Weighing no more than 30 grams and spanning no more than 7 cm in length, it may be hard to understand why the fossilized remains of Archicebus achilles have the scientific world so excited but, as this is the oldest primate fossil on record, it most definitely is big news.
Archicebus – which means “ancient monkey,” but is a mouthful so from here on we’ll go with New Scientist’s delightful nickname, Archie — was actually found about a decade ago as a wonderfully well preserved skeleton but, because of the rigor required in reconstructing and analyzing the find, details hadn’t been published until now.
The Archie fossil was discovered in a quarry in central China’s Hubei Province. While the region’s current climate would be labeled subtropical, in Archie’s time, 55 million years ago, the area would have been a tropical wilderness.
It’s perhaps not surprising then that Archie appears to have been a tree-dweller that would have used a leap-and-grasp motion as it traveled its lush habitat.
The fossil indicates Archie had pointed teeth and likely got by on a diet of insects. The fossil’s large eye sockets present us with a creature that most likely had good vision for hunting in the day.
The fossil, about the size of a mouse, is 55 million years old, which makes it the oldest primate fossil on record. This carries a few heady facts with it.
Chiefly, this makes Archie the ancestor of all modern tarsiers, monkeys, apes and, indeed, humans. To understand exactly Archie’s place in the evolutionary tree, scientists have, quite helpfully, come up with the following image:
Archie, and scientists know this by virtue of its physiology, is not the last common ancestor shared by the above species, however it offers us a tantalizing glimpse at the divergence of monkeys, apes and humans from tarsiers — a pivotal point in our own history.
For one thing, Archie’s size suggests that our ancestors were also also small and adapted for tropical canopies. This serves to add weight to the revision of previous thought that primates at this time were already relatively large.
It also adds to the growing body of evidence that suggests early and major steps in primate evolution took place in Asia, rather than Africa.
This means that, at some point, Archie’s descendants diverged, one branch going on to evolve into tarsiers and the other the anthropoids (which would in time include humans). Anthropoids then made the journey to Africa where, eventually, humans evolved.
Dr. Chris Beard from the Carnegie Museum of Natural History in Pittsburgh, U.S., tells the BBC tells another reason why Archie is so remarkable:
“The heel, and the foot in general, was one of the most shocking parts of the anatomy of this fossil when we first saw it; because, frankly, the foot of this fossil primate looks like a small monkey, specifically like a marmoset.
“What it means is that the common ancestor of tarsiers and anthropoids had some features that looked more like anthropoids than tarsiers. And I guess we shouldn’t be so surprised by this.”
This remarkable discovery, and its place in the rich and one would think undeniable tapestry of evidence for evolution, unfortunately will not serve to deter the ongoing creep of creationism or so-called Intelligent Design that is infecting many U.S. classrooms.
Most recently, an Ohio school district has advanced classes on what is essentially creationism under the “teach the controversy” falsehood, as though to give the wholly unproven imaginings of creationists equal weight to the falsifiable yet countless robust pieces of evidence underpinning evolutionary theory.
Louisiana’s state legislature also recently killed a repeal of the Louisiana Science Education Act. Good, you might say, except the Act allows for supplementary materials that offer so-called “critiques” of evolution to also be given to children. This conveys the false notion that there are any such reputable critiques.
To be clear, while Archie does not immediately unlock our evolutionary past in all its glory, this discovery does give humankind the profound gift of seeing — actually seeing — another piece of our own history, something that creationism can never really do.
Image credit: Artist impression of Archicebus achilles by Xijun Ni, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences. Illustration of an evolutionary tree by Mark A Klingler/Carnegie Museum