Oct 22 2009

Ida Redux

Published by under Evolution
Comments: 3

Remember Ida? Back in May of this year, scientists unveiled a beautiful 95% complete skeleton of a 47 million year old extinct primate. This specimen, because of its age and quality, was sure to add a significant piece to the puzzle of primate evolution. And yet, it seems, the scientists got a little too over-excited and blew the popularizing of this find.

Ida was unveiled with much fanfare, complete with a dedicated website, a book, and a documentary. Some of the media soaked up the hype, while other outlets caught on to the fact that the scientific community was not getting being it, and in fact were trying to pull back on the reigns.

Well now a new paper in the journal Nature by an independent group of scientists makes skepticism of the original interpretation of Ida official.

The new paper, by Dr Erik Seiffert, describes a new find – a 37 million year old primate fossil from Egypt called Afradapis longicristatus. He compares this new find to Ida, which as I said is 47 million years old. The controversy is over where, exactly, to place Ida on the primate evolutionary tree. Early primate divided into two groups. The most primitive group are the adapiforms, which led to today’s lemurs and lorises. The other branch is the haplorhines, which led to monkeys, apes, and humans.

Dr Jorn Hurum and the other original authors of the Ida (the official species name is Darwinius masillae) paper argue that Ida is the oldest member of the haplorhines branch, essentially connecting them to the base of the primate phylogenetic branch. They hyped this conclusion by saying that Ida connects humans to the rest of the animal kingdom.

However, even at the time, other paleontologists criticized this conclusion as being flimsy and based on an incomplete analysis of the fossils and there relationship to other known extinct and extant species.

Summarizing his new research, Dr. Seiffert told the BBC:

“We have analysed a large data set based on observations we have made on almost 120 living and extinct primates and what we find… [is that] Darwinius and this new genus that we’ve described are not part of our ancestry.

“They are more closely related to lemurs and lorises than they are to tarsirs or monkeys, apes and humans. This study would effectively remove Ida from our ancestry.”

What this means, if correct, is that Ida and Afradapis both belong to a side branch that comes off of the branch of primates that led to lemurs, the adapiforms.

This is the kind of debate that usually follows the presentation of a new fossil to the scientific community. There will be dueling interpretations for a while, punctuated by reanalysis when yet new specimens are discovered.  The story will slowly unfold and solidify, but always subject to revision in light of new fossil discoveries.

In response Dr. Hurum is quoted as saying:

“It’s a very interesting paper, and – at last – this is the start of the scientific discussion around the specimen we described in May nicknamed Ida.”

Right – the start of scientific discussion. Then why the overdone media hype surrounding one interpretation of Ida – an interpretation that, it turns out, was not only maximally sensational but also a minority opinion among paleontologists. It would have been far better to present Ida as what it was and is – a beautifully preserved fossil. And then present the competing interpretations of the fossil as a genuine scientific controversy, and let the public gawk at the vigorous debate. Instead the public was fed a premature, and what might turn out to be dubious, interpretation as if it were solid.

Hurum continues to argue that Ida shares certain traits with haplorhines (the monkey/ape/human branch). Such shared traits may in fact indicate that Ida is a haplorhine. Meanwhile, Seiffert and others argue that these similarities are analogous, not homologous – traits that look similar because of similar adaptations, not shared ancestry. And that a more thorough analysis of other traits indicates that Ida is an adapiform.

I have no idea who is correct – this kind of detailed analysis is beyond my lay knowledge of primate paleontology. But I love watching working scientists work out these controversies – it’s a great way to learn science, to see it in action.

It’s just a shame that in this case the public was fed some predigested hype, making the actual process of science seem like a disappointment rather than the main attraction.

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