Evolutionary Psychology of the Family

Human babies are dependent on parents for a long time.
Newborns can only sleep and feed.
They depend on caregivers for food, warmth, and safety.
Similar to newborn chimpanzees and other primates, but different from other mammals where offspring are more independent.

Primates are born "prematurely" to safely pass through the birth canal.
Human babies have proportionally bigger heads.
Once the head passes through the vagina, the rest of the body follows l more easily.
If humans were born later, they would be too big for vaginal birth, risking injury or death to the mother.

Other great apes wait longer between births (around 5 years), balancing with their longer lifespans.
Humans have shorter birth intervals (1-2 years in modern humans; 4 years in pre-modern humans) despite living longer.
This is partly due to co-operative breeding practices (e.g., alloparents).
Short birth interval results in increased pressures:
- Lactation is highly calorific.
- Mothers carry infants and toddlers, which is difficult with multiple young children.
- Higher risk of still or premature birth with short inter-birth intervals.

How do we offset the costs of brain development with the benefits of brain development?

A part of evolutionary theory that accounts for trade-offs within the lifespan of individual organisms.
To maximize reproductive success, organisms must make compromises across several variables.
Life-history theory explains the existence of families across the animal kingdom.
Predicts that the longer an organism lives (as a species), the more likely family systems will evolve.

Fast life history:
- Resource unpredictability/abundance.
- Early onset of reproduction.
- Dispersal and family dissolution.
Slow life history:
- Delayed onset of reproduction.
- Parental investment.
- Retention of young and family formation.
Breeding conditions, offspring survival probability, and offspring age/experience influence the life history strategy.

In developmental psychology, attachment is a concept where:
- Children seek to be with a caregiver, especially during anxiety- or fear-provoked episodes.
- In the presence of a suitable and responsive caregiver, the child’s social and psychological development will be more successful than in the presence of an insensitive caregiver (or where no secure attachment has formed).
Proposed by Ainsworth and Bowlby, with evolution in mind.
Infants with secure attachment are more likely to grow up and successfully reproduce (Ultimate Cause).

Secure strategies (low risk):
- Favors future reproduction (delayed reproduction) and high parenting effort.
- Can be affected by factors like genetics, prenatal/perinatal hormones, environmental effects.
Anxious strategies.
Avoidant strategies (high risk):
- Favors current reproduction and high mating effort.

Even though most species do not form families, there are distinct advantages to living as a family unit.
Delaying reproduction and parental investment allows time for offspring to learn and develop useful skills:
- Education.
- Social rules.
- Practical skills.
Increased survival probability means that more offspring will go on to reproduce in turn – Ultimate Cause.

Costs to parents include:
- Biological costs: Production of gametes (especially for females), production of milk, energy spent in other child-rearing activities.
- Financial/Material costs: Housing, food, education.
- Personal costs: Physically protecting offspring from danger.
- Fitness costs: Time spent finding a suitable mate, time cannot easily be split raising different sets of offspring, risk of “investing” in raising a child that is not your own (for males).

Family members contribute in different ways:
Human babies require substantial investment and resources to raise, mostly by the mother.
Fathers contribute only ~5% to direct parental care, providing most care indirectly.
Human fathers contribute significantly more compared to other primate species, with modern trends pushing towards equal division of child care.

In chimpanzees, the polygynandrous mating system means males have no exclusive sexual relationships (females mate with multiple males).
Father-offspring recognition is non-existent in chimpanzees.
This leads to a diffusion of responsibility.

Alloparents are members of the group/family who are not the parents but contribute to the care and raising of offspring.

In primate species, alloparental care increases reproductive rates (i.e., shorter interbirth interval) and faster growth of offspring (i.e., faster weaning time).
Alloparents also act as a failsafe should one or both parents die, otherwise offspring would most likely not survive.

A table showing consanguineous marriage is observed in varying percentages around the world.

How to avoid inbreeding?
- Kin recognition
- Dispersal
- Familiarity
- Co-residence

Compare human development to that of other mammalian species.
Describe what a family is and why it would be selected for.
Understand attachment from an evolutionary point of view.
Explain how division of care in parental activities are beneficial to child survival.