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Lecture 7 primate behavior - reproduction and protoculture


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Lecture 7 Primate Behavior - Reproduction and Protoculture

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Lecture 7 primate behavior - reproduction and protoculture

  1. 1. Anthropology 101: Human Biological Evolution Lecture 7: Primate Reproduction and Protoculture
  2. 2. Behaviors are adaptations to particular social environments • Behavioral strategies • Course of action under certain circumstances • Does not imply conscious reasoning, deliberate planning, or intent • How does the behavior effect and individual’s fitness • Costs vs. Benefits of an action
  3. 3. Mammalian females are committed to invest in offspring • Internal gestation (pregnancy) • Lactation (nursing) • Maternal investment obligatory • Paternal care optional
  4. 4. Selection shapes reproductive strategies • Females: • Time & energy limits how often can have new infant (reproductive success) • Males: • Reproductive success limited by: • Number of mating opportunities • Access to females • Range of strategies that will affect male reproductive success • More options
  5. 5. 1. Males can increase RS by investing in offspring Expect males to invest when: 1. Finding additional mates difficult 2. Fitness of kids raised by just mom is low • infants are very big • litter size > 1 • high risk of predation/infanticide
  6. 6. 2. Males can increase RS by competing for mates • Sexual Selection favors traits that increase success in competition for mates • Competition may or may not = a fight! Two kinds of sexual selection: • Intra-sexual selection = male-male competition for access to mates • Inter-sexual selection = female selection of males with the most attractive traits
  7. 7. Intra-sexual selection in primate males • Male-male competition favors • Large body size • Large canines (NOT meat) • Mate guarding
  8. 8. Inter-sexual selection in primate males Inter-sexual selection = Female choice favors • Flashy colors • Energetic displays • Friendly behavior • Paternal care mandrill tamarin
  9. 9. Ex: Male Investment Pair-bonded species: Marmosets & Tamarins • Male RS tied to his mate’s RS • Males invest in offspring • Carry infants • Share food with infants • Males guard females vs. rivals • Closely bonded to mate Dusky titi monkeys
  10. 10. Ex: Male Investment Pair-bonede species: Gibbons and siamangs Males are attentive to mates Sing duets in territorial displays Females have priority of access Males help care for infants
  11. 11. Ex: Male Competition Fights & distant fathers: multi-male groups • Male RS tied to number of different females he can mate with • Males compete for dominance rank • Favors large size & strength • Favors large canines (NOT meat) • Rank orders change frequently • Male rank is correlated with reproductive success Chimps & Baboons
  12. 12. Ex: Competition & Investment In multi-male groups, some males provide low cost care • Males usually tolerant of juveniles • Males support juveniles in their fights • Males may selectively help own offspring
  13. 13. One-male groups: Competition to gain access to females is intensified • Males compete for access to group of females • Outsiders put high pressure on resident males • Tenure of resident males often short • VERY intense competition • May favor infanticide under very particular circumstances
  14. 14. Infanticide: sexually-selected male reproductive strategy • Females nurse infants for many months • If nursing infant dies, female resumes cycling immediately • female available for mating sooner • If male tenure as resident male is short: • infanticide enhances male mating opportunities
  15. 15. Circumstances of infanticide • Male takes over a one-male multi- female group or rises in rank • now has mating opportunities for a short time • Kill infants that are NOT their own • Kill very young infants still nursing • Male gets to mate with the dead infant’s mother
  16. 16. 0 10 20 30 40 50 Sifaka Howler Langur Blue Monkey Baboon Gorilla Chimp High Low %deathsduetoinfanticide Infanticide is a major cause of mortality
  17. 17. Counterstrategies to thwart infanticide • Defend victims of attack • Mothers • Female kin • Males present at conception • Fathers • Confuse paternity • Estrus swellings • Mate with many males • Mate with newcomers
  18. 18. In baboons, male-female ties may prevent infanticide • In some populations, infanticide is common when new males join group or males rise in status • New mothers form associations with particular males • possible father of current infant • Males protect females’ infants
  19. 19. Sexually-selected infanticide is widespread • All the major groups of primates • Prosimians • New World monkeys • Old World monkeys • Apes • Lions • Rodents • Birds Many still think its pathological and not adaptive
  20. 20. Controversy persists because people confuse what IS with idea of SHOULD or GOOD • This confusion is called the “naturalistic fallacy” • assumes that natural phenomena are right, just, unchangeable, good • Worry that if infanticide is adaptive for langurs or lions, it would be justified in humans • WRONG! • We can’t extract moral meaning from behavior of other animals or what is natural. • Culture and own choice determine right and wrong. Not nature.
  21. 21. The costs & benefits of social interactions: It takes two Actor’s Fitness Recipient’s Fitness Selfish + - Mutualistic + + Altruistic - + Spiteful - - cooperation easily explained by natural selection rare or absent in non-humans
  22. 22. For altruism to evolve, must limit altruism to other altruists • Kin Selection • Limit altruism to kin • Share genes so your genes benefit • Focus on close kin S. Alberts • Reciprocal Altruism • Limit altruism to those who help you • Alternate benefits with partner
  23. 23. How do we know who is kin? Mothers - Learn via close contact = familiarity - Learn about female kin via time with mom - Siblings, aunts, grandmother - Fathers?
  24. 24. Primates sometimes recognize paternal kin? - Males know they mated with mom - Males know who else mated with mom Reliability of “guess” varies • Pair-bonded species • One-male groups • Multi-male groups If one male does 100% of mating: = father of all kids conceived during his tenure = all kids born during his tenure will be paternal half siblings
  25. 25. Cooperation via Reciprocal Altruism • Individuals take turns giving and receiving benefits • Reciprocal altruism requires 1. Frequent opportunities to interact 2. Keep track of help given and received by specific individuals 3. Stop helping if don’t receive help in return  Don’t get cheated!!  Primates likely to meet requirements
  26. 26. Monkeys and apes have big & complex brains, particularly neocortex – why? galago rhesus chimpanzee -Cooperation -Learning -Complex behavior -Problem solving
  27. 27. Learning and problem solving evolved for ecological reasons: Ecological Intelligence Hypothesis Solving complex ecological problems • Processing inaccessible food items • Extractive Foraging • Locating and remembering food sources • Navigating between food sources • Cognitive Maps • Apes, Capuchins larger brains, more complex foraging • Many simple species make cognitive maps, navigate complex food sources • Butterflies, birds, Aye Ayes
  28. 28. Learning and problem solving evolved for social reasons: Social Intelligence Hypothesis • Solving complex social problems • Keeping track of kin • Keeping track of relative rank • Remembering benefits given & received • Manipulating rivals • Managing coalitions All the joys of living in a large group!
  29. 29. How do we define culture in humans? • Learned • Patterned • Nonrandom • Inter-related • Systematic • Transmittable • Learned • Stored • Accumulates • Are humans unique?
  30. 30. How do we define culture (protoculture?) among nonhuman primates? • Information acquired via social learning • Not a species typical behavior • Not genetically inherited • Presence/absence not only due to ecology • Different patterns of behavior in different groups
  31. 31. Culture, Behavioral Traditions, Protoculture • Potato washing in Japanese macaques • Chimps: • Ant fishing • nut cracking • Hand-clasp groom • Still, a large difference from humans • Single behaviors • Limited domains • Little accumulation