"Missing link" or major hype?

by Erin Wayman
Thursday, January 5, 2012

Jørn Hurum, one of the scientists that announced the fossil find on Tuesday. 2009 AETN.

A squirrel-sized primate that lived 47 million years ago in the rainforests of Europe may be the common ancestor of monkeys, apes and humans, according to scientists who announced the discovery of the “missing link” fossil yesterday at a press conference. The well-preserved fossil has been at the center of a whirlwind PR blitz, including a History Channel documentary airing next week and an upcoming book — yet some scientists say the bones don’t live up to the hype.

The fossil, named Darwinius masillae, was recovered from Germany’s Messel Pit, an ancient volcanic lake that is home to a treasure trove of perfectly preserved mammalian fossils. Jens Franzen of the Senckenberg Research Institute in Frankfurt, Germany, and colleagues determined the primate, which they named "Ida," was a young female, only about nine months old when she died and fell to the bottom of the lake. The fossilized bits of her stomach reveal her last meal consisted of a mix of fruits and leaves.

“This specimen is like finding the lost ark for archaeologists,” said team member Jørn Hurum of the University of Oslo Natural History Museum in Norway at the press event. “This fossil will probably be the one that will be pictured in all textbooks for the next 100 years.” That’s because the team believes Darwinius stands at the root of the evolution of anthropoids, the group of primates that includes monkeys, apes and humans. This is in contrast to some media reports claiming Darwinius is a missing link between humans and other apes. Darwinius is about 40 million years older than that period of primate evolution.

But the team’s announcement of its discovery yesterday isn’t completely in line with the science either, other scientists say. “There is a big discrepancy between what they say in the technical paper … and what they said to science journalists and the media,” says Chris Beard, curator of vertebrate paleontology for the Carnegie Museum of Natural History in Pittsburgh, Pa. “I find that troublesome.”

In contrast to the more sweeping press conference claims, the researchers suggested in a paper published yesterday in PLoS One only that the fossil is probably more closely related to one group of primates, called haplorhines, that includes both anthropoids and small nocturnal primates called tarsiers, instead of with another group of more “primitive” primates, called strepsirrhines (which includes lemurs, lorises and galagos).

But even that interpretation doesn’t sit well with some scientists. The problem is how Franzen and colleagues analyzed where Darwinius belongs in the primate family tree, says Dan Gebo, a biological anthropologist at Northern Illinois University in DeKalb. They place Darwinius with the haplorhines, in part, because the fossil lacks certain strepsirrhine features, such as a dental comb, a row of thin teeth that protrude from a strepsirrhine’s lower jaw. But a dental comb is a feature that only evolved recently in the strepsirrhine lineage and therefore the absence of that trait does not, by default, make Darwinius a haplorhine, Gebo says. And the traits Darwinius and haplorhines do share in common are very primitive traits, he says, traits that do not distinguish haplorhines from strepsirrhines.

Another problem is that the team did not compare Darwinius to any of the known early anthropoid fossils, Beard says. One of them is Eosimias, discovered in China. At 45 million years old, Eosimias lived at roughly the same time as Darwinius — and suggesting that an ancestor and its descendants lived at the same time doesn’t make a lot of sense, he says.

For now, some scientists seem more amazed by the amount of media attention the fossil is receiving than by the fossil itself. “I’m awestruck by the depth and breadth of the PR campaign this whole thing was wrapped up in,” Beard says. Gebo agrees: “I have never seen anything quite like this, especially given that the fossil interpretation is wrong.”

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