Lemurs reveal clues to ancient Asian roots. (Science News of the week).

Bug-eyed primate cousins of monkeys and apes, lemurs currently live in the wild only on the African island of Madagascar. About 30 million years ago, however, a diminutive lemur species inhabited what is now central Pakistan, a new fossil find suggests.

The handful of teeth unearthed in Pakistan's Bugti Hills represents the oldest known lemur, contends an international team led by paleontologist Laurent Marivaux of Universite Montpellier in France. This discovery raises the possibility that lemurs originated in southern Asia, not in Africa as many investigators have assumed.

Only further fossil finds on both continents will unravel the evolutionary roots of so-called strepsirrhine primates, which consist of lemurs and their close relatives the lorises, the scientists conclude in the Oct. 19 SCIENCE. "The time has come for the Asian scenario to receive more serious attention," Marivaux says.

In sediment previously dated at approximately 30 million years old, researchers found 18 teeth from the ancient lemur species, which they dubbed Bugtilemur mathesoni. They argue that the shape of these specimens indicates that Bugtilemur bore an evolutionary relationship to the modern dwarf lemur.

Crucial elements of the comblike set of teeth that juts from the lower jaw of living lemurs and lorises appear in Bugtilemur, the researchers hold. For instance, a thin, flattened fossil tooth with a scoop-shaped inner surface resembles the lower canine tooth of today's strepsirrhines, they say. Moreover, Bugtilemur's cheek teeth display unusual features, such as a triangular shape and midtooth indentations, which also are found in the modern dwarf lemur.

"This is pretty compelling evidence for the earliest strepsirrhine in the fossil record," remarks D. Tab Rasmussen of Washington University in St. Louis. "Overall, the teeth look like those of a primitive mouse lemur or dwarf lemur."

The discovery of teeth from this ancient primate intensifies the mystery over when and how lemurs reached Madagascar, Marivaux's team notes.

Geological studies indicate that around 88 million years ago, Madagascar broke off from the Asian mainland at what is now India. Yet several genetic analyses of living primates suggest that the first lemurs evolved about 62 million years ago, and direct ancestors of modern lemurs originated between 46 million and 38 million years ago.

If those estimates prove accurate then ancient lemurs had to cross a water barrier to reach Madagascar. Some researchers theorize that a few African lemurs floated to Madagascar on thick clumps of vegetation.

In contrast, a 1998 genetic analysis concluded that lemurs and lorises originated about 87 million years ago. If that estimate bears out, lemurs may have inhabited Madagascar before it separated from the mainland, Marivaux says.

The new find also plays into an ongoing debate over whether the earliest primate ancestors of monkeys, apes, and people evolved in Africa, as researchers have long thought, or in eastern Asia (SN: 11/11/95, p. 309).

Scientists who study ancient primates are intrigued by the new find but emphasize that it remains unclear how lemurs and lorises evolved.

The discovery of lemur teeth from so long ago in Pakistan doesn't establish that lemurs initially inhabited southern Asia and then moved on to Africa, Rasmussen says. Previous fossil evidence shows that, at the time Bugtilemur lived, the same species of tarsiers and other small mammals inhabited both Africa and Asia, he points out.

Gregg F. Gunnell of the University of Michigan in Ann Arbor cautions that even though Bugtilemur's teeth look like those of modern lemurs in some respects, in other respects they resemble those of a separate group of ancient primates called adapids.

Says Gunnell, "This is a very important find that raises new questions about the origin of strepsirrhines."