Science: The Truth About... Amber

AMBER HAS been admired for its golden hues since time immemorial. It is only in recent years, however, that the wider public has become aware of its unique fossil-preserving features, thanks to Hollywood's Jurassic Park, which depicted the fictional extraction of dinosaur DNA from a mosquito trapped and preserved in amber for millions of years.

The decorative qualities of amber have made it a sought-after substance since at least the Bronze Age. Scientists also look upon it as a source of information about the distant past. Although no one has so far extracted dinosaur DNA from an amber-trapped insect, biologists have nevertheless been able to discover intriguing insights into early evolutionary history as a result of studying the imprisoned and often extinct life forms trapped in the fossilised tree resin.

Certain trees exude sticky resin to protect their vulnerable bark against attack. The resin gums up the jaws of tree-eating insects and its antiseptic properties help to kill invading bacteria and fungi.

When bark exudes its resin the sticky blobs can engulf anything they land on, including insects, spiders, flowers, seeds and even small lizards. Its antiseptic nature and lack of water help to prevent the organisms from decaying straightaway. As the volatile components of the resin evaporate, the sticky exudate begins to amberise and dry out, enhancing its preservative qualities.

The organic molecules of the resin form bonds to make bigger molecules, in a process known as polymerisation, which is similar to the chemical reactions resulting in the formation of plastics. Hardened resin, known as copal, gets incorporated into soil and rock and remains around long after the tree dies. Amberisation - when fossilisation is complete - takes a further 2 to 10 million years. The result is a completely inert substance, which can survive intact for hundreds of millions of years.

Dominican amber is the best preservative. The extraction of DNA from amber-trapped insects was first reported in 1992, when scientists claimed to have recovered small stretches of genetic material from a bee in amber.

However, Andrew Ross, curator of fossil arthropods at the Natural History Museum in London, who has just published a booklet on amber, has failed to repeat the DNA-extraction experiments, which casts doubt on whether the DNA really was from an ancient insect, or whether it was the result of laboratory contamination.

As for the idea of ever extracting dinosaur DNA from a trapped mosquito, Dr Ross is even more sceptical. "Even if DNA could be extracted from insects in amber, a real-life Jurassic Park is not possible. There are many reasons why such a venture will remain fiction. First, there are no known insect- bearing Jurassic ambers. Second, contrary to popular belief, mosquitoes are extremely rare in amber."

Steven Spielberg, please note.

`Amber: The Natural Time Capsule', published by the Natural History Museum, pounds 7.95