Human Descent from Lemurs? Could be, sortalike

Here’s one that’ll grab you. Via Discover’s 80beats science news blog:

A small, lemur-like creature may have been an early ancestor of monkeys, apes, and humans. A magnificently preserved fossil dating from 47 million years ago reveals an animal that had, among other things, opposable thumbs, similar to humans’, and unlike those found on other modern mammals. It has fingernails instead of claws. And scientists say they believe there is evidence it was able to walk on its hind legs [ABC News].

This from a study to be published in PLoS ONE tomorrow, and which will note that this fossil could be from a “stem group” from which higher primates evolved — though the researchers reportedly told the Times that “we are not advocating this.” There’s a great backstory:

The fossil was first discovered in 1983 in the Messel Shale Pit, an old quarry near Frankfurt, Germany that has long been a World Heritage Site because of its rich fossil beds. The specimen was excavated by private collectors but was then divided into two parts and sold; it was only two years ago that scientists reassembled the complete fossil and began studying it. Described by the Times as the “most complete fossil primate ever discovered,” the specimen is a juvenile female the size of a small monkey. Only the left lower limb is missing, and the preservation is so remarkable that impressions of fur and the soft body outline are still clear. The animal’s last meal, of fruit and leaves, remained in the stomach cavity. The fossil will be unveiled with much pomp and ceremony at the American Museum of Natural History tomorrow, and the History Channel will air a documentary about the find next week. The new research adds to an argument over which of two groups of ancient primates was the evolutionary jumping off point for apes and humans: Was it the tarsidae group, which gave rise to the big-eyed tarsiers found in southeast Asia, or the adapidae group, the precursors of the lemurs found in Madagascar? The latest discovery bolsters the less common position that our ancient ape-like ancestor was an adapid, the believed precursor of lemurs%u2026. %u201CThis discovery brings a forgotten group into focus as a possible ancestor of higher primates%u201D [The Wall Street Journal], says study coauthor Philip Gingerich.

I’ve been studying and pondering the human/ape split human split from other primates more and more lately — a subject that intrigues because it can suggest so much about why, for instance, we are such social beings, and whether we are more like, say, bonobos or chimps. Or now, lemurs. It’ll be interesting to see how this plays out. Update 3 hours later (May 18, 2009, 9:28pm EDT): It’s getting interesting more quickly than I thought. As Brian Switek at Laelaps notes in his post “A Discovery That Will Change Everything (!!!) … Or Not,” this discovery has been the subject of immense hype (which I somehow missed, perhaps because I’m not pegged as an anthro/evo blogger. I get brain hype instead.) Switek makes a good argument for skepticism:

“The most significant scientific discovery of recent times”, eh? What could it be? Life on Mars? Time-travel? Teleportation? The Higgs Boson? A diet cola that doesn’t taste absolutely awful? Well, no. It’s all about a little primate from Germany. … An exceptionally preserved fossil primate is pretty exciting, but that’s not why the publicist for tomorrow’s AMNH event wrote one of the most overblown press releases I have ever seen. … According to the authors of the paper Darwinius supports the hypothesis that anthropoid primates evolved from lemur-like animals. I have yet to see the paper, but I am skeptical of this conclusion. First, one of the main authors of the paper is Philip Gingerich, who has been maintaining the evolution of anthropoid primates from adapids for years despite evidence to the contrary. (See Chris Beard’s The Hunt for the Dawn Monkey for a good review.) This is directly related to the second problem, which is that adapids were strepsirrhine (popularly called “wet-nosed”) primates more closely related to modern-day lemurs, lorises, and bush babies. Instead anthropoids and the stock from which they arose are haplorrhines (“dry-nosed” primates), with tarsiers and an extinct group of tarsier-like primates called omomyids being much closer to them than the adapids. …. I have the feeling that this fossil, while spectacular, is being oversold. This raises an important question about the way scientific discoveries, particularly fossil finds, are being popularized. Darwinius is just the latest is a string of significant fossils to be hyped in the media before being scientifically described (or at least before that information is released to the public). Other recent examples include “Dakota” the Edmontosaurus, the pliosaur “Predator X“, and “Lyuba” the baby mammoth. I am glad that these finds are stirring excitement, but I am a bit put off by the way they are presented. Companies like National Geographic and the History Channel are taking a larger role in how these discoveries are being presented. Each of the fossils I mentioned above have had books, feature articles, documentaries, or some combination thereof produced about them before any scientific description of them has been published. These promotional materials make grand claims but are vague on details, which are reserved for later academic publications. This can potentially create problems for effective science communication.

Brian’s objections seem well-considered — and is quite rich with other links as well, and a good start on what sounds to be a lively discussion over the significance of both the discovery and its high-profile discussion.