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.

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Puberty

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“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

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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

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Hormones & Puberty

• hormones stimulate– growth of primary sexual characteristics (genital)

– growth of secondary sexual characteristics (non-genital)

– precursors to adult sexuality

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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

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• 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

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• 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)

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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

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• Vandenbergh Effect– male present --> earlier onset of puberty– females only --> later onset of puberty– may be a way of regulating population density

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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

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• 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

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• Strategies for reproductive success1) early pubertal development, low investment in offspring

2) later pubertal development, high investment in offspring

(Belsky, Steinberg & Draper, 1991)

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• 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)

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Correlation does not equal causation!!!

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• Absent father predicts early puberty:– stress tends to delay menarche

– postpuberty stress inhibits ovulation

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• Absent father predicts early puberty– absent father may lead to lower SES

– lower SES may lead to problems associated with early menarche

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• 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

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• 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

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• 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

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• 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

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• 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

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.

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