Women's longevity may depend on the age at which they get pregnant, say Rudi Westendorp of the Netherlands and Thomas Kirkwood of the UK. Those who have their first pregnancy at a late age seem to live longer than those who bear children earlier, they add. The duo also says those who have fewer children seem to live longer. Westendorp and Kirkwood studied the British aristocracy's records since AD 740, which had entries of births, deaths and marriages of more than 33,000 people, including 13,776 women. The duo scrutinised the records of women who had lived longer than 60, and found that they had the fewest children and postponed the birth of their first child. Those who had the first child in their 40s had a great chance to become centenarians. Almost half the women who lived to the age 81 or older had no children at all. Evolutionary biologists speculate that the genes that promote fertility and a robust constitution in early adulthood also lead to more rapid ageing by leading to health problems such as cancer, Alzheimer's disease and heart ailments ( Nature , Vol 396, No 6713).