Article summary with Evolutionary context of human development: The cooperative breeding model by Hrdy - 2007

What is the environment of evolutionary adaptedness?

The environment of evolutionary adaptedness (EEA) is the ancestral environment to which a species is adapted. It is the set of selection pressures that shaped an adaptation. For a long time scientists (such as John Bowlby) believed that the standard EEA was characterized by mother-father child rearing, where the mother was the primary and exclusive caretaker.

What is cooperative breeding?

Cooperative breeding refers to a breeding system in which group members, other than the genetic parents, help one or both parents rear their offspring. The parental care provided by group members other than the genetic mother is called allomothering. Allomothers are individuals of either sex who are not the mother and can be male, and even the genetic father.

How does Hamilton’s rule explain the altruism of alloparents?

Hamilton’s rule states that the cost of helping should be less than benefits to offspring calibrated in line with the alloparent’s degree of relatedness to his or her charge. Alloparents enhance their inclusive fitness by helping kin. Allomothers help infants as long as cost is not prohibitive and so long as it does not interfere with their own future reproductive career or caring for their own offspring when they have them.

How can cooperative breeding be characterized?

Cooperative breeding systems are flexible and dynamic. They often have one or more mated pairs. There is delayed dispersal by maturing family members. There has to be sufficient phenotypic flexibility so individuals can shift between non-reproductive and reproductive roles. There has to be some underlying neural circuitry among alloparents to respond to signs of infant need.

How can cooperative breeding lead to slower maturation?

As a result of the help of alloparents, the usual quantity versus quality tradeoffs that constrain maternal decisions no longer pertain. Mothers can produce more (or more closely spaced) offspring because the total cost of rearing each offspring to independence can go up without jeopardizing the mother’s own survival or that of her offspring. Also, the reduced costs of child rearing and the benefits of group membership mean higher rates of maternal survival.

How does cooperative breeding influence emotional and cognitive development of infants?

Unlike most other primates, human mothers’ commitment is highly contingent on social circumstances. They respond to lack of support by failing to commit right after birth, abandoning the newborn, or infanticide. They also discriminate about which infants they invest in based on their sex, birth order, and viability. Babies that are born full term and healthy looking, that are sensitive to social support cues, and engage their mothers right from birth have a higher chance of maternal commitment. This supports their emotional and cognitive development.

Why are humans so cooperative and hyper-social?

Humans are distinguished from other apes by their cooperative heritage, instead of the usual competitive heritage. Infants born in cooperative breeding systems depend on different caretakers. Maternal commitment is contingent on the mother’s perception of support from allomothers. Infants have to be adept at monitoring caretakers, reading their intentions and moods, and eliciting their care. Through practice and conditional rewards, infants improve these skills and as they grow up and become adults, become members of a hyper-social, information-sharing, and culture-transmitting species.