Friday, November 15, 2019

Todd Wood's Take on Danuvius

Todd Wood is always interesting to read, even if I don't share his chronological leanings.  He has thoughts on the new Miocene ape from Bavaria, Danuvius:
Based on the fragmentary remains, we make some really interesting observations about the anatomy of Danuvius. These apes had strongly opposed big toes, which would allow them to effectively grip things with their feet. Their tibiae (shinbones) have the kinds of joints that would allow them to walk upright, and their femora (thighbones) support that conclusion. These apes might have been in some way bipedal. The arm bones they found have traits that are associated with suspensory locomotion, like hanging from tree branches. The body size was fairly small, about the mass of a bonobo.
As I mentioned in my post, I think the evidence for bipedalism is vastly over-stated and, even if it can be shown that this “Extended Limb Clambering” is shared by other fossil ape finds from the region, there is no particular reason to think that these critters were ancestral to later hominins. It is entirely likely that they exhibited a separate adaptation to this particular style of locomotion.  Todd raises some other questions, though, that are not answered in the paper:
So why not address similarities of Danuvius to later fossil hominins? The authors are trying to establish a new means of locomotion that they call Extended Limb Clambering (ELC). So they compare Danuvius to living primates (where the authors know how they get around), and they're interested in comparing it to contemporary Miocene apes of Europe. But they're not all that excited about other comparisons to later fossil forms like Ardipithecus, Australopithecus, or Orrorin. They also don't relate their findings to later fossil apes in Europe like Graecopithecus or the Trachilos tracks, both of which have been linked to hominins or bipedality. Perhaps they don't think those things are worth talking about (maybe because they're skeptical of Graecopithecus like I am), but I guess I just don't agree.
I think that part of the reason that these questions are not raised is because there is so much of a gap between these finds, chronologically and geographically. There is simply with which to relate them. As Todd points out, the hominin status of Graecopithecus is dubious, at best, and, even if the Trachilos tracks are hominin, they are still quite a distance from Bavaria and six million years later in time.

For now, this fossil ape stands on its own.  If we find other evidence of incipient bipedality in other forms in the area and can relate them to later forms, then the picture might change.  For now, though, Danuvius is a very interesting, odd Miocene ape. 

Thursday, November 14, 2019

Upright Ape?

Multiple outlets are reporting on the discovery of a fossil ape that appears to have at least a partially facultatively bipedal stance.  Here is the Fox News version of events:
The remains of an 11 million-year-old ape suggest that our ancestors started to stand upright millions of years earlier, according to scientists.

A team of researchers claims the fossilized partial skeleton of a male ape that lived in the humid forests of what is now southern Germany bears a striking resemblance to modern human bones. In a paper published on Wednesday by the journal Nature, they concluded that the new species — dubbed Danuvius guggenmosi — could walk on two legs but also climb like an ape.

The findings “raise fundamental questions about our previous understanding of the evolution of the great apes and humans,” Madelaine Boehme of the University of Tuebingen, Germany, who led the research, told The Associated Press.
Here is how the Nature paper actually reads:
Here we describe the fossil ape Danuvius guggenmosi (from the Allgäu region of Bavaria) for which complete limb bones are preserved, which provides evidence of a newly identified form of positional behaviour—extended limb clambering. The 11.62-millionyear-old Danuvius is a great ape that is dentally most similar to Dryopithecus and other European late Miocene apes. With a broad thorax, long lumbar spine and extended hips and knees, as in bipeds, and elongated and fully extended forelimbs, as in all apes (hominoids), Danuvius combines the adaptations of bipeds and suspensory apes, and provides a model for the common ancestor of great apes and humans.
First, this is way-the-heck back there, some five and a half million years before the first actual evidence of bipedalism (Orrorin). Second, there are no “hip” remains. The only post-cranial remains are long bones.  Much is inferred.  In hominins, the femoral neck and the connection to the femoral head provide much diagnostic locomotion information.  The fossil remains for this region are very scant, consisting only of a partial head.  Much of the argument for even some bipedality rests with the tibial angle, to wit:
The near perpendicular tibial angle is a shared character between hominins and Danuvius and supports the inference of a habitual valgus knee position and bipedalism for the new genus.
I think a new genus designation is certainly warranted. I have grave reservations about the “bipedalism” designation. We have possible evidence from Crete at 5.5 million years for bipedalism in the form of footprints. That is as far north as it gets.  All of the other evidence we have for the emergence of hominins and bipedalism comes from North Africa.  It is far more likely that this represents an independent adaptation/homoplasy for this hominoid.   If we had more evidence from later in the Miocene or, better yet, the Pliocene, then this might carry more weight.