For many parents of early-developing girls, “normal” is a crazy-making word, especially when uttered by a doctor; it implies that the patient, or patient’s mother, should quit being neurotic and accept that not much can be done. Allomong listened intently. He nodded and took notes, asking Tracee detailed questions about her birth-control history and validating her worst fears by mentioning the “extremely high levels” of estrogen-mimicking chemicals in the food and water supply. After about 20 minutes he asked Ainsley to lie on a table. There he performed a lengthy physical exam that involved testing the strength in Ainsley’s arms and legs while she held small glass vials filled with compounds like cortisol, estrogen and sugar. (Kinesiologists believe that weak muscles indicate illness, and that a patient’s muscles will test as weaker when he or she is holding a substance that contributes to health problems.)

Finally, he asked Ainsley to sit up. “It doesn’t test like it’s her own estrogens,” Allomong reported to Tracee, meaning he didn’t think Ainsley’s ovaries were producing too many hormones on their own. “I think it’s xeno-estrogens, from the environment,” he explained. “And I think it’s stress and insulin and sugar.”…

In the late 1980s, Marcia Herman-Giddens, then a physician’s associate in the pediatric department of the Duke University Medical Center, started noticing that an awful lot of 8- and 9-year-olds in her clinic had sprouted pubic hair and breasts. The medical wisdom, at that time, based on a landmark 1960 study of institutionalized British children, was that puberty began, on average, for girls at age 11. But that was not what Herman-Giddens was seeing. So she started collecting data, eventually leading a study with the American Academy of Pediatrics that sampled 17,000 girls, finding that among white girls, the average age of breast budding was 9.96. Among black girls, it was 8.87.

When Herman-Giddens published these numbers, in 1997 in Pediatrics, she set off a social and endocrinological firestorm. “I had no idea it would be so huge,” Herman-Giddens told me recently. “The Lolita syndrome” — the prurient fascination with the sexuality of young girls — “created a lot of emotional interest. As a feminist, I wish it didn’t.” Along with medical professionals, mothers, worried about their daughters, flocked to Herman-Giddens’s slide shows, gasping as she flashed images of possible culprits: obesity, processed foods, plastics.