Puberty

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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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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 --gt earlier onset of puberty
• females only --gt 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 --gt 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
• Mothers 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
• 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