Scientists have for the first time managed to retrieve an intact protein from a fossil bone more than 55,000 years old.

The research has the potential to be applied to much older fossils

Christina Nielsen-Marsh

The molecule was extracted from extinct bison remains dug out of the permafrost of Siberia.

The technique - if its sensitivity can be improved and extended to a range of different proteins - could provide a new tool to investigate the evolution of ancient animals, and even human ancestors.

The protein retrieved from the Bison priscus specimen was osteocalcin. It is a molecule involved in bone formation.

The research, carried out by scientists in the UK and the US, is published in the journal Geology.

Life errors

Scientists have traditionally used morphology - the comparison of shape and size of different bones - to try to understand how species are related to each other and how they have evolved over time.

DNA, proteins and evolution

The genes in our DNA are templates for making proteins Genes "list" the amino acids that cells use to construct proteins Proteins are large molecules that build and maintain an organism's body Read in reverse, a protein therefore gives you the DNA sequence from which it came Studying that sequence could yield information on how that organism has changed over time

Advances in molecular biology have now made these judgements more precise by allowing researchers to look directly at the differences in organisms' DNA, the genetic code that ties all life together.

Looking for mutations, or errors, in the DNA, for example, can give an idea of when species diverged and followed different evolutionary paths.

This type of information is relatively easy to get from living animals but is much more difficult to obtain from dead and extinct specimens as the molecules that made up their tissues rapidly degrade over time.

Nevertheless, scientists have made remarkable insights by mining useable fragments of DNA from creatures that died thousands of years ago - and now Christina Nielsen-Marsh, of Newcastle University, and colleagues have managed to obtain the complete sequence of a osteocalcin molecule from an Ice Age bison.

Hi-tech tools

What excites scientists is that proteins are more robust and likely to be longer lasting than DNA.

Calculations suggest that DNA may only survive for perhaps no more than a million years at most, whereas some proteins could possibly survive for up to10 million.

"We're still at the beginning stages; what we have done is very much proof of principle," Dr Nielsen-Marsh told BBC News Online.

"The research has the potential to be applied to much older fossils and extend our knowledge about the genetic make-up of ancient species further back into geological time."

The traces of protein being sought in the specimens are fantastically small. The US/UK team used an array of hi-tech laboratory tools including a development of the mass spectrometry technology that won this year's chemistry Nobel to find the osteocalcin in their bison bones.

"I can see this protein technique being used as another line of evidence with the DNA, as well as maybe being used in environments where the DNA doesn't survive as well.

"Now that we have the technique we can start looking for other proteins."

Really useful

The trick for researchers will be finding the more interesting proteins that hold really useful information about an animal's evolutionary history.

"The problem we have is that many of the common, structural proteins we find in bones - and with fossils that's all you have - don't have a lot of what we call phylogenetic information," co-researcher Professor Alan Cooper, of Oxford University, told BBC News Online.

"The sequence of amino acids from which these proteins are built tend to be the same again and again. But this latest work is a first step and if the sensitivity of the technology picks up we may be able to find the more interesting molecules.

"Remember, though, the proteins represent only a distilled version of the DNA and even if we could get all the proteins we wanted, we'd still be missing a lot of the really useful information.

"That's why getting at the raw DNA is still the best way. Currently, we can go back about over 100,000 years but I think the limit is going to be about a million years."