Preserved DNA reveals lineage of moas.

Centuries have passed since the last species of moa died, yet scientists have only now begun to unravel the genetic code of these extinct birds. By comparing ancient DNA samples extracted from moa remains with DNA samples from modern birds, researchers can put the moa in its proper place on the evolutionary tree.

This genetic study "sheds new light on the origins and evolution of these birds," says Alan Feduccia, an expert on avian evolution at the University of North Carolina at Chapel Hill.

Traditionally, biologists have placed the flightless moa with the modern ratites, the taxonomic group that includes other flightless birds such as ostriches and kiwis. Researchers have continued to argue, however, about the

moa's exact connections to members of this group.

Debate has focused in particular on the evolutionary relationship between moas and kiwis; many researchers have proposed the moa as the kiwi's closest relative.

Like the modern kiwis, which resemble a large chicken in size, moas were restricted to New Zealand. However, moas ranged from the size of a large turkey to over 3 meters high. Isolated from mammalian predators by the waters surrounding their home, moas prospered for millions of years. With the arrival of the first aboriginal people, however, moas began to decline until they became extinct several hundred years ago.

Modern biologists have had to reconstruct moa taxonomy indirectly from preserved bones and rare tissue samples - until now.

An international team of scientists has extracted and sequenced DNA fragments from ancient moa remains. This allowed the researchers to compare the genetic structure of the moa directly with that of modern birds, revealing that the moas differ in their origins from the kiwis. Details of this study appear in the September PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES.

The researchers conclude that, while clearly members of the ratite group, moas diverged from other ratites early in their evolution. Kiwis, on the other hand, appear closely related to the modern ratites of Africa and Australia. These divergent origins of New Zealand's birds raise the possibility that flightlessness evolved several different times among the ratites, the scientists conclude.

The team compared DNA fragments extracted from the remains of four different species of moa with comparable DNA sequences from eight modern species of ratite birds.

While similar studies have examined isolated samples from ancient animal and human remains (SN: 4/27/85, p.262), this is the first to look at DNA from both bone and tissue samples preserved under similar conditions, says team member Svante Paabo, a molecular biologist at the University of Munich in Germany. The researchers found that DNA seems to survive longer in bone than in soft tissue, perhaps because the minerals in bones may bind to DNA molecules, Paabo says.

The oldest DNA obtained came from a moa specimen approximately 3,300 years old, which had been naturally mummified in a dry cave. Few ancient remains still yield identifiable DNA, because DNA eventually breaks apart in the presence of water and oxygen, explains Paabo. He predicts that similar studies may soon reveal the evolutionary history of sabertoothed tigers from the tar pits of Rancho La Brea in Los Angeles, Calif., as well as frozen mammoths from Siberia. Paabo plans next to conduct a taxonomic study using DNA from the remains of extinct cave bears in Europe.