Bio Sisterhood: 25 flashcards

Kinship refers to the genetic relatedness between individuals, which can influence cooperative and altruistic behaviors among females.

Kin selection is an evolutionary strategy where individuals favor the reproductive success of their relatives, even at a cost to their own survival or reproduction.

Hamilton's rule states that altruism is favored when $rB > C$, where $r$ is genetic relatedness, $B$ is benefit to recipient, and $C$ is cost to actor. Sisters share high $r$, so altruism can evolve.

Reciprocal altruism is when individuals exchange acts of help over time, expecting future returns. It can stabilize cooperation among unrelated females.

The grandmother hypothesis proposes that menopause evolved because older females increase their inclusive fitness by helping care for grandchildren rather than continuing to reproduce.

Female philopatry is when females remain in their natal group. This keeps female relatives together, facilitating kin selection and cooperative behaviors.

Alloparenting is care for offspring by individuals other than the parents. Example: in elephants, older females (allomothers) help care for calves.

Cooperative breeding occurs when individuals help raise offspring that are not their own. In many species, females cooperate to feed and protect young, increasing group reproductive success.

Social grooming is cleaning and maintaining fur of others. It reinforces social bonds, reduces tension, and can be exchanged for support in conflicts.

Coalitions allow females to collectively defend resources, compete for dominance, or protect against harassment. They increase individual fitness through group support.

The tend-and-befriend response is a stress response more common in females, involving nurturing (tending) and seeking social support (befriending) rather than fight-or-flight.

Oxytocin is a neuropeptide that promotes trust, empathy, and bonding. It is released during childbirth, lactation, and social interactions, strengthening female bonds.

Inclusive fitness is an individual's total fitness, including direct reproduction and effects on relatives' reproduction. Sisterhood cooperation can increase inclusive fitness.

In baboons, females form strong coalitions to defend against harassment and improve access to resources. In bonobos, females cooperate to maintain social status.

A matrilineal society is one where descent and inheritance are traced through the female line. This often strengthens bonds among female relatives and promotes cooperation.

Females may compete for resources or mates but also cooperate when it increases inclusive fitness or group survival. The balance depends on ecological and social factors.

Social network theory examines how individuals are connected and how information, support, and resources flow through these connections. Female bonds often form dense, supportive networks.

A matriline is a line of descent traced through females within a single generation or family group, while a matrilineage is a longer, multi-generational female descent line. Both structure female cooperation in species like elephants and macaques.

Reproductive skew describes how reproduction is unequally distributed among group females. When skew is high, subordinate sisters may gain more by helping a dominant relative breed than by breeding themselves, favoring cooperative rather than competitive strategies.

MHC genes influence body odor and immune compatibility. Females can use MHC-linked cues to recognize close kin and avoid inbreeding, helping them direct cooperation toward relatives and choose compatible mates.

Older sisters often help raise younger siblings by providing childcare, food, or protection. This alloparental help increases the younger siblings' survival and lets the helper gain inclusive fitness benefits, especially when direct reproduction is delayed.

Reproductive suppression is the inhibition of ovulation or breeding in subordinate females, often caused by pheromonal or behavioral cues from a dominant female. In some cooperative breeders, sisters suppress their own reproduction to help raise the dominant's offspring.

Menopause may allow older females to redirect energy from their own reproduction to helping daughters, sisters, and nieces. This extended post-reproductive lifespan can strengthen female kin networks and increase the survival of related offspring.

The sister effect is the finding that women with sisters tend to have earlier menarche, earlier first births, and more children, possibly because sisters provide social support, information, and alloparental care that reduce the costs of reproduction.

Sisters compete for parental investment, status, and reproductive opportunities, but they also cooperate when shared genes make helping each other more beneficial than competing. The balance depends on ecological conditions, relatedness, and resource availability.