Wednesday 4 January 2012

Wacky Wednesdays, Anyone? Craig et al. & Ancient Marine Lipid Residues in late Mesolithic Northern Europe

Every once in a while you come across an article that reinforces the notion of an ivory tower, where scholars and academics live and work in an environment sanitized against all connection with the real world, to say nothing of reality. Such an existence leads to lines of research and ultimately to conclusions that would encourage anti-intellectualism in even the staunchest defender of science.     
     A tip of the hat to Matt Bandy for pointing me to this paperBefore I uncap my pen on the research here discussed, let me say that I have no methodological, technical, practical or other disagreement with the authors' analytical results. My criticism arises not from the work itself, but from the way it's framed, and from the implicit beliefs about the past that are in evidence. This will require a little background. But first, the citation.
'Ancient lipids reveal continuity in culinary practices across the transition to agriculture in Northern Europe,' by Oliver E. Craig, Val J. Steele, Anders Fischer, Sönke Hartz, Søren H. Andersen, Paul Donohoe, Aikaterini Glykou, Hayley Saul, D. Martin Jones, Eva Koch, and Carl P. Heron. PNAS 108: 17910-17915.

Craig et al. pose their research against the
traditional view that new economic practices—based on the cultivation of cereals and the rearing of livestock—and cultural innovations—notably, pottery and new forms of stone tools—rapidly spread from centers of domestication as a “package,” completely transforming society in their wake; these elements are the major indices of the so-called “Neolithic revolution”... (p. 17910)
As evidence for their characterization of the conventional wisdom they cite V. G. Childe’s 1936 Man Makes Himself. As usual I must claim a good deal of ignorance where the literature on the Neolithic is concerned. However I wouldn't have thought the consensus was one that betrayed such a thorough misunderstanding of social processes. Nothing in life is that clear cut, much less in the change from one way of life to another. But, I stand to be corrected. It's possible that there is a vast literature created on the basis of this view of the Neolithic. Possible, yes. Likely, no.
     So, having hauled their straw man into a vertical position, Craig and Co. set their trap for Richards et al. To paraphrase the authors: if it's true that people everywhere, in lockstep, signed up to be Neolithics when they had the chance, forgoing everything they'd ever believed about the world and the way it works, then all it would take is one grain of evidence that Neolithic people continued to eat seafood to pull the intellectual rug out from under all the Neolithic archaeologists that ever held to that view. Hmmm.
     Granted, Craig et al. did have a real target in mind. Michael P. Richards, Rick J. Schulting, and Robert E. M. Hedges had earlier published 'Sharp shift in diet at onset of Neolithic' in Nature 425: 366, 2003, in which they claim to have evidence of a sudden and complete switch to agriculture in Britain between about 5200 and about 4500 BP. Indeed, their conclusion was that
...there was a sudden and marked dietary shift associated with the onset of the Neolithic period in Britain, arguing against a gradual uptake of domesticated plants and animals into Mesolithic society. Marine foods, for whatever reason, seem to have been comprehensively abandoned from the beginning of the Neolithic in Britain.
Richards et al.'s claim is made on the basis of carbon isotope studies of human bone across the Mesolithic to Neolithic boundary, approximately 5200 BP. 
     Had I been Craig et al. I probably wouldn't have bothered mounting evidence to counter their claim, since I think a good case could be made for questioning the evidence adduced in Richards et al.'s paper. See for yourself in their figure, shown below. 

From Michael P. Richards, Rick J. Schulting, and Robert E. M. Hedges ('Sharp shift in diet at onset of NeolithicNature 425: 366, 2003)

These results include a dearth of isotopic data for the Mesolithic as compared with that of the Neolithic--i.e. 8 individuals for the last 3000 years of the Mesolithic (or about 1 observation for every 375 years) as against 99 for the first 500-or-so years of the Neolithic (or about 1 observation for every 5 years). Note, also, that a mere 14 of the 107 individuals fall below the bone-collagen delta carbon 13 range represented in the Neolithic (in other words higher on the X axis). All 14 of them are from the Mesolithic, it's true. But their numbers are only suggestive of the differences pointed to in their text when compared with the bulk of the data. I'd be very surprised if a random sample of the British population alive during the 500-or-so years of this Neolithic window might not miss the rare marine-derived datum that could be expected based on extrapolations from the Mesolithic data spread over 4000-plus years. Statisticians: start your engines!
     Even if one were to disregard the questionable statistical value of a sample of 8 anythings, the disproportionate datasets should have set off alarms in the Nature referees, if not, surely, in the minds of the Scandinavian scholars who spent considerable time and effort to overturn the notion of a swift and utter change in diet at the Mesolithic--Neolithic boundary in Britain. 
     OK. So, let's look closer at the ancient lipids paper. Craig et al. examined the residues in 220 ceramic vessels from the late Mesolithic Ertebølle and Funnel Beaker 'cultures' in the western Baltic--100 pots with carbonized surface deposits and 133 with preserved absorbed lipids. 
From Craig et al. 2011. 
Results of the residue analyses confirm that a significant portion of the lipid molecules were marine in origin. Not all, as it turns out, were derived from domesticated plants or animals. So, Craig et al. consider the dragon slain and the case closed: people didn't adopt agriculture holus-bolus. Thus, their major finding is that
...the very success of farming as an economic practice and the rapid demographic expansion following its introduction may be attributable to the ability of incipient farmers to rapidly adapt to new ecological settings by combining food production with exploitation of local wild resources.
I suggest that the authors would have been well advised simply to point out the shortcomings of the bone isotope chemistry paper rather than trying to counter it with their own findings. And here is where I think the PNAS editor might have taken more care to examine the core arguments made in Craig et al., and not cared so much about the fancy 'science-y' bits.
     Fair enough. Craig et al. did demonstrate that marine resources were being exploited across the Mesolithic to Neolithic boundary in the western Baltic. And they're correct inasmuch as, logically, their research undermines what they say is the sweeping generalization masquerading as conventional wisdom that pottery in all places and at all times equals domesticated resources. So, battle won. War over. Not. Quite. It's really hard for me not to view their efforts as an attempt to unseat a straw man. 
     Even if Childe said it, and even if Richards et al. claim to have support for the idea in their weak data, it's still the case that none of the underlying motivation of Craig et al.'s paper makes anthropological sense. To think that the Neolithicization of Europe involved a complete abandonment of marine resources is just dumb [I said I wasn't gonna say that. I shouldn't have said that]. It's much more likely that the burgeoning populations of the late Mesolithic and early Neolithic over-exploited the near-shore resources in the blink of a geological eye following a relatively rapid conversion to a new way of life, thus making the dietary change appear instantaneous and absolute, and hence Richards et al.'s results. As I understand it, bone isotope chemistry bears evidence of the sum total of an organism's diet for a considerable period prior to its demise--it's a time-averaged effect that they're measuring. Not so the residue in a pot. All Craig and Co. can claim is that some pots from the period in question contain traces of marine exploitation in the residues left by the most recent foodstuffs stored or cooked in them. This paper is not a contribution worthy of PNAS

These papers remind me of what can happen when one bad inference leads to another, and another, and the lengths to which some will go to make their research appear 'relevant.' 

The avuncular Ofer Bar-Yosef once cheerfully informed me that Current Anthropology would publish 'almost anything,' which I took to mean that I shouldn't have been too proud when CA published, without revisions, my BA Honors essay as 'Grave Shortcomings: The Evidence for Neandertal Burial.' Roger Lewin said much the same about the calibre of research between the covers of CA when he paid me a visit to discuss my research while I was a Ph.D. student at Berkeley in the early '90s. So much for collegiality and objectivity!
The perspicacious among you will already have noted that it was O. Bar-Yosef, himself, who acted as the 'editor' for Craig et al.'s PNAS paper. Ofer is a Foreign Associate of the Academy, which is a well-deserved honour. And if his support of the work in any way greased the skids in the publication process, it's to his credit. But I have to ask: 'Anything,' Ofer? 
 * The term Ivory Tower originates in the Biblical Song of Solomon, and was later used as an epithet for Mary. From the 19th century it has been used to designate a world or atmosphere where intellectuals engage in pursuits that are disconnected from the practical concerns of everyday life. As such, it usually carries pejorative connotations of a wilful disconnect from the everyday world; esoteric, over-specialized, or even useless research; and academic elitism, if not outright condescension. In American English usage it is a shorthand for academia or the university, particularly departments of the humanities (Wikipedia).

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