October 21, 2003

Dinosaurs got cancer

Bone scans reveal tumours only in duck-billed species.

by John Whitfield
Nature News

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Many dinosaurs had cancer, researchers have discovered.

Their tumours were like those of human patients, showing that cancer has been around, essentially unchanged, for a very long time. "Diseases look the same independent of what critter is affected," says radiologist Bruce Rothschild of the Northeastern Ohio Universities College of Medicine in Rootstown.

Rothschild's team travelled North America with a portable X-ray machine, scanning 10,000 dinosaur vertebrae from more than 700 museum specimens. They looked at such well-known dinosaurs as Stegosaurus, Triceratops and Tyrannosaurus.

Only one group - the hadrosaurs, or 'duck-billed dinosaurs' - suffered from cancer1. The team found 29 tumours in bones from 97 individuals of this herbivorous group from the Cretaceous period, about 70 million years ago.

Dinosaur tumours have been mooted before, but this is the first large-scale survey of them. The researchers found that some bones suggested to be cancerous were just poorly healed fractures.

It's not known for certain what made the hadrosaurs sick, although Rothschild points out that they ate conifers, which are high in carcinogenic chemicals. The structure of their bones also suggests they were warm-blooded, which might have increased their cancer risk.

"We know very little about dinosaur diseases," says palaeontologist David Norman of the University of Cambridge, UK. "Quite why hadrosaurs should be prone to lesions in their tails is a fascinating, if ultimately unanswerable, question." The animals might have been unusually long-lived, allowing more time for tumours to develop, he suggests.

The commonest growths were hemangiomas - benign tumours of the blood vessels that are present in about 10% of humans. "If I showed [the dinosaur bones] to a pathologist, he'd make the same diagnosis," says Rothschild.

The 3.5 metre species Edmontosaurus was most cancer-prone and was the only one with a malignant tumour. About 3% of its bones contained a lump of some sort.

Cancers have been found in everything from coral to budgerigars, but their frequency in most species is unknown.

Understanding what causes tumours in wild and extinct animals might help us to treat and prevent them in humans, says Rothschild. Studying museum specimens could shed light on how diseases have changed over time, he adds: "Routine X-rays would be very valuable in zoological and human collections."

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