Rareness of Monogamy
- 90% of birds
- 3% of mammals
- 27% of primates
Cost and Benefits of Monogamy
benefit: co-parenting increases odds of offspring survival, female protection
cost: decreased opportunity to spread genetic material, challenges of mate-guarding
Reasons for Monogamy in Primates
- possibly for biparental care
- mate-guarding in males that increases confidence in offspring paternity
- risk of infanticide
Human Design for Monogamy
Testes Size: in primates there is increased sperm competition therefore men adapt
Evolutionary Adaptations:
- penis as a sperm displacement device
- increased sperm count in couples that spend less time together
Clues for Male Monogamy from Sexual Dimorphism
- fertile all the time
- in monogamous species males and females are more physically similar
- decreased competition between males for mates lessens the need for competitive features
pair-living
two adults and non-reproductive offspring sharing a home range, still with extra-pair mating
pair-bonding
long-term social relationship between two individuals
monogamy
mating and breeding system with sexual exclusivity
Prairie Voles and the Monogamous Brain
- higher release of oxytocin and vasopressin during mating, regulating pleasure centre of female brain, associating happy experience with vole they are with
- compared to Montane vole that show less activation of these hormones during sexual activity
