Washington, August 22 : A new study has rejected an earlier theory which had suggested that the dinosaur Tyrannosaurus rex evolved into a chicken.
A claim by researchers to have extracted proteins from a Tyrannosaurus rex bone and matched these to proteins found in chickens has been attacked in the same journal that published the original research.
In a withering critique, computational biologist Pavel Pevzner and his colleagues at the University of California, San Diego, say that the protein claim cannot be supported by the analytical data released so far.
The original articles, published last year in Science, claimed that palaeontologist Mary Schweitzer of North Carolina State University in Raleigh and her colleagues had recovered fragments of collagen from inside a 68-million-year-old T. rex femur bone - making the protein 100 times older than the previous collagen record holder, from a mastodon (Mammut americanum) that died up to 600,000 years ago.
A linked article described the analyses of the T. rex protein samples performed by John Asara, who runs a mass spectrometry research lab at Beth Israel Deaconess Medical Center in Boston, Massachusetts, and his colleagues.
Asara was able to match sequences from all the collagen fragments to those of living species including chickens, better defining the evolutionary link between reptiles and birds.
But Pevzner has called the article "computationally illiterate".
He argued that the mass spectrometry data on the seven proteins recovered are not broad enough to prove a statistically significant match with chicken collagen.
According to Pevzner, because Asara's team has not revealed all the 48,000 mass spectra data generated, it is impossible to rule out the 'false positives' that are routinely generated by the technique, and so tell whether the protein match is a mere coincidence like "a monkey typing random keys on a typewriter" that by chance spells words.
Surprisingly, even the T. rex protein samples have been questioned.
On 30 July, Tom Kaye, a research associate at the Burke Museum of Natural History and Culture in Seattle, Washington, asserted that the collagen extracted from the ancient bone was in fact remnants of bacterial slime.