Girls are hitting puberty earlier and earlier. One recent study found that more than 10 percent of American girls have some breast development by age 7. This news has upset many people, but it may make evolutionary sense in some cases for girls to develop faster, according to the authors of a new paper published in Psychological Science, a journal of the Association for Psychological Science.
Girls who physically mature earlier tend to start dating, have sexual intercourse at a younger age, and have more sexual partners than girls who develop later. That puts them at risk of sexually transmitted diseases and makes them more likely to have a child while they're still teenagers. These are generally seen as bad things, says Jay Belsky, of Birkbeck University in London, given that many psychologists and doctors think there are right and wrong ways to develop. But he says it makes more sense to look at development the way nature doesfrom an evolutionary perspective. This leads to the expectation that growing up in a risky, unstable environmentthe kind that fosters an insecure rather than secure attachment of infant to mothershould accelerate pubertal maturation thus increasing the chances that one could reproduce before they die.
To test the relationship between a risky, unstable environment, as reflected in an insecure infant-mother attachment bond, and early puberty, Belsky and his colleagues used data on 373 white females from a large study of early child development sponsored by the National Institute of Child Health and Human Development. Girls in the study were followed from birth until the age of 15. At 15 months, security of attachment to mother was evaluated using a standard procedure involving separating and reuniting the baby with her mother in a university laboratory. Babies who smiled, vocalized, reached, or otherwise demonstrated appreciation that their mother was back were considered to be secure; those who avoided their mot
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Association for Psychological Science