Human Growth and Development / Unit 9 HGD 1226 short lesson, about 20 seconds
The Secular Trend
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The idea
The secular trend is a long-term change across generations; in the United States and Europe, average menarche fell from about sixteen a century ago to around thirteen.
In practice
Better nutrition, the likely main cause, with higher-income girls reaching menarche earlier in the Philippines and Nigeria.
Where people slip
The misconception is that puberty keeps getting earlier indefinitely; the trend levelled off from the nineteen sixties.
Your place on the trail
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