Why men like to marry younger women
By Roger Highfield, Science Editor
Last Updated: 12:01am GMT 05/12/2007
The reason that men like to marry women who are years younger than themselves has been discovered: they have more grandchildren as a result.
And it turns out that men have the most children when their partners are around 15 years their junior.
Michael Douglas, 63, married a much younger Cathering Zeta Jones, 38
There are many more well known "May to December" relationships such as Tony Curtis, 82, and Jill Vandenburg, 40, Des O'Connor, 75, and Jodie, 38, Michael Douglas, 63, and Catherine Zeta Jones, 38, or the late Anna Nicole Smith who married an ailing 89 year old oil tycoon when she was only 26.
Indeed, records show that most men marry younger women.
A study published today in the journal Biology Letters, provides evidence that the reason for these unions is that men prefer young women due to their high fertility while women prefer older men due to their wealth and high social status, which make them good providers for the offspring.
Although this idea has been around for a long time, few studies have been done to show that this is true and have demonstrated that more and healthier children are the result.
Now Dr Samuli Helle, University of Turku, has found the answer with the help of a study of the nomadic Sami, the "reindeer people" of Finland.
Finnish parish records from the 17th to 19th century on three Sami populations, who depended on reindeer herding, fishing and hunting for their livelihood, make it possible for researchers to disentangle the effects of medical progress on the number and life span of Sami men who married only once.
What they found was that the men maximized their "evolutionary fitness" - ability to pass on their genes to future generations - by marrying women who were 14.6 years younger, and vice versa.
"Those men had the highest number of offspring surviving to adulthood," said Dr Helle, who did his study with Drs Virpi Lummaa of the University of Sheffield and Jukka Jokela of the ETH in Zurich.
"Young Sami women were the most fertile and had the highest reproductive value, whereas older Sami men had acquired enough skills needed for successful hunting, fishing and reindeer herding and, most importantly, wealth to be good providers for the progeny and thus desirable mates," they conclude.
However, most couples failed to marry with this huge age difference, usually opting for a small difference, suggesting that there were social factors at work too, so that Sami society frowned as much on a big age difference as we do today.
Last week, Dr Helle reported another Sami study which showed that warm years skewed birth sex ratio towards males, so that one per cent more boys were born for each degree C rise the previous year.
Similar findings have been seen in Germany and, in the late 20th century Europe, more males we born in southern latitudes than in northern latitudes. But Dr Helle said the underlying reason and the mechanisms are not understood.
There are still around 75,000 Sami ("sapmelas" in Sami) and their homeland ("Sapmi" in Sami) reaches from Central Norway and Sweden through the northernmost part of Finland and into the Kola Peninsula.
