An individual's DNA can help predict how long they will live early on in life, new research suggests.
Scientists studying zebra finches found the best indicator of longevity came from examining a piece of DNA called a telomere when the birds were 25 days old.
Telomeres occur at the ends of the chromosomes, which contain an individual's genetic code.
They are caps on the end of chromosomes that protect them from damage and function a bit like the plastic caps at the end of shoelaces.
This method of DNA protection is the same for most animals and plants, including humans, and the eventual loss of the telomere cap is known to cause cells to malfunction.
For the first time, scientists have now measured telomere length in the same individuals throughout their life span from early life onwards.
Researchers, led by a team at the University of Glasgow, studied 99 zebra finches whose lifespan ranged from 210 days to almost nine years.
They took blood samples at intervals to measure telomere length.
The scientists found that the best predictor of longevity was telomere length at 25 days.
It is known that the variation in telomere length is partly inherited, but also varies due to differences in environmental factors such as exposure to stress.
Professor Pat Monaghan, who led the team, said: "Our study shows the great importance of processes acting early in life.
"We now need to know more about how early life conditions can influence the pattern of telomere loss and the relative importance of inherited and environmental factors. This is the main focus of our current research."
The study was published yesterday in the Proceedings of the National Academy of Sciences USA.
The work was funded by the European Research Council, with additional support from the UK Natural Environment Research Council, the Wellcome Trust and the US National Science Foundation.