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 group cohesiveness

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 within larger groups

Single male harem: Gelada baboons

Lip retraction: threat display

Maintain exclusive territories

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 shared territory 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?