LIFE may have emerged from Earth's primordial slime millions of years before scientists thought it did, a team of international researchers reports.
They say they have found evidence that bacteria or something equally tiny lived in what is now Greenland 3.8 billion years ago not very long after the planet became fit for life.
The earliest known fossils - microscopic holes in ancient sedimentary rocks that used to be bacteria - are 3.5 billion years old.
Anything older would have been subjected to tremendous stresses as the Earth's crust shifted, so scientists looking for clues to the origin of life have to find chemical traces inside tiny pieces of hard minerals that could resist obliteration.
Dr Gustaf Arrhenius of the Scripps Institute of Oceanography in La Jolla, California, and colleagues in Britain and Australia say they found traces of carbon in apatite crystals that seem to have been formed by biological processes.
Using biochemical analysis techniques similar to those used by scientists who found evidence of life on Mars, Dr Arrhenius's group says the crystals contained carbon of a type that, as far as scientists know, is only created by living organisms.
They conclude, in a report in the science journal, Nature, that the isotopic results give strong evidence for life on Earth by 3.85 billion years ago.
Although this finding pushed back the horizon for the emergence of life by 300 to 400 million years, it is not entirely unexpected, given also the apparently evolved nature of lifeforms at 3.5 billion years ago, they write.
The problem is, they add, that scientists believe that just a few million years before the Earth was hit by a bombardment of meteorites so severe that it should have sterilised the planet.
"The evidence for life presented here overlaps this critical time period," they point out. But, if they are right, then the meteorite bombardment didn't wipe out all traces of early life and did not disturb the Greenland sediments.
. New research suggests a link between small size and long life expectancy. Scientists led by Ms Holly Brown Borg from North Dakota University, Grand Forks, have found that dwarf mice with a hormone deficiency live up to twice as long as their regular sized brothers and sisters.
The key appears to be lack of growth hormone. In other studies mice with too much hormone have had their lifespan reduced by premature ageing. Restricting calorie intake has also been found to extend lifespan in rodents.