Diet and Body size
Only tiny primates rely on insects and/or gum
Small primates can eat fruit for carbohydrates, insects for protein
Medium-sized primates eat fruit for carbs and leaves for protein
Large primates can rely on abundant but nutrient poor plant foods
Morphological Correlates with Diet: Tooth and gut morphology varies with diet.
Frugivory (fruit): Large incisors, molars with low cusps, long small intestine
Folivory (leaves): Small incisors, shearing crests on teeth, big stomach/large intestine
Insect-eating: sharp, pointy cusps on teeth, simple gut
Proper Socialization starts with Mom
Harlows isolated infant monkeys from mothers
Deprived infants became poorly socialized adults, bad parents
Warmth, comfort, security important for normal development
Differing Reproductive Strategies of Males and Females Affects Sociality
Females always care for young
Males generally don’t
Why this difference in parental care?
Asymmetry in Reproductive Investment
Only females get pregnant and lactate
Birds: 90% monogamous
Mammals: 90% uneven investment
Pregnancy and lactation commit mammalian females to invest in their young
This process in and of itself limits the benefits of male investment in offspring
Males cannot lactate, can never raise young without females
Birds--each sex can equally care for the growing young
--90% of bird species are monogamous
What Determines Paternal Investment (CAD versus DAD)?
• Care by both parents will evolve when:
– Fitness of offspring raised by one parent is low
– Mates are hard to find
• Care by one parent (female) is likely when:
– Fitness of offspring raised by one parent is high
– Mates are easy to find
Why Do Many Primates Live in Groups?
• Enhanced access to resources
• Reduced vulnerability to predation
Costs of Sociality
Increased competition
Increased risk of disease
Increased exploitation by other group members
Benefits of Sociality
1
Only tiny primates rely on insects and/or gum
Small primates can eat fruit for carbohydrates, insects for protein
Medium-sized primates eat fruit for carbs and leaves for protein
Large primates can rely on abundant but nutrient poor plant foods
Morphological Correlates with Diet: Tooth and gut morphology varies with diet.
Frugivory (fruit): Large incisors, molars with low cusps, long small intestine
Folivory (leaves): Small incisors, shearing crests on teeth, big stomach/large intestine
Insect-eating: sharp, pointy cusps on teeth, simple gut
Proper Socialization starts with Mom
Harlows isolated infant monkeys from mothers
Deprived infants became poorly socialized adults, bad parents
Warmth, comfort, security important for normal development
Differing Reproductive Strategies of Males and Females Affects Sociality
Females always care for young
Males generally don’t
Why this difference in parental care?
Asymmetry in Reproductive Investment
Only females get pregnant and lactate
Birds: 90% monogamous
Mammals: 90% uneven investment
Pregnancy and lactation commit mammalian females to invest in their young
This process in and of itself limits the benefits of male investment in offspring
Males cannot lactate, can never raise young without females
Birds--each sex can equally care for the growing young
--90% of bird species are monogamous
What Determines Paternal Investment (CAD versus DAD)?
• Care by both parents will evolve when:
– Fitness of offspring raised by one parent is low
– Mates are hard to find
• Care by one parent (female) is likely when:
– Fitness of offspring raised by one parent is high
– Mates are easy to find
Why Do Many Primates Live in Groups?
• Enhanced access to resources
• Reduced vulnerability to predation
Costs of Sociality
Increased competition
Increased risk of disease
Increased exploitation by other group members
Benefits of Sociality
1
