The burden falls on the only child or the one willing to take responsibility.

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Then later on it was one child only.

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Gordon Bell is not only one of the chief researchers on the MyLifeBits project, but also its poster child, having spent the last seven years digitizing a lifetime's worth of information.

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Once factors such as spinsterhood and early hysterectomy were eliminated from the statistics, it became clear that the centenarians were three times more likely to have given birth to at least one child in their 40s than those who had then gone on to live only an average lifespan.

ECONOMIST: Ageing