But other anthropologists were immediately skeptical of the conclusions and began writing the responses that are being published this month.
"Just because it's a complete and well-preserved fossil doesn't mean it's going to overthrow all our ideas," says Williams, the lead author. "There's this enormous body of literature that has built up over the years. The Darwinius research completely ignored that body of literature."
That literature centers on the evolution of primates, which include haplorhines (apes, monkeys, humans, tarsiers) and strepsirrhines (lemurs, lorises). The two groups split from each other nearly 70 million years ago.
The fossil group to which Darwinius belongs the adapiforms have been known since the early 1800s and includes dozens of primate species represented by thousands of fossils recovered in North America, Europe, Asia and Africa. Some adapiforms, like North American Notharctus, are known from nearly complete skeletons like that of Darwinius. Most analyses of primate evolution over the past two decades have concluded that adapiforms are strepsirrhines, and not direct ancestors of modern humans.
The most recent such analysis, published last year in the journal Nature, concluded that Darwinius is an early strepsirrhine and a close relative of the 39-million-year- old primate Mahgarita stevensi from West Texas.
Nevertheless, the scientists who last year formally described Darwinius concluded that it was an early haplorhine, and even suggested that Darwinius and other adapiform fossils "could represent a stem group from which later anthropoid primates evolved."
For example, they note that Darwinius has a short snout and a deep jaw two features that are found in monkeys, apes, and humans.<
|Contact: Gary Susswein|
University of Texas at Austin