L9 - Dispersal

Question 1

Dispersal

Answer 1

• departure from existing population or natal group
• typically one way
• away from siblings/parents

Question 2

Migration

Answer 2

• relocation on greater than normal scale, seasonal to/fro movement of populations between regions
• typically round-trip

Question 3

Ultimate benefits of dispersal

Answer 3

1. incest avoidance
2. find mates
3. find resources
4. reduced competition with kin
5. avoid predators/pathogens/parasites

Question 4

Costs of Dispersal

Answer 4

1. energetic costs of movement
2. mortality due to predation
3. time loss (trade-off with reproduction)
4. risk not finding good habitat
5. loss of kin (helping, being helped)
6. loss familiarity with environment

Question 5

Dispersal differences between males and females

Answer 5

1. Females food limited, males mate limited

2. Males usually disperse in polygynous species, females or both sexes disperse in monogamous species

Question 6

Philopatry

Answer 6

tendency of organism to remain in or return to area of its birth

Question 7

Male philopatric

Answer 7

tendency for males to remain in natal area (female dispersal)

Question 8

Female philopatric

Answer 8

tendency for females to remain in natal area (male dispersal)

Question 9

Facultative dispersal

Answer 9

• sometimes individuals will deviate from species-specific patterns –> depends on environment
• ex: sometimes almost 50% female chimps will remain with natal group when alternatives are limited
• ex: marmosets stay and help raise siblings when alternative opportunities are low

Question 10

Patrilocal

Answer 10

marriage pattern in which the couple settles in the husband’s community

Question 11

Matrilocal

Answer 11

marriage pattern in which the couple settles in the wife’s community

Question 12

Bilineal

Answer 12

• tracing kin through both parents

- involves inheritance of property, names, rights

Question 13

Patrilocal-patrilineal band model

Answer 13

• females disperse
• patrilineal/patrilocal bonds necessary for cooperative hunting
• males defend territory against other groups
• but the book Man the Hunter provides evidence of flexible patterns among H-G
• non-foragers tend to be more patrilocal than foragers

Question 14

Helm’s Measure

Answer 14

male primary kin divided by #male + female primary kin

Question 15

Human dispersal:

Foragers vs. farmers

Answer 15

• Horticulturalists are also multilocal
• also more matrilocal than foragers
• less brother-bias

Question 16

Human dispersal:

Foragers vs. pastoralists

Answer 16

• pastoralists are much more patrilocal (87%)
• high wealth inequality
• inherited wealth

Question 17

Ecological correlates of dispersal

Answer 17

• women have higher dispersal rates
• dispersal most likely at reproductive age
• people born into larger families (particularly younger siblings) more likely to disperse
• childless women more likely to disperse
• dispersal linked to timing of marriage
• inheriting sons less likely to disperse
• poorer people more likely to disperse
• sons with more brothers ore likely to leave –> sibling competition drives dispersal