Girls beginning puberty earlier

• Girls in America are beginning puberty around 1 year earlier than 1970s
• Measured by development of breast tissue
• Average age of onset between 9.8 and 10.8 years in Europe, compared with 10.1 to 13.2 years in Africa and 8.8 to 10.3 years in the US
• Speculation that it may be related to BMI or environmental chemicals
• Scientists have no clue what it means or what causes it

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