Puberty
“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
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
• hormones stimulate
– growth of primary sexual characteristics (genital)
– growth of secondary sexual characteristics (non-genital)
– precursors to adult sexuality
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
• 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)
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
 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
• Strategies for reproductive success
1) early pubertal development, low investment in offspring
2) later pubertal development, high investment in offspring
(Belsky, Steinberg & Draper, 1991)
• 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)
Correlation does not equal causation!!!
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Absent father predicts early puberty:
– stress tends to delay menarche
– postpuberty stress inhibits ovulation
• Absent father predicts early puberty
– absent father may lead to lower SES
– lower SES may lead to problems associated with early menarche
• 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
• Third variable predicts absent father and early puberty:
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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
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