A small section of genetic code may hold an ageing key
Researchers from four US research centres, believe they have identified a particular part of the human genetic code which could play an important role in how well we age.
They looked at the entire genetic structure of 308 siblings who had lived to at least 90 - one of them had to have lived to at least 98.
They found that many had inherited a particular collection of genes, on their fourth chromosome.
Although there are hundreds of genes in the region they have identified, the scientists are now working to narrow down the candidates.
Their discovery is documented in the journal The Proceedings of the National Academy of Sciences.
Not simply chance
Professor Louis Kunkel, who led the study team, said that it was 95% likely that so many of their siblings sharing these was not simply an accident of chance.
He said: "It is clear to us that longevity has a genetic component.
"Frequently if there is one sibling who has lived to be 100, there will be a second or third sibling who also will live to be 100."
While these older siblings had probably inherited genes which expanded their natural lifespan, what set them apart from many others, he said, was their good fortune to avoid having genes linked to killer diseases such as heart disease, stroke, cancer and Alzheimer's.
Challenge ahead
Now, he says, the hard work really begins.
"We must try to find the gene in this region of chromosome four that confers the longevity.
"This is an extremely complicated process because there are as many as 500 genes in this region."
No-one has yet attempted to alter the lifespan of humans by genetic modification - although there are hopes that alterations to just a few genes might be enough to make a difference.
Certainly, it is the case that in so-called "lower organisms", like nematode worms and fruit flies, this can be achieved.