1 Puberty

2 “I think that what is happening to me is so wonderful and not only what can be seen on my body, but all that is taking place inside. I never discuss myself with anybody; that is why I have to talk to myself about them.” Anne Frank

3 Hormones & Puberty Hypothalamus stimulates pituitary gland –growth hormone  which causes growth spurt –ovaries and testes release gonadotrophins (sex hormones) males: testosterone females: estrogen and progesterone

4 Hormones & Puberty hormones stimulate –growth of primary sexual characteristics (genital) –growth of secondary sexual characteristics (non-genital) –precursors to adult sexuality

5 Sex Differences in Puberty Growth spurt begins –10.5 years in girls –12.5 years in boys –girls taller than boys between ages years full adult height –17 years old in girls –21 years old in boys

6 Sex Differences in Puberty Menarche: first menstrual cycle –typically occurs by age –initially may involve anovulatory, irregular cycles Spermarche: first ejaculation –typically occurs by age 15 –initial period of sterility

7 Sex Differences in Puberty Puberty marks an increased incidence of internalizing disorders in girls compared to boys (Haward & Sanborn, 2002; Kessler, 2003) Due to hormones? Environmental variables? Pregnancy? Is depression adaptive? (Nesse, 2000)

8 Precocious and Delayed Puberty Girls who enter puberty early more likely to have teen pregnancy girls who have teen pregnancy, more likely to have daughters with teen pregnancy

9 Precocious and Delayed Puberty Vandenbergh Effect –male present --> earlier onset of puberty –females only --> later onset of puberty –may be a way of regulating population density

10 Precocious and Delayed Puberty  Stable species – unchanging predictable environments, live long lives in large populations, large bodied, lavish lots of parental attention on few offspring – reach puberty later Opportunistic species – unstable unpredictable ecosystems – conditions good, everyone begins mating or pollinating --> conditions favorable, reach puberty rapidly

11 Precocious and Delayed Puberty Absent Father Theory: –girls abandoned by their father behave like females from opportunistic species and reach puberty earlier (Draper, Belsky, & Harpending). –process may be caused by pheromones

12 Precocious and Delayed Puberty Strategies for reproductive success 1) early pubertal development, low investment in offspring 2) later pubertal development, high investment in offspring (Belsky, Steinberg & Draper, 1991)

13 Precocious and Delayed Puberty Evidence in support: –females with absent father reached puberty earlier (Surbey, 1988, 1990) –females with greater emotional distance from parents reached puberty earlier (Sternberg, 1988) –females with greater stress in parental relationship reached puberty earlier (Surbey (1988, 1990)

14 Precocious and Delayed Puberty Correlation does not equal causation!!!

15 Precocious and Delayed Puberty Absent father predicts early puberty : –stress tends to delay menarche –postpuberty stress inhibits ovulation

16 Precocious and Delayed Puberty Absent father predicts early puberty –absent father may lead to lower SES –lower SES may lead to problems associated with early menarche

17 Precocious and Delayed Puberty Absent father predicts early puberty –Wamala et al. (1997) 300 Swedish women ages examined reproductive history, weight, SES Findings: SES and obesity associated with higher number of children and earlier menarche

18 Precocious and Delayed Puberty Absent father predicts early puberty –when the father is absent, mother may have poorer prenatal care (diet, rest, etc) –Koziel & Jankowska (2002) 1060 Polish girls aged 13.5 to 14.5 years collected BMI and weight data Findings: BMI and birthweight affected onset of menarche

19 Precocious and Delayed Puberty Early puberty predicts absent father: –Mother’s genetics predicts earlier puberty –Girls with early puberty get attention from males earlier - more likely to get pregnant? –Girls likely to inherit onset of puberty from mother

20 Precocious and Delayed Puberty Third variable predicts absent father and early puberty: –variant of x-linked androgen receptor that: predisposes father to unstable relationships causes early puberty in female offspring who inherit –Comings et al. (2002): significant association between this gene and the following characteristics : aggression and impulsivity increased number of sexual partners sexual compulsivity paternal divorce father absence early menarche in females

21 Precocious and Delayed Puberty Early puberty, early spermarche –Kim & Smith (1999) 509 students surveyed Finding: earlier spermarche associated with: –less emotional closeness with mother –earlier age of first intercourse –more girlfriends