Family values may have declined over the 20th century, but blood remains thicker than water 鈥� just about. That鈥檚 according to a comparison of childless couples in 1910 with those of today.
Thomas Pollet at the University of Newcastle, UK, and Robin Dunbar of the University of Oxford studied . They found that childless couples were three times as likely to have young nephews and nieces living with them as were couples with children. 鈥淭hese young children would be a biological cost,鈥� says Pollet, because they would need feeding and clothing.
The fact that couples did this is evidence that the 鈥渉elpers at the nest鈥� hypothesis 鈥� which says that family members will act to improve the reproductive success of others in their family 鈥� is active in humans, he says (Journal of Biosocial Science, ).
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鈥淭hese family ties are more difficult to detect in modern society,鈥� says Pollet. With the advent of contraceptives, couples can control the size of their family, so children are less likely to be passed on to childless siblings.
However, modern childless couples care for their nieces and nephews in other ways. 鈥淲e analysed Belgian families in 2004, and found that women are more likely to have had recent phone or email contact with nephews and nieces if they are childless themselves,鈥� says Pollet. He also says that statistics show an individual is more likely to lend money to a sibling with children. 鈥淏ut if your sibling is childless, you keep your money to yourself.鈥�
