Ida’s place in the primate family tree Close up of skull indicating Ida’s youth (less than a year old). Her milk teeth are visible and she shows teeth visible in keeping with plant and fruit eaters (Image: Jens L. Franzen; Philip D. Gingerich; Jörg Habersetzer1; Jørn H. Hurum; Wighart von Koenigswald; B. Holly Smith) Close up showing the lack of grooming claw familiar with other lemur primates (Image: Jens L. Franzen; Philip D. Gingerich; Jörg Habersetzer1; Jørn H. Hurum; Wighart von Koenigswald; B. Holly Smith)

Unbridled hoopla attended the unveiling of a 47-million-year-old fossil primate skeleton at the American Museum of Natural History in New York on 19 May. Found by private collectors in 1983 in Messel, Germany, the press immediately hailed the specimen as a “missing link” and even the “eighth wonder of the world.”


Google’s homepage evolved, incorporating an image of the new fossil – nicknamed Ida – into the company’s logo. Now that the first description of the fossil has been published, the task of sifting through the massive public relations campaign to understand the true significance of the new fossil can begin.

Ida forms the basis for a new genus and species of adapiform primate, Darwinius massillae. The adapids are a branch of the primate tree that leads to modern lemurs (see figure).

Ida’s skeletal remains are remarkably complete, putting her in a small, elite group of well-documented fossil primates from the Eocene (55 to 34 million years ago) that also includes her North American cousin, Notharctus.

Uniquely for primate fossils this old, Ida’s stomach contents and a few aspects of her soft anatomy are preserved. Like all adapiforms, Ida lacked a “toothcomb” at the front of her lower jaw – a structure that living lemurs use for grooming fur. Ida also lacked a “grooming claw” on her second toe, another difference from living lemurs. Otherwise, Ida’s overall proportions and anatomy resemble that of a lemur, and the same is true for other adapiform primates.

What does Ida’s anatomy tell us about her place on the family tree of humans and other primates? The fact that she retains primitive features that commonly occurred among all early primates, such as simple incisors rather than a full-fledged toothcomb, indicates that Ida belongs somewhere closer to the base of the tree than living lemurs do.

But this does not necessarily make Ida a close relative of anthropoids – the group of primates that includes monkeys, apes – and humans. In order to establish that connection, Ida would have to have anthropoid-like features that evolved after anthropoids split away from lemurs and other early primates. Here, alas, Ida fails miserably.

So, Ida is not a “missing link” – at least not between anthropoids and more primitive primates. Further study may reveal her to be a missing link between other species of Eocene adapiforms, but this hardly solidifies her status as the “eighth wonder of the world”.

Instead, Ida is a remarkably complete specimen that promises to teach us a great deal about the biology of some of the earliest and least human-like of all known primates, the Eocene adapiforms. For this, we can all celebrate her discovery as a real advance for science.