Thanks for the food for thought. The idea of raptors inflicting this damage themselves motivated me to ask a friend who's been a falconer for more than 40 years about this, and his response was this: "never have I seen a raptor groom off it's sheath, never mind damage the bone beneath." He's kept eagles, hawks, and falcons of all sizes and sorts. Until there's some experimental work done on this, we can't support or deny this, but his observations are worthwhile.To begin with, who said anything about 'grooming off its sheath?' Not I! And, let's face it, there's no evidence that these 'cut marks' occur where one would want to cut to remove the sheath. As I will demonstrate below, to do so would have required cutting distal to the point from the keratin sheath grows. The 'cut marks' are evidently proximal to the anatomical location of sheath growth.
To demonstrate, I've scooped up a replica of an osteological specimen that retains the talon sheath, to see where the sheath grows from. Although these are clearly different species, the embryological origin of the anatomical structures would be very similar, if not identical [even if I don't presently have the data to support the contention]. As you can see, the sheath on the Combe Grenal talon on the right would not have grown onto the process of bone within the black square that the authors have superimposed to indicate the portion of the specimen where the putative cut marks are located.
|From Morin et Laroulandie (2012)|
|Credit Skulls Unlimited|
Thus, the falconer and anonymous are introducing a red herring by suggesting that no bird ever groomed off its sheath. In the case of the Combe Grenal avian phalanx the presumed cut marks occur where there would have been skin, not sheath.
Unless our falconer was in the habit of defleshing his dead birds, I doubt whether he would have seen the microscopic marks that the authors have discovered on what would have been the skin-covered portion of the talon. And even if he had, I doubt that he could have seen such marks without a powerful hand lens or a stereo-microscope such as the one the authors used to examine this specimen.
So, our falconer has proven to be of no relevance in our search for a process to explain these cut marks. The authors can assert, all they want, that the marks they observe would have been inflicted in the course of some symbolically mediated activity. However, if the gifted Neanderthal had wanted to remove the sheath, it might have been a better aim--these scratches would have done nothing to impinge on the keratinous covering.
Now let's have a look at the cut marks themselves. Close inspection of the authors' main figure reveals that the inset closeup of the marks doesn't accord with the photo of the whole specimen. In the illustration below, notice the dark furrow indicated by the red arrows. Now look at the closeup, C. Where is the dark furrow? Clearly the talon sheath wouldn't have grown above the dark furrow. Since the dark furrow doesn't show up distal to the incisions in C, I'm calling this further evidence that the so-called cut marks are not in the proper place if the intention was to remove the sheath. Moreover, the marks are so vanishingly tiny and so clearly V-shaped that they could have been inflicted only by a very thin, very hard, sharp object, such as a steel knife, or the teeth of a struggling rodent, a rock outcrop [perhaps even a flint outcropping!], or similar. I'm unaware of any claims for iron metallurgy in the Middle Palaeolithic [although, god knows, they're probably out there!]. Nevertheless, I imagine that these great birds got around as much as they do in the present, and thus it's not out of the question that such damage could occur naturally, and perhaps frequently, without our or the falconer's knowing.
Please don't think I'm suggesting that someone embark on a set of actualistic studies of dead raptor talons in support of more robust inference making with regard to these scratches. I find the whole idea silly, just as I find the notion that such a behaviour, if it had occurred meant anything at all about the Neanderthal capacity for symbolic thought. I still don't see why PLoS ONE saw fit to publish this so-called research.
Thanks to Anonymous for prodding me to take an even closer look at this silly claim. Call me unkind for calling it silly. Call me vicious, if you want. But at least you can't call me stupid, naïve, or gullible.