Kinship and Social Evolution

Vocabulary terms and concepts regarding biological kinship, altruism, inclusive fitness, and social structures like eusociality based on the lecture notes.

Kin

The term used to refer to family members.

Altruistic behaviors

Helping others even though there may be a cost associated with that help. EX. giving a warning call to others when predator spotted.

Direct fitness

The number of offspring an individual has.

Indirect fitness

The number of offspring that an individual's relatives have.

Inclusive fitness

The sum of an individual's direct fitness and indirect fitness.

Kin selection

A theory developed by W.D. Hamilton in the early $1960\text{s}$ proposing that animals should help blood relatives because they share genes, which increases the individual's own indirect fitness.

Coefficient of relatedness

A measure used to calculate how many genes kin share; for example, it is $0$ for unrelated individuals and $.5$ ($50$%) for parents and their offspring.

$.25$ ($25$%)

The coefficient of relatedness shared by half siblings, aunts/uncles, nieces/nephews, and grandparents/grandkids.

$$1/8$$

The fraction of genes shared by cousins, which historically served as the basis for marriage laws to avoid inbreeding.

(r \times B) - C > 0

Hamilton's formula predicting that an altruistic trait will spread if the relatedness ($r$) multiplied by the benefits ($B$) minus the cost ($C$) is greater than zero.

When r if high, greater benefit of altruistic behaviour.

Family dynasties

A phenomenon seen in many birds where families that control high-quality resources remain on territories longer and are more stable than those with low-quality resources.

Cooperative breeding

Also known as "helping at the nest," this is a behavior where close genetic relatives, such as Florida scrub jays, help raise their siblings rather than reproducing themselves.

Eusociality

The most complex social system, which requires individuals to cooperate in young care, have reproductive castes cared for by nonreproductive castes, and have overlapping generations where offspring assist parents.

Hymenoptera

The order of insects containing ants, bees, and wasps, which includes many eusocial species.

Diploid

Having two forms of chromosomes, with one inherited from the father and one from the mother.

Haploid

Having only one sex chromosome; in some social insects BEES, males are haploid because they develop from unfertilized eggs.

Haplodiploidy

The basis for eusociality in certain insects where females share $75$% of their genes with sisters, as 1 male mates with the quuen bee. Making them more related to each other than to their own mother ($50$%) or potential offspring ($50$%). They share 100% of genes with father.

Heterocephalus glaber

The scientific name for the naked mole rat, which is cited as the best example of a eusocial mammal.

Parent-offspring conflict

Conflict arising because parents share only $50$% of genes with each offspring and must divide investment among multiple young, while offspring want maximum time and energy from the parent. Can occur in utero → gestational diabetes

Sibling rivalry

Competition for resources like food or space among siblings who only share between $25$% and $50$% of their genes, sometimes resulting in larger siblings killing younger ones. Ex. pigs, hyenas.

Kin recognition

Vocal, visual, and chemical systems favored by evolution to help animals discriminate relatives from non-relatives, or the use of "rules-of-thumb" algorithms like helping those in your own nest.

maxes inclusive fitness bc not caring for non-relatives.