Patterns of Social Behavior

Sociability: an important primate characteristic

Advantages of Group Living

• 1. Makes possible observational learning.– Shortcut past individual trial-and-error

learning.• 2. Increases possibility of genetic resistance to

disease and parasites. • 3. Increases the fitness of group members.– Reproduction opportunities activities more

predictable– More efficient location of food resources.– Group defense

Grooming 1) prevents aggression; 2) maintains groupcohesiveness

An individual’s Inclusive fitness: direct + indirect components Direct: reproducing Indirect: assisting relatives in raising offspring

Reproductive strategies

• Female. • To maximize the amount of resources

available to her and her offspring.• Non-human female primates spend most

of their adult lives pregnant, lactating, or caring for offspring.

• Daily energy demands are as great as the larger males.

Female reproductive cycle

Signals of ovulation (vary)1. Morphological: perineal swelling and pigmentation (baboons & chimpanzees)2. Behavioral: females approach males and present

3. Pheromones = hormones that carry scent messages

Examples of social organization

Foraging units withinlarger groups

Single male harem: Gelada baboons

Lip retraction: threat display

Maintain exclusiveterritories

• Solitary• Males are intolerant of one another.• Single male establishes a large territory.• Contains several females• Each female has her own separate home range

• Polygany• Strongest bonds between male and his • females• All occupy an extensive range

Strongest bonds among males (hunting & defending sharedterritory Females not strongly bonded to other females or to any one male. Overlapping territories

Females sexually receptive less than 5% of her adult life.

• Peaceful• Strongest social bonds among females• Females also bond with males.• Status of male depends on social status of his mother.• Females sexually receptive for about 1/2 of her adult

life.

• Human societies extremely diverse • Monogamy, polygyny, and polyandry• For most of human evolution - and for most

women in the world today, menstruation is a rare occurrence

• Repetitive pregnancies and long periods of lactation

Grooming: systematically picking through the hair of another individual to remove foreign matter

Male strategies

• Produce many offspring and make sure they are yours

• Non-humans: androgen levels fluctuate in response to female receptivity.

• New dominant males may attempt infanticide. If infants are killed, females immediately go into estrus.

Nonhuman Cultural Behavior

• Cultural behavior is learned and passed from generation to generation

• Chimpanzees: tool use• Termite fishing with modified stems and twigs.• Have a preconceived idea of what the finished

tool needs to be in order to be useful.• May make the tool before a termite mound is

seen. • Preparing for the future. Requires planning and

forethought.

“The thinker”

Look familiar?