The mean intracolony relatedness estimate was 0.81 which is significantly greater than the expected 0.5 coefficient for siblings. The experimenters theorized that formation of new colonies through fission, inbreeding, and frequent colony extinction (through disease or predation) as well as the lack of copulation diversity, with only one breeding female and few breeding males, caused the lack of genetic variability in the mole-rat colony.
How could a community lacking genetic diversity be an advantageous species? Reeve et. al (1990) proposed that ecological factors, such as food resources and arid habitats, and genetic factors, such as increase relatedness among siblings through inbreeding, account for "the evolution of cooperative breeding and eusociality." Emilio A. Herrera takes a different outlook on why naked mole rats are eusocial. He states that one ecological factor "is common to all known cases of male-female eusociality: all presently live, or evolved, inside their food," and mole-rats are not different (2012). The threat of predation causes colonies of naked mole rats to stay underground where they feed on tubers and "only their close kin to mate with, high inbreeding occurs" (2012). In cases of extreme altruism, kin selection is central and relatedness coefficient is very high as in the societies of naked mole rats, bees, termites, and other insects.
The heading photography is from http://www.the-scientist.com/?articles.view/articleNo/32136/title/Underground-Supermodels/.