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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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
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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)
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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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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
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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
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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
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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)
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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)
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Precocious and Delayed Puberty
Correlation does not equal causation!!!
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Precocious and Delayed Puberty
• Absent father predicts early puberty:
– stress tends to delay menarche
– postpuberty stress inhibits ovulation
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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
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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
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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
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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
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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:
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aggression and impulsivity
increased number of sexual partners
sexual compulsivity
paternal divorce
father absence
early menarche in females
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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
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