47-Million-Year-Old Fossil May Be Key Link to Primates and Early Human Primates

May 31, 2009

"We realized, when I was offered this specimen that it was the most complete primate in the fossil record," said Dr. Jorn Hurum of the University of Oslo, who led the two-year effort to determine the fossil's importance.

The fossil was unveiled May 19 at a news conference at the American Museum of Natural History in New York City.

The young female fossil probably resembled a modern-day lemur. Its body is about the size of a raccoon, but it has characteristics found in later primates and humans.

Instead of claws, it has fingernails, and it has opposable thumbs similar to humans. Non-ape mammals do not have opposable thumbs. The scientists said that by examining the structure of its hind legs, one of which is partly missing, they could see evidence of evolutionary changes that would eventually lead to primates standing upright.

The unveiling of the fossil is being accompanied by a book and a History channel documentary The Link.

One of the scientists on the team examining the fossil, Jens Franzen of the Senckenberg Research Institute in Germany said, "I don't think so, that we are dealing with a direct ancestor. We are not dealing with our grand, grand grandmother, but perhaps with our grand, grand, grand aunt."

In response to a reporter's question, Hurum also agreed that the fossil named “Ida” was probably not a direct human ancestor, but said he was comfortable with the find’s publicity.

"That's part of getting science out to the public - to get attention," he said. "I don't think that's so wrong."

The fossil was discovered in 1983 by amateur fossil hunters in a mile-wide crater called the Messel Shale Pit near Frankfurt that is a source of many other fossils from the Eocene Period – about 50 million years ago. Scientists believe that the pit used to be a volcanic caldera that trapped animals and preserved their remains. The amateur fossil hunters did not recognize its potential importance.

Hurum was shown the fossil by collectors, and then he had colleagues from Oslo and from the Senckenberg Research Institute help authenticate it. In order to make sure it would not disappear into private ownership, they bought the fossil.

The team of scientists examined the fossil for two years. They were able to keep their find secret until it was unveiled in New York along with the History channel’s documentary campaign.

X-rays show the animal was only about nine months old when it died and had a broken wrist. It had baby teeth, and adult teeth forming beneath them. The teeth are different from teeth of later great apes and humans. Modern children lose baby teeth around six-years-old and do not develop molars until several years later, according to Holly Smith of University of Michigan who joined the fossil team to examine its teeth. In general, she said “Ida” seems to have matured faster than its later relatives.

The fossil is much older than any of the human ancestors other scientists have found in what is now eastern Africa. The most famous African fossil that is generally accepted as pre-human, “Lucy” is more than 3 million years old.

A plaster cast of the fossil will be displayed in the NY Museum of Natural History, and the actual fossil is returning to Oslo.

“Ida” was named after Hurum’s six-year-old daughter.