European researchers, drawing on 12 centuries of genealogical records of the British aristocracy, have shown a clear trade-off between early childbearing and longevity. In an article published last December in Nature, two gerontologists at the University of Manchester found that women who delay having children until their 30s and 40s, and then have only one or two, are more likely to live into their 80s, 90s and beyond. Female longevity, they say, is linked to the number of children a woman has and her age at the birth of her first child. This study comes in the wake of another carried out in the Boston area by a team of Harvard researchers led by Thomas T. Perls. It showed that centenarians are four times more likely than the general population to have had their first child in their 40s.