Scientists get dander up in missing-link debate

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Predictions of a rhetorical bloodbath turned out to be nothing more than derisive laughter. And a presentation that had promised to cause "fur to fly" ended with but polite applause.

No notable monkey business occurred on Sunday inside the David L. Lawrence Convention Center. But a controversial question about whether a monkey-like fossil nicknamed Ida represents a link to humans continues to generate serious debate.

Does the complete primate fossil Darwinius masillae represent a "missing link" of early primates leading to great apes and humans? Or is Ida nothing more than an ancient lemur whose line represents a fossil footnote?

Philip Gingerich, a University of Michigan paleontologist, represents the group that researched the intact 47 million-year-old fossil and concluded Ida is from a line of early primates that pulled away from lemurs and sent primates down a course leading to monkeys, orangutans, gorillas, chimpanzees and, eventually, humans.

Speaking before a filled auditorium at the 70th annual meeting of the Society of Vertebrate Paleontologists in the convention center, Dr. Gingerich noted that Ida had primitive characteristics similar to lemurs. But he also presented seven other characteristics of Ida he said indicated a line to humans.

One distinguishing feature is its lack of grooming claws, which are not present in primates in the human line. That claw had to disappear at some stage, and Ida could represent such a stage of evolution.

"Is this a grooming claw?" he asked the audience, while presenting slides. "I'm going to hedge. It sure doesn't look like one. But as I said, I'm hedging."

Such statements generated some laughter.

The Ida research received heavy publicity, including high-profile articles, a book, a website and a television documentary, which don't typically occur when such discoveries are made or explained. That publicity helped elevate the debate, which Dr. Gingerich said he expects to continue until counter evidence emerges or his opponents agree with his evaluation of Ida.

One chief opponent to the Ida theory, Christopher Beard, curator of vertebrate paleontology at the Carnegie Museum of Natural History, said a primate he discovered in 1994, Eosimias sinensis, more likely represents a link to humans. His argument, he said, has garnered popular support among paleontologists.

Dr. Beard argued that a majority of paleontologists consider Ida to be nothing grander than an ancient lemur. Dr. Gingerich's talk provided no new evidence.

Dr. Beard said Dr. Gingerich prevented any fur from flying by giving a speech that allowed no time for questions. Dr. Beard said he had been prepared to challenge Dr. Gingerich.

One question, he said, is how Ida could have a fused jawbone when later monkeys in the human chain did not yet have fused jawbones?

Other arguments against Ida include claims the fossil doesn't show transitional features that would suggest a link to the human line. Others insist that the rock layers in which the nearly intact Ida fossil was discovered are too young to be from the age when such a link would have lived.

For those reasons, among others, Dr. Beard said Dr. Gringerich "has a long mountain to climb" to convince the majority of paleontologists that he's correct.

Debate is destined to continue.

But after concluding his talk, Dr. Gingerich said he feels the tide's been turning in his group's favor and registered surprise at language Dr. Beard and others have used, including claims of "outrage." Disagreements in paleontology, he said, usually are more polite.

"Usually people are more levelheaded when they speak," he said. "I can only conclude that we have hit a nerve. But that is not my problem. Let's keep it in perspective. Humans came from apes, and apes came from monkeys and there was something that came before them."

But Dr. Beard said what came before monkeys was not Ida.

"I urge him to look in the mirror and be levelheaded," he said.


David Templeton: dtempleton@post-gazette.com or 412-263-1578.


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