One of the most controversial aspects of the whole Darwinius kerfuffle has been the primate’s proposed status as “the ancestor of us all.” The fossil, named “Ida”, has been popularly touted as the “missing link” connecting us to all other mammals, but how can we really know if Darwinius fits this role? The truth is that we can’t, and it is nearly impossible to parse direct ancestor-descendant relationships among fossil vertebrates, especially when we’re talking about a fossil that lived over 40 million years before the first hominins evolved.
Indeed, the frenzy over Ida has just been made all the more unfortunate by the announcement of a fossil primate in the journal PNAS that is much, much more closely related to us. Called Anoipithecus brevirostris, this short-faced ape was recently discovered in 11.9 million-year-old (Middle Miocene) strata in Spain. It doesn’t have a book, a flashy website, or a prime-time TV slot, but it could have some very interesting implications for the origins of our ape ancestors.
During the Miocene the earth was, to an extent, a “Planet of the Apes.” There was a greater diversity of apes occupying a much wider geographic range than living apes, so much so that paleoanthropologists have long been debating whether apes first evolved in Africa or in Eurasia (with some, including our ancestors, moving back into Africa before seven million years ago and others dispersing eastward towards the Pacific). According to the authors of the new PNAS paper, Anoiapithecus may shed some new light on this contested question.
If we could see a living Anoiapithecus today it would look quite a bit different from the other apes you might see at the zoo or on television. While it did have some classic ape traits like the heavy brow ridges, low forehead, and large canine teeth, what sets Anoiapithecus apart is an extraordinarily short face. Its jaws did stick out a bit in front, but much less so than is seen in living great apes like gorillas, chimpanzees, or orangutans. (See comparison below.) This contrast can also be seen when the face of Anoiapithecus is compared to another Middle Miocene fossil ape from Spain described by some of the same authors in Science in 2004, Pierolapithecus. Pierolapithecus has a face that is more similar in proportions to living great apes (and also, oddly enough, the controversial hominid Sahelanthropus), while Anoiapithecus was a flat-faced ape. (See comparison above.)
Indeed, the facial features of Anoiapithecus make it starkly different from almost every other fossil ape known, but what extinct apes was it most closely related to? Unfortunately comparisons among fossil apes are limited by the fossil material available (many Miocene apes are only known from teeth and a few fragments), so even if you have a relatively complete skull or even skeleton you still have to compare it to more scrappy species and genera. This is especially problematic since the face of Anoiapithecus is so unique, but aspects of its teeth appear to make it an early hominid close to kenyapithecine apes like Equatorius and Kenyapithecus. If this hypothesis is correct, then Anoiapithecus would be an early member of the evolutionary group that presently contains us and the other great apes, the hominids.
The hypothesis that Anoiapithecus and Pierolapithecus are part of an early hominid radiation in Europe has some interesting implications. Based upon the relationship of these two apes to earlier apes found in Europe and Africa, the authors suggest that some kenyapithecine apes left Africa, gave rise to a radiation of forms in Eurasia (like Anoiapithecus), and that some of these early hominids migrated back into Africa to give rise to the ancestors of modern African apes and humans. Anoiapithecus and Pierolapithecus would not be our direct ancestors, but rather representative of an evolutionary radiation of which our ape ancestors were a part. The picture is still a little fuzzy, but the authors feel that a few million years before the first members of our species came “Out of Africa” our more ancient ape ancestors spread back into Africa from a layover in Eurasia. (Again, it would be interesting of Sahelanthropus and Pierolapithecus had a close relationship, as this would support the dispersal of at least some apes back into Africa even if they were not the ones that gave rise to the earliest hominins).
As the authors of the study note more fossil discoveries will be essential to testing this hypothesis. While they focus on Eurasia, it would be wonderful if more complete remains of Middle Miocene apes from Africa were discovered for comparison. Nothing is written in stone yet, but if the authors of this new paper are correct, Anoiapithecus and its kin could provide important clues to the evolution of some of our ape ancestors outside Africa.
Moya-Sola, S., Alba, D., Almecija, S., Casanovas-Vilar, I., Kohler, M., De Esteban-Trivigno, S., Robles, J., Galindo, J., & Fortuny, J. (2009). A unique Middle Miocene European hominoid and the origins of the great ape and human clade Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0811730106