Chicane Or Chicanery? A Breath of Fresh Air on the Hybridization Front.

Neanderthal (silver) and modern human DNA (gold).

This comment from Nature News is satisfyingly subversive, but troubling, nonetheless. In its infancy The Subversive Archaeologist opined here, here, and again here that the then-recent conclusions of population geneticist Svante Pääbo and his team–beginning with publication of these data–was a load of hogwash. Based on the newly sequenced Neanderthal genome, his [their] claim was that the presence of identical genes in the ‘nomes–of the archaic and the modern human–demonstrated that the modern genome must have been the result of the two interbreeding. Breathtaking. No? Well, actually, no.   

Svante Pääbo

Despite the fancy mathematics and the tone of finality in the numerous papers on the matter [including, somewhat later, the Denisovan cohort] there’s nothing to be taken from their primary observations other than that we and the Neanderthals share a common ancestor. Full stop. And who took any notice of the Subversive Archaeologist? I think you can guess. Only you, dear Reader, and your fellow visitors to this blog.
     And so, Ewen Callaway’s very sensible note in the August 13 Nature News comes as a complete, and refreshing, surprise. Apparently others have raised similar doubts and similar arguments in response to the genetic work, which has been trumpeted near and far by John Hawks and numberless media outlets. Callaway’s summary of the debate, and her advertisement of the literature critical of the interbreeding hypothesis, represents for me a vindication that is both too little and too late. 
     Still, I’m encouraged by the Callaway article. My mother didn’t raise me to be a mathematician–least of all a population geneticist–which is why I, like most of my colleagues in palaeoanthropology, are mostly at the mercy of the twists and turns of argument and data that the gene-totallers publish. [Hence this blurt’s title.] Whether the interbreeding claim is just another chicane in the collective climb toward a more reality-based story of the past, or the inadvertent [even, perhaps, self-deluding] chicanery of gene teams like the 1000 Genome Project’s, most of us are forced back on our fundamental understanding of allele-frequency change through the generations, and, as well, our instincts. Neither is a comprehensively critical approach to the genetics, but it’s really all I’ve got in my defensive arsenal. 
     As for my absence from the published debate, blame it on my mother!
     I must to work. Catch you later.

Post scriptum: I’m humbled by the skill sets that I, an applied scientist who does archaeology, lack. There’s really nothing more productive of dismay than impotence in the face of others who’re au fait in areas that one isn’t. As I’ve previously whinged, archaeologists, moreso palaeoanthropologists, are hamstrung by gaps in their knowledge of the total breadth of disciplines that can be used in making inferences about the human past. For this reason alone, it’s imperative that we all approach new knowledge claims with a thoroughly critical eye. And if, as in my case, one lacks the knowledge to be critical of one approach or another, there is always the possibility of employing simple, informal logic when assessing newly minted knowledge. Such was the case in my approach to the latter-day claims that Neanderthals and modern humans interbred–I side-stepped the math and population biology models simply applied the fundamental principle of homology in confronting the matters that are covered in the Nature News piece.


Let Me ‘splain Somethin’ to You ’bout John Hawks, Svante Pääbo, and You, Lucy

I suppose I should just come out and say it, since there’s no point in being coy. The now-irrefutable evidence that you and I share varying amounts of apomorphic genetic material with the Neanderthals does nothing to settle the question of whether or not the Neanderthals and we might have, could have, would have, or should have had offspring together. 
     No good. 
     And here’s why.
     For a moment, put aside whatever ‘feelings’ you may have about the Neanderthals’ cognitive abilities compared with those of you and me. 
     About 100,000 years ago, at Qafzeh Cave, there are skeletally modern humans. A geological minute later there are Neanderthals a few km down the road at Kebara Cave. These two morphotypes may never have set eyes on one another. But the overlap in their territories, whatever the reason, means that there’s at least a good chance they bumped into one another. Which means that if they recognized each other as potential mates the strong likelihood is that they did the wild thing and had families.
     You can slice it and dice it, split hairs, and argue ’til you’re blue in the face, but the archaeological traces associated with each of these two species leads to the  robust inference that they behaved in the same manner. They produced Mousterian assemblages at each site, with a Levallois facies. If we had never found the skeletal remains at Kebara or Qafzeh, we archaeologists would no doubt have reached the same consensus–that those traces were left by hominids that were, more or less, behaviorally and cognitively identical.
     As you’re no doubt painfully aware by now, I have strong reservations as to the abilities of the Neanderthals, based on my ‘reading’ of the archaeological record. And, those of you familiar with my three (Yep, 3) solo publications will know that, when I speak of the cognitive abilities of the Neanderthals I’m also speaking of morphologically modern, but archaeologically identical, penecontemporaneous hominids such as those at Qafzeh. What many of you don’t know is that, if asked, I would also include Homo sapiens idaltu, at 160,000 kya and any other shape of hominid that left a similar archaeological record, regardless of their epoch. 
     I’m an archaeologist with a deep knowledge of evolution, human and otherwise. I’m also equipped with a modicum of knowledge in comparative vertebrate paleontology, geomorphology, pedology, animal bone identification, interpreting animal bone from archaeological sites, vertebrate taphonomy, site formation processes, lithic analysis, and informal logic. But I’m still just an archaeologist when it comes to the Middle Palaeolithic. 
     And, until such time as it’s possible to say that Broca’s Area unequivocally demonstrates that the owner possesses the ability to read this blog, or that we’re able to say that the FOXP2 gene unequivocally demonstrates that its owner possesses a similar ability, all that remains for anyone to use in understanding the abilities of those ancient hominids is the archaeological record. 
     Archaeologists are uniquely placed to interpret ancient behaviours from archaeological traces. Anatomists cannot. Vertebrate palaeontologists cannot. Geomorphologists cannot. Sometimes I really wonder if lithic analysts can. I am profoundly aware that my expectations and presuppositions of Neanderthal behaviour can clutter and colour my perceptions. That’s why I concentrate so heavily on the physical evidence and its context, because that’s the only way to move past my expectations in understanding the cognitive abilities of Middle Palaeolithic hominids.
     Along the way, if I find knowledge claims that don’t stand up, or represent, merely, one alternative explanation for the archaeological traces under examination, I’m compelled to point that out. There are so many extraordinary claims in the literature of the Middle Palaeolithic that it would takes decades of work like mine to really put the feet to the fire of those who’ve come before. I simply can’t stand by while the real howlers are allowed to remain in the archaeological corpus. 
     And you’re here to observe me at it. 
     So, to get back to the genome data. I’m in awe of the biochemical wizardry that John Hawks, Svante Pääbo, and their extremely adept colleagues are demonstrating. Yet, their documentation of the degree of relatedness between modern humans and the Neanderthals, or the Denisovans, means only that we share a common ancestor with the ancestors of those groups
     I’m very proud to say that it’s still up to the archaeologists, and they alone, to decide which Middle to Late-Pleistocene hominid morphotype or population gave rise to people like us, and when that occurred. As it was before the 1000 genome data became available, when it comes to Middle Palaeolithic hominid behaviour we have a lot of work to do before we’ve investigated every alternative explanation for each and every extraordinary claim that’s made about that distant time.
     I’m gonna go back to that task now.