Parental Investment in Modern Societies
Parental
care = any
form of parental behavior that appears likely to increase fitness of parent’s
offspring, e.g. care of fetus inside the body, provisioning young, financing
education, time spent in homework.
depreciable care = benefits of parental
expenditure decline with number of offspring, e.g. provisioning food
non-depreciable = benefits do not decline
with offspring number, e.g. parental vigilance, establishing a territory
Parental
investment = parental care that reduces
parent’s residual reproductive value. i.e. it is parental care that increases
offspring fitness at a cost to the parent. refers usually to investment in
individual offspring, while parental
effort is the sum investments in all offspring.
Among
vertebrates, biparental care in over 90% of 9000+ bird species; found in all
monogamous birds with altricial young; care is not necessarily shared equally
% male care in 53 mammal species
time parents spend talking with children under 5
years of age
Male
care in humans?
What
affects whether or not males help? They
are faced with the decision to either desert or stay.
When
benefits are too low or (opportunity) costs of parenting too high, males will
desert:
In birds where male care is little or none, offspring are precocious (develop quickly), terrestrial breeders (easier to hide nests from predators), or have a polygynous mating system.
Parental
effort is just one avenue of increasing fitness. Must consider opportunity
costs of parenting due to potential payoffs from increased mating effort.
Conflicts of interest.
1)
Parent-offspring
conflict. Trivers
1974 - figure 1, figure 2
conflict most intense when:
genetic
relatedness between siblings is low
costs of
offspring extortion are low
examples: weaning conflict,
psychological manipulation by offspring – crying
(“regress under stress”), temper tantrums
(threatening self-damage in chimps, pelicans, humans), parental rules and
discipline, role reversal in adolescence vs. becoming an adult
2)
sibling
conflict. differential investment in males/females by “quality”, or the
expected returns from each sex
% calories contributed by men and juvenile sex
ratio
3)
Between
spouses over desired levels of male and female parenting effort.
Sexual
division of labor. Complementary sex roles vs. substitutable sex roles
Cross-cultural differences in desired family size
Mean family size preference and disparity by sex
Classifications of male parental care
Father’s relevance to educational capital investment
in kids conceptual model
Relationship
to offspring and parental support for higher education
among
Albuquerque men sample - 1, 2, 3, 4
Capetown,
South Africa sample by Anderson et al.
There was an urban relocation of traditionally pastoralist
Xhosa in mid 20th century
I.D. Mkize Secondary School (worst high school in
Capetown due to poverty, inequality, gang presence).
Only 78% pass 8th grade, and 26% pass 12th
grade in this school.
Fees are about 50 rands ($10) per year at ID, compared
to 5000 rands at better schools.
n=603 students, or 89% of enrolled students
Time interactions with kids among Xhosa men
Financial expenditures on kids among Xhosa men
Distribution of students by grade
Distribution of years behind by grade
