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Puberty PowerPoint Presentation

Puberty

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Puberty

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  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 11-13 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 12-13 • 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 30-65 • 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