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Last Updated: Wednesday, 11 June, 2003, 07:47 GMT 08:47 UK
Peers give clues to human evolution
The family trees of aristocratic British families have offered insights into the way women unknowingly "traded" a long life for large numbers of children.

Lords, BBC
Their ancestors could help us unravel evolution
A study just published in a Royal Society journal is strong evidence to support the theory which says that women who have many offspring sacrifice longevity in the process.

Researchers believe that bearing children uses up valuable energy, which would otherwise be used to repair cells and slow down the ageing process - the so-called "disposable soma" theory.

Scientists, from the Max-Planck Institute in Germany, and the University of Cambridge, UK, used the Hollingsworth computerised genealogy, which carries the records of 30,000 peers and their families between 1603 and 1959.

The records of men and women who died after the age of 50 were analysed, to exclude women who died in childbirth.

Using a complex mathematical formula, the researchers worked to compensate for the fact that women who were naturally frail and unhealthy were less likely to have big families, rather than the other way around.

Higher risk

When all this was taken into account, the scientists found that early death was a third more likely among women who had eight or more children compared with those who had only two.

Baby
Having large numbers of children could extract a heavy price
Even women who had as many as four children had a reduced risk.

There was also an apparent disadvantage to having children early.

There was no discernable negative effect on men, regardless how many children they sired.

It is an evolutionary advantage for many organisms to favour reproduction over lifespan - they reproduce heavily, but, as a result, may not live as long.

This often applies to animals which are heavily predated - they need to reproduce as often as possible for their genes to stand a chance of survival.

Interestingly, studies have shown that when species with high reproductive rates and short lifespans are placed in an environment with no predators, their reproductive rates fall - and their natural lifespans extend.

More reliable

Scientists have looked for evidence of similar principles at work in humans, and the well-kept genealogies of the British aristocracy offer the best hope of finding them.

Jim Oeppen, from the University of Cambridge, and a co-author of the Royal Society paper, told BBC News Online that the study was the first to make the crucial compensation for the fact that healthier women naturally tended to be more fertile.

He said: "This means that the data is more reliable - and may explain the fact that other studies have shown contrasting results.

"It supports the theory that if you devote energy to child-bearing, you damage the future of your own body."

He said that another plausible explanation was that women with a stronger immune system might find it more difficult to conceive - but be better protected against infections.




SEE ALSO:
Test to predict longevity
31 Jan 03  |  Health
Ageing process 'key' pinpointed
31 Dec 02  |  Health
Breed early, die young
24 Dec 98  |  Science/Nature


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