A missing link in human evolution may have been filled by a remarkable fossil that could be the common ancestor of all apes and monkeys, including our own species.

Darwinius masillae, a small lemur-like creature that lived 47 million years ago, illuminates a critical chapter in the human story when the primate family tree split into two branches, one of which led ultimately to us. The fossil could even mark the point at which the evolutionary lineage of humans, apes and monkeys diverged from that of more distant primate cousins such as lemurs, lorises and bushbabies. Its anatomical features suggest that it lies close to the origin of the human branch and that the creature, or something like it, could be an ancient ancestor of humans.

The almost complete skeleton, which is missing only a part of one leg, was unearthed in 1983, in the Messel Pit near Darmstadt, Germany. Its significance had not been noticed before because the fossil was split into two parts. The pieces have now been reunited by a team led by Jørn Hurum, of the University of Oslo Natural History Museum. The first analysis is published in the journal Public Library of Science One. As well as the bones, the fossil preserves soft features of the animal such as fur, and even its last meal: it was a herbivore that ate fruit, seeds and leaves.

“This fossil will probably be pictured in all the textbooks for the next 100 years,” Dr Hurum said. “This is the first link to all humans . . . truly a fossil that links world heritage. This fossil is so complete. Everything is there. It is unheard of in the primate record at all. You have to get to human burial to see something that’s this complete.”

The ancient remains are those of a young female and the presence of both adult and baby teeth suggest that she was about nine months old. She was about 53cm (21ins) long from head to tail, and about 60 per cent grown when she died.

She has been nicknamed Ida, after Dr Hurum’s six-year-old daughter, whose adult teeth were erupting while her father was studying the fossil.

The scientific name honours Charles Darwin, as both the bicentenary of his birth and the 150th anniversary of the publication of On the Origin of Species fall this year. The second part is taken from the Latin for the Messel Pit.

Ida’s importance stems from her anatomical characteristics, which appear to mark her out as a transi- tional form between two types of primate. Modern primates are divided into two suborders: the strepsirrhines, or “wet-nosed” primates, include lemurs, bushbabies and lorises; the haplorrhines or “dry-nosed” include monkeys, apes and humans.

While some of Ida’s features are similar to those of strepsirrhines, she lacks two key characteristics of modern lemurs: a grooming or “toilet claw” on the second digit of her foot, and a fused row of teeth on the lower jaw known as a toothcomb. The absence of these traits is typical of haplorrhines such as human beings.

Jerry Hooker, a mammalian palaeontologist at the Natural History Museum in London, said: “Importantly, this new fossil lacks a number of key characters of lemurs and lorises, but also has a number of key characters of all other primates. Given that D. masillae was at an early stage in haplorrhine evolution, with a mix of primitive and only a few advanced characters, in life it probably looked generally more like a lemur than a monkey, but with a shorter snout and shorter hind limbs.”

Velsharoon wrote:Its worth noting that there is actually no proof, they just think it might be

True, but the implications are staggering and it certainly adds a new angle to evolutionary theory.

More on Ida: overblown claims and a worrying precedent

Now that the scientific details of Darwinius masillae are available for scrutiny by those who weren't given privileged advance access, some doubts are emerging. Not about the significance of the fossil per se -- it is a magnificent specimen and important -- but about the interpretation placed on it by the analysis team, and the hype that has surrounded the announcement.

There is a feeling out there that publication has been rushed, and that the data don't fully support the sweeping claims that are being made. As Henry Gee (@cromercox), Nature's palaeontology editor, put it on Twitter:

When something has been dead for 47,000,000 years, you'd have thought that they'd have spent a little more time on it at this end.

The issue is explained well by the brilliant Laelaps: it is far from certain that the adapids, the group to which Ida belongs, are the ancestors of modern monkeys, apes and humans. The consensus view is that the adapids were an evolutionary dead end, and that anthropoids (monkeys etc) are the descendents of animals that looked more like modern tarsiers.

As outlined in the paper "Evolving Perspectives on Anthropoidea" (among others) included in the recent Anthropoid Origins volume, it presently appears that tarsiers and omomyids are the closest groups to anthropoids. This is based upon a combination of fossil, genetic, and morphological evidence. This makes the adapid primates, including Darwinius, a more distant side branch more closely related to living lemurs and lorises.

The team behind the Ida discovery are claiming that adapids like Darwinius are actually members of the haplorrhine group, which contains anthropoids like us and tarsiers. But as Laelaps says, their evidence for this is extremely limited:

By moving the adapids into the haplorrhine group they can then make the claim that anthropoids evolved from the adapid stem and not tarsiers or omomyids. The problem is that they are using just one genus, Darwinius, to change the placement of an entire group without using any cladistic analysis! This is not good science.

The bottom line is that the hypothesis that Darwinius is closer to anthropoids than tarsiers or omomyids does not have strong support. Even though the authors of the paper constructed a very simple cladogram they did not undertake a full, rigorous cladistic analysis to support their claims. I am baffled as to how they could stress the significance of this fossil without undertaking the requisite research to support their hypothesis.

In short, while Ida is an important fossil, she isn't all that. The authors haven't presented enough evidence to support their claims.

This would be an issue even if this discovery had been announced in the normal way. But it's especially serious given the publicity blitz behind Ida. As I blogged yesterday, a popular book, a documentary, a website and an exhibition have been launched on the back of this find, before it has received full scientific scrutiny. The interpretation of Jorn Hurum and his team may well be wrong. But their story is all that most people are going to hear.

You have to wonder, as did Karen James in a comment on my post yesterday, whether this research was deliberately rushed, and submitted to a journal (PLoS ONE) with a less rigorous pre-publication review system than Nature or Science, to fit with the media schedule. And why did the journal agree to go along with this?

I'm also concerned that a worrying precedent has been set here. PLoS ONE, like most journals, normally release their papers to journalists under embargo, to give them good time to prepare a story and consult independent experts. That didn't happen this time: I was shown a copy by the production company working with the scientists yesterday morning, but I wasn't allowed to take it away from their offices. Many other reporters didn't even have that luxury, seeing the paper only when it went live on the PLoS website at 3.30pm.

For media outlets that had bought the rights, such as the BBC, it was a different story -- full access, weeks or even months in advance. Is it really right that full embargoed access to important and controversial research findings should be restricted on the say-so of the authors, to media that best suit their publicity strategy? Especially when money has changed hands?

Frazzled: No its just the skeleton of the first government employee who worked for DSS.

Cheese Elemental: I still don't believe in evolution, sorry.

Cheese Elemental wrote:I still don't believe in evolution, sorry.

Clthomps wrote:macro evolutions still has a large amount of holes in it.

Cheese Elemental wrote:
I have reason to believe in Charles Darwin's work, because he was a *bishop*, and a devout Christian.

There are holes in the data that serve to support the theory, but that is a wholly separate matter which has little bearing on the integrity of the theory itself.