10 10 family formation and reproduction Great Ape Mating Systems orangutan Male has bunch of females Gorilla single male multiple female chimp multi male and female society female mates with every male Humans multiple male and female we pair off 1 male to 1 female unique among mammals Marriage in humans mutually maintained long term reproductive relationship socially acknowledged sexual regulations high level of economic cooperation traditional explanation marriage facilitates the delivery of bi parental care sexual regulation offer paternity certainty division of labor more efficient Direct Paternal Investment in Mammals 5 among mammals 40 of primate genera exhibit direct care Callitrichids owl monkey What factors lead men to enjoy greater returns from parental investment Paternal Provisioning Model Altriciality helpless newborns prolonged development economic dependence Progency size Complementarity Mutually prohibitive tasks Specialization Marital Arrangements monogamy 1 female 1 male most common marriage worldwide limitations may lead to mistresses serial monogamy Increasingly more common as countries become industrialized Polygyny pural marriage Previous king of Bhutan and his 4 wives Practiced in 80 of population most families still monogamous though Sororal polygyny very common Associated with variance in men s value as husbands Polyandry multi male 1 female Best known example is in tibet fraternal most common associated with heritable land in tibet Getting Married Marriage often marked by elaborate ceremony Family involvement Marriage often marked by elaborate ceremony not always Family involvement Bride wealth exchange of wealth from groom s family to bride s family Bride Payment Bride Service Dowry exchangement of wealth from bride s family to COUPLE Divorce Widowhood great variance in perception of divorce and rates possibly linked to importance of fathers Remarriage following divorce or death also variable Levirate Pratice of marrying brother of deceased husband other cultures demand waiting period Nosuo Na China 40 000 people martial linage society stay with maternal family Walking Marriage couples initiate relationship under mutual attraction individual live with parents siblings Women s partners come to their bedrooms at night fathers have limited roles maternal uncles very important Women can have numerous partners rare Ache Familes lifetime number of husbands highest in subsistent population Survival of marriage very low Marriages Informal autonomy of couples to decide very little polygyny and polyandry first marriage age 15 women age 20 men average duration of 1 All end in divorce Reproduction mean age 19 women high fertility rate TFR 8 Many caretakers 80 of last births for mother also last birth for father