Dinosaur DNA claim may be a mistake

Jeff Poling

Scott R. Woodward of Brigham Young University in Provo, Utah, reported a year ago in 1995 that he had detected pieces of DNA from 80-million-year-old bones. He identified the fragments as part of the cytochrome b gene from dinosaur mitochondria.

Researchers from the State University of New York at Albany argued that Woodward almost certainly detected contaminating strands of human DNA. "Human DNA is probably the most common laboratory contaminant. It's exceedingly difficult to keep human tissue out of an experiment, because specks of dust have human skin and hair on them," says SUNY's Caro-Beth Stewart.

In the Nov. 30, 1995, Nature, Stewart and Randall V. Collura explain how human DNA could have contaminated Woodward's analysis. They discovered that several higher primates have multiple, imperfect copies of the cytochrome b gene, which jumped from the mitochondria into the nucleus as long as 30 million years ago. These nuclear inserts are nonfunctional.

When Woodward checked for human contamination, he compared the DNA strands against human mitochondrial genes, but the nuclear inserts had not yet been discovered.

Stewart and Collura's data confirm findings published in the May 26, 1996, Science. Hans Zischler of the University of Munich in Germany had identified pieces of the cytochrome b gene in the human nuclear genome and suggested that these nuclear inserts had contaminated Woodward's analyses of the dinosaur bone.

In the same issue, S. Blair Hedges of Pennsylvania State University in University Park identified the strands as human on the basis of a phylogenetic analysis. The bone DNA more closely resembles DNA from humans than DNA from reptiles or birds, the nearest living relatives of dinosaurs. "All of the evidence suggests that it is contamination," comments Hedges.

Woodward did not construct an evolutionary tree to check how closely the bone DNA segments resembled human DNA, because, he says, the strands are too short for meaningful phylogenetic tests. Despite the new findings, he discounts the contamination theory. "I still think what we have represents an ancient DNA segment from the bone."