Ida

Unveiled on 19 May 2009 in a blaze of publicity by Mayor of New York Michael Bloomberg at the American Museum of Natural History, “Ida” is the 47 million year old fossil remains of an Eocene primate.

Named for the six-year-old daughter of Norwegian palaeontologist Jørn Hurum, “Ida” is being touted as “the eighth wonder of the world”, “the missing link in human evolution”, “the lost Ark of archaeology” and “the scientific equivalent Holy Grail”. It is claimed that “Ida” will “be in all textbooks for the next hundred years” and it will affect palaeontology “like an asteroid falling to earth” (ironic because there is already an asteroid named Ida).

Others have said that the find “confirms” Darwin’s theory of evolution. Technically this is correct, but no more so than my dropping an apple and seeing it hit the ground would “confirm” Newton’s theory of gravity. I’d also like to know how something that has been found can be described as a “missing link”.

Shunning more prestigious publications such as Nature, Hurum and his collaborators published on 19 May 2009 in PLoS ONE, the open access journal of the Public Library of Science. “Ida” received the systematic name of Darwinius massilae (Darwin's creature from the Messel pit), to celebrate the bicentenary of Charles Darwin’s birth. The paper was immediately available over the internet for download, and was accompanied by a TV documentary entitled Uncovering Our Earliest Ancestor: The Link.

So what exactly is “Ida”, why has she caused so much excitement and is it justified?

The fossil was recovered in 1983 by a private fossil hunter at the Messel Pit, a disused quarry 35 kilometres from Frankfurt-am-Main, Germany. The fossil was split into two parts, which were sold separately. One part was sold to Dr. Burghard Pohl of the Wyoming Dinosaur Center at Thermopolis, Wyoming; the other part to a private collector. In 2007 the latter became available for sale and was purchased for a substantial price by the Natural History Museum of the University of Oslo (Norway). The two pieces were subsequently re-assembled and are in an astonishingly good state of preservation, 95% complete and missing only the left rear leg. Such is the state of preservation that the outline of the soft body and the contents of the digestive system are clearly discernable.

“Ida” is a juvenile female, retaining some of her deciduous teeth. Her sex is implied from the lack of a baculum, or penis bone. It is believed that she was about 9-10 old at the time of her death. She had a healed fracture of the distal end of her right forearm. This would have hampered her movements and possibly contributed to her death. Her climbing abilities would have been impaired. Unable to drink from water trapped by tree leaves, she would have had to venture down to the lake to drink. This would have been her undoing – in the Eocene the region was tectonically active and large quantities of carbon dioxide were sporadically released. This would have immediately suffocated anything in and around the water. “Ida” would then have fallen into the water and been preserved in the sediment deep at the bottom.

Her unusual state of preservation does give us considerable insight into the anatomy of an Eocene primate, but Hurum and his collaborators are claiming that “the skeleton’s features clarify morphologies that have been given critical weight in primate phylogeny, and call into question accepted wisdom about the origin of higher primates.”

Although genetic and other evidence now suggests that primates first evolved as long ago as 85 million years, primates of the modern aspect (i.e. possessing all the features of modern primates such as nails rather than claws) are more recent and first appeared around 55 million years ago. Traditionally the primates are divided into two groups, the prosimians (lemurs, lorises, bush-babies, aye-ayes and tarsiers) and simians or anthropoids (monkeys, apes and humans). However it is now believed that tarsiers are more closely related to the anthropoids than they are to the other prosimians. Accordingly most authorities now divide the primates into two suborders, the Strepsirrhini (“wet nosed”) and Haplorrhini (“dry nosed”) based on the defining feature of a rhinarium, the wet, naked surface around the nostrils of most mammals (e.g. cats and dogs). The Strepsirrhini possess this feature, but it is absent in the Haplorrhini. Among the living primates, the Strepsirrhini comprise the prosimians minus the tarsiers; the Haplorrhini comprise the tarsiers, monkeys, apes and humans.

In addition, fossil primates of the modern aspect are all believed to belong to one group or the other. 47 million years ago, there were two main primate groups in existence – the tarsier-like omomyoids and the larger lemur-like adapoids. The former are often claimed to be ancestral to the haplorrhines and the latter to the strepsirrhines. However it should be noted that these relationships are not universally accepted and attempts to resolve the issue have been stymied by the lack of conclusive fossil evidence.

Hurum and his collaborators are claiming that conclusive evidence now exists, and that it overturns the orthodox position. Darwinius massilae is claimed to be an adapoid, but it is also linked to the haplorrhines – and by implication, to humans – on the basis that it lacks a “grooming claw” and a “tooth comb” of lower incisors and canines, two features that are characteristic of strepsirrhines. By implication, the adapoids are haplorrhines, not strepsirrhines; and thus they rather than the omamyoids could be ancestral to the later anthropoids, including humans.

My view is that this is certainly interesting, but it is hardly earth-shattering to the man in the street. Furthermore the evidence is hardly conclusive – the fact that Darwinius massilae lacks two features characteristic of strepsirrhines doesn’t automatically make it a haplorrhine.

In short, “Ida” is a spectacular fossil of considerable interest to palaeontology, but she has been massively oversold. She is not another Lucy, Homo floresiensis, Taung Child or Turkana boy. This kind of hype is just “bad science” – once the hoo-hah has died down, people will say “what was all that about”, with the worry that discoveries of considerably greater significance could be ignored by the general public in the future. This has happened in the past. In 1973, the long-period comet Kohoutek was hyped as “the comet of the century”. Comets are notoriously unpredictable and in the event, Kohoutek failed to live up to public expectation, though it was observed from the Skylab space station – the first comet ever to be observed from space. Less than three years later though, a genuinely great comet did appear, Comet West. But the media, having got its fingers burned once, ignored it and as a result, very few people saw it.

Reference:

Jens L. Franzen, Philip D. Gingerich, Jorg Habersetzer, Jørn H. Hurum, Wighart von Koenigswald, B. Holly Smith (2009): Complete Primate Skeleton from the Middle Eocene of Messel in Germany: Morphology and Paleobiology, PLoS One.

© Christopher Seddon 2009