Thursday, October 22, 2009

Ida, the fossil hailed as ancestor of man, 'wasn't even a close relative'

IT WAS billed as one of the most important fossil finds in history, a "missing link" that would challenge everything we knew about human evolution.

Darwinius masillae, the primitive primate that was unveiled to the world with huge fanfare and a Sir David Attenborough documentary in May, seems now to have been less of a missing link than an evolutionary dead end. Far from being an ancestor to humans, the lemur-like creature from 47 million years ago belongs to an entirely different branch of the primate family tree that has left no known descendants, research has indicated.

When Jorn Hurum, of the University of Oslo Natural History Museum, announced the discovery of the astonishingly well-preserved fossil, he described it as "the first link to all humans". He nicknamed the animal "Ida" after his daughter, and a promotional website, a film and a book claimed that she could have been the common ancestor of all modern monkeys and apes, a relic of a critical branching moment in human evolution. Sir David, who narrated the documentary, said: "This little creature is going to show us our connection with the rest of all mammals. The link they would have said until now is missing, is no longer missing."

The discovery of fossils of another similar animal from 37 million years ago has now cast grave doubt on that idea. Both Darwinius masillae and the new primate, Afradapis longicristatus, appear to belong to a different lineage, closer to lemurs than monkeys and apes, that died out without modern descendants.

A major analysis of 117 living and extinct primates found that neither new fossil belongs on the evolutionary path that led to the anthropoids - higher primates such as monkeys, apes and humans.

Erik Seiffert, of Stony Brook University in New York state, who led the study, said: "Our analysis provides no support for the claim that Darwinius is a link in the origin of higher primates, and instead indicates that, if anything, Darwinius is more relevant for our understanding of the origin of lemurs and lorises - which are our most distant primate relatives."

The findings, published in the journal Nature, will reignite controversy over the Darwinius fossil. While it sheds important light on primate evolution, the bold claims about its position as an ancestor to humans surprised many palaeontologists, who felt that the PR hype was not justified by the evidence. Critics said that Darwinius appeared to be an adapid - an extinct group more closely related to modern lemurs than to anthropoids.

There was also widespread dismay at Dr Hurum's decision to sell film and book rights to the discovery before it had been published in a peer-reviewed journal. That meant that his controversial interpretation was presented to the public before it had been tested by the scientific community.

The new fossils, the first of which were found by Dr Seiffert's team in Egypt in 2001, indicate strongly that this interpretation was indeed wrong. While Afradapis longicristatus and Darwinius have some anatomical features similar to anthropoids, Dr Seiffert's research shows that these must have evolved independently.

"We compiled a large dataset of anatomical observations, made across 117 living and extinct primates, including all of the fossil primates that have been proposed as possible early members of the anthropoid group," Dr Seiffert said.

"We used a computer program to find the primate family tree that provides the simplest explanation for the distribution of these traits. In that tree, adapiform primates like Darwinius and Afradapis are not placed close to higher primates, but rather are situated as closer relatives of the living lemurs and lorises."

Dr Seiffert said: "The PR hype surrounding the Darwinius description was very confusing. The uninformed observer watching the associated documentary certainly must have come away with a very different view - specifically that Darwinius truly was a critically important link in the origin of higher primates, if not the origin of apes or even humans.

"Documentaries are extremely important for public understanding of science, so scientists and the media need to work together to make sure that they have their facts straight, and that they are portraying a balanced view of the evidence. I think that the most responsible approach would be to create documentaries well after publication of scientific results.",25197,26244567-2703,00.html

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