Aug 29, 2007, 9:54 GMT
Vienna - Men who select a partner six years younger will have more children, Austrian researchers said.
The same rule applied to women if they picked a man four years their senior, an Austrian study published in the British Royal Society's Biology Letters said.
Austrian researchers Martin Fieder and Susanne Huber of Vienna University tried to solve the riddle why men chased younger women, and why women were attracted to older men.
Anthropologists usually explain those patterns with a female's search for resources and status, more likely to be found in older men, while men are attracted by young, visibly fertile partners.
While those age preferences could be seen to be common sense and culturally universal, the study proved for the first time that it had effects on reproduction, Fieder told Deutsche Presse-Agentur dpa.
Couples with the optimum age difference produced an average of 2.2 children, compared with 2.1 if they chose a partner the same age, the study said. Fieder and Huber looked at data from 10,000 Swedish men and women who did not separate from their partners between the birth of their first and last child.
If the chosen partners were, however, significantly older or younger, the number of offspring diminished.
Another interesting outcome was that men and women who traded partners tended to chose for their second partner a person younger than the first partner.
'We expected this from men, as it is known that they choose a significantly younger second wife,' Fieder said.
That women showed the same tendency came as a surprise to the researchers.
'We think that women want to have children again with their second partner, which is more likely with a partner less old than their first,' Fieder said.
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