Panda pedigree: giant and lesser.

Are they bears or raccoons or members of yet another family? The phylogeny of the giant panda and its smaller relative, the lesser or red panda, has puzzled biologists for a century. The giant panda looks like a bear with some unusual characteristics and behaviors. For example, it does not hibernate and, instead of roaring, it bleats. the giant and lesser pandas have been grouped together because they share characteristics of tooth structure, skull architecture, penis shape and fur color pattern. Now scientists at the National Zoological Park in Washington, D.C., and at the National Cancer Institute in Frederick, Md., have applied tools of molecular biology to the pandas. They have compared the chromosomes, the DNA sequences and two sets of protein characteristics, the size and charge and the antibody-binding properties. Stephen J. O'Brien and his colleagues have constructed "consensus phylogeny," indicating that the giant panda is a bear and the lesser panda is a raccoon.

Between 30 million and 50 million years ago, the progenitors of raccoons and bears split into two lineages, the scientists report.

Soon the raccoon line divided further into the Old World raccoons (ancestors of the lesser panda) and New World raccoons (ancestors of the raccoon, coati, olingo and kinkajou). Meanwhile, in the bear lineage, about 20 million years ago the giant panda ancestors split from the main line. O'Brien and his colleagues comment in the Sept. 12 NATURE, "The lesser panda and giant panda clearly do not share a common ancestor after the [bear-raccoon] split, emphasizing that the morphological similarities of the pandas are probably the result of parallel retention of ancestral characters that may have been lost (for example, in the bear) after their divergence from the main line."