L11 - Birth Order Biased PI

Question 1

Social birth order

Answer 1

• number of older siblings dependent on same parents

- i.e. co-resident and living older siblings

Question 2

Biological birth order

Answer 2

-number of genetic siblings, regardless of survival status/residence

Question 3

Primiparous

Answer 3

mother at first pregnancy/birth

Question 4

Multiparous

Answer 4

-mother at any later pregnancy/birth

Question 5

Why do parents have higher fitness returns if they invest more in early born offspring?

Answer 5

1. they are more likely to survive to adulthood since they’ve already survive critical period when mortality is highest
2. likely to start producing earlier, shortening generation time
   - prediction: early born offspring should get more parental investment and do better

Question 6

Why are first borns disadvantaged in terms of birth weight and infant survival?

Answer 6

-physiological changes associated with fetal blood supply improve maternal environment for younger siblings

Question 7

Ultimogeniture

Answer 7

• preferential inheritance to laterborn offspring
• found in some land-limited agrarian populations
• may ensure lineage survival by reducing inheritance divisions over time, especially in face of harsh economic constraints such as habitat saturation

Question 8

Alfred Adler

Answer 8

-argued that birth order shaped personality

Question 9

Frank J. Sulloway

Answer 9

• wrote book Born to Rebel
• observed that sibling personalities often highly divergent despite shared genes and environment
• argued birth order creates distinct family niches and personality differences adapt accordingly
• but findings were criticized; failed to replicate results, cherry-picked examples, confounding variables