BY BEN GILLILAND
|It is well known how a fossil forms. When an animal dies, the soft squidgy
bits - such as flesh, muscle and skin - decay and disappear, while the hard
bits, such as bone, are gradually replaced by minerals, leaving behind a
rocky cast of the original bone. However, even for something as hard-wearing
as bone, fossilisation is relatively rare. It takes the right combination
of circumstance and conditions for bones to fossilise and most simply rot
away over tens or hundreds of years. As such, it has long been accepted that,
under no circumstances, can squidgy bits survive for more than a few thousand
years - and even then they would need to have been frozen during the last
It therefore came as a bit of a surprise when Mary Schweitzer, an American palaeontologist, announced in 2004 that she had extracted some squidgy bits from a 68 milllion-year-old Tyrannosaurus rex fossil discovered in Montana. In fact, in palacontology circles at least, it was only slighfly less surprising than if someone had announced finding a 68million-year-old Boeing - 747 complete with dino-pilot. The sample, recovered from the femur (upper leg bone) of a female T. rex, contained blood cells, growth cells and connective tissue. It immediately prompted speculation that, in a sort of Jurassic Park scenario, it may be possible to extract dinosaur DNA.
However, since DNA is notoriously fragile and easily corrupted, Schweitzer concentrated on searching the sample for proteins, such as collagen, elastin and haemoglobin, which are slightly more robust and less sensitive to external contamination. Because proteins are a structural component in every part of the body, identifying them could provide a deeper insight into how a dinosaur's body functioned. And because proteins change through evolution, they could help us understand what dinosaurs evolved from and, possibly, what they evolved into.
Today, in the journal Science, Schweitzer announces that she has succeeded in identifying one of these proteins. She found that when she introduced collagen antibodies, taken from a chicken, to the T. rex sample, they reacted with each other. This suggested that not only was collagen 1 (the main organic component of bone) present, but that it must be similar to chicken collagen - implying that there is an evolutionary link between birds and T. rex. She then tested the collagen 1 protein fragments using a technique called mass spectroscopy,which essentially blitzes a sample into its component molecules to determine its chemical make-up.By comparing this sequence of chemicals with sequeneces taken from animals alive today she confirmed that the T. rex sample was most similar to bird collagen - in fact there was a 57 per cent match. The research has not only proven that, in the right circumstances, squidgy bits can be preserved for millions of years, but also adds weight to the idea that the scaly behemoths of the ancient past evolved into to the feathery fliers that poo on you car 30 seconds after you wash it.
Evolution down to warmer Earth
BY STEPHEN DEAL
PREHISTORIC global warming was responsible for the fast evolution of man's ancestors, not the decline of the dinosaurs, it was claimed yesterday. Most palaeontologists believe a massive asteroid strike 65million years ago killed off the dinosaurs, allowing mammals to flourish and begin evolving into today's current species, including humans. But an international team of researchers charting the evolution of all 4,500 mammalian species on Earth believes that present-day animals did not rise to prominence until ten to 15 million years after the dinosaurs died - around the time of a sudden increase in temperature. Prof Andy Purvis, of Imperial College London, said: 'It looks like a later bout of "global warming" may have kick-started today's diversity, not the death of the dinosaurs.' Scientists spent more than a decade studying the fossil record and using molecular analsyes to create their 'tree of life'. Their study, published in Nature magazine, also found that many of the genetic ancestors of today's mammals existed at the time of the dinosaurs - much earlier than previously thought - but in very low numbers. Dr Kate Jones, of the Zoological Society of London, said: 'Vitally, scientists will be able to use the research to look into the future and identify species that will be at risk of extinction. 'The benefit to global conservation will be incalculable.'
[The Metro Apr13,2007]