Monday 5 March 2012

Absence of Evidence. Evidence of Absence?

At any point does absence of evidence stand as evidence of absence? This question has bothered me since the first time I heard it used in relation to the archaeology of former times. Well, the answer, realistically, is that there is a point. There is a point beyond which this aphorism no longer applies, in practical terms as much as in scientific terms! Furthermore, never accepting absence of evidence as evidence of absence, has, I believe, led many, many scholars to accept what amount to myths about past people and our hominid relatives and progenitors.
     First consider the Sasquatch. Ignoring the hoaxes and attempted hoaxes, most reasonable people consider the absence of evidence to be as good as evidence of absence. Likewise the Loch Ness monster. Likewise the allegedly dead Paul. Likewise Russell's teapot. The great 20th century philosopher Bertrand Russell once attempted to explain his atheism with a similar argument:
Many orthodox people speak as though it were the business of sceptics to disprove received dogmas rather than of dogmatists to prove them. This is, of course, a mistake. If I were to suggest that between the Earth and Mars there is a china teapot revolving about the sun in an elliptical orbit, nobody would be able to disprove my assertion provided I were careful to add that the teapot is too small to be revealed even by our most powerful telescopes. But if I were to go on to say that, since my assertion cannot be disproved, it is intolerable presumption on the part of human reason to doubt it, I should rightly be thought to be talking nonsense. 
Despite Russell's confidence, it's still the case that, with capable investigative techniques it may well be possible to confirm the absence of the teapot. So, I much prefer the following crystalization, because it not only illustrates my point, but also goes beyond the informal logic to the place we get to IF we persist in rejecting the absence of evidence as evidence of absence.
It's one of the reasons we can pretty much make the assertion, "There Is No Santa Claus" with quite a high degree of reliability, despite it being a negative. For it to be otherwise leads to a whole host of rather unlikely conclusions about the real world. --Wikipedia
And that's my point. When we believe, for example, that purposeful burial occurred in the Middle Palaeolithic, instead of treating it like the open empirical question is truly is, it almost always leads to 'a whole host' of ampliative inferences about the belief systems and cognitive abilities of the hominids that were putatively responsible. Belief in that activity among the Neanderthals almost certainly emboldened the excavators of the Sima de los Huesos to claim, blithely, that the deadfall trap in which they found Homo antecessor was a place of ritual disposal of that hominds' dead--hundreds of thousands of years before the emergence of H. neanderthalensis and the Mousterian archaeological record.     
     Sure, in purely objective terms, purely logical terms, it's impossible to say that absence of evidence will ALWAYS be evidence of absence. But in the real world, highly probable usually suits us as enough to conclude that something either exists or doesn't. For gawd's sake the sun just might not rise tomorrow! Who's to say? But, to all intents and purposes, it's a fairly safe bet. Why is it never the case in archaeology? When I ask, 'Where are the Middle Palaeolithic cave paintings? Where are the pre-Clovis sites?' I might as well be asking 'Where are the Leprechaun remains? Where the Fairy cities?' And yet, someone will always repeat the mantra: absence of evidence is not evidence of absence. 
     I hope I've managed to puncture, or at least to create a slow leak, in that argumentative balloon. Now you know that the absence of evidence is often taken as proof of absence. To persist in believing otherwise can easily lead to fanciful constructions of past reality, something I would hope we'd all prefer to avoid.


  1. Thank you for your skeptical blog! I also think absence of (good) evidence can be evidence of absence. A seminal moment for me was when my undergrad prof RG Matson (UBC) noted that a search for Pleistocene archaeological sites had begun in Australia and the New World about the same time. Within a decade, there were dozens of uncontroversial sites found in Australia; but none in the Americas. Not proof, but pretty damning! This is really still the case three decades after that lecture.

    Skepticism is eerily silent all too often in archaeological discourse, at least publicly. Of course, whistle blowers often end up being scapegoats as the mob doesn't appreciate hearing that it has been fooled, and you had better not be found living in a glass house! The media in general is all too eager to jump on almost any twaddle, so long as it sounds groundbreaking, unexpecteldy old, hi-tech, or potentially paranormal. So, apparently, are some of the large journals, that seem to have published stories (like the nanodiamonds at the beginning of the Younger Dryas)that didn't stand scrutiny for long; where were the peer reviewers, or at least prominent dissenters? I think the Manis mastodon splinter was another case of a major journal overlooking Occam's Razor in order to publish something newsworthy. Now we have another pre-Clovis site that has phoenix qualities. I got very muted support for my skepticism over the Manis bone 'point' expressed in the superlative, and alas now mostly quiet, 'Northwest Coast Archaeology' blog of Quentin Mackie.

    I just found your site, and applaud it's jaundice!

  2. @Morley,
    Thanks for your support. One of the reasons I've come to appreciate this perch of mine is precisely that they can't come after me with anything other than a reasonable counter-argument. There has been, notably, only one who reads and contradicts semi-regularly, and usually forces me to hone my argument a bit. But only one. Amazing, really. As I know I've said somewhere in the archives, for the authors to respond would be tantamount to taking me seriously. And you and I both know that's unlikely ever to happen. But we have ways of seeing where the visitor originate. Curiously, shortly after I've posted on recent howlers, the hits from the authors' countries of origin are significantly increased. Either way I win--either they take me seriously and are worried that I'm right, and are therefore staying away, or they prefer to look as if they're ignoring me, and stay away. It's like year-round open-season on sillyness, and with no license fee!

  3. Paisley Cave, OR, for one, is a pre-Clovis site, and one that is very well-dated. I'm sure there are more out there. One of the lessons from Paisley Cave is that there is no clear sense of what a diagnostic pre-Clovis (or contemporary non-Clovis) lithic industry looks like. The pre-Clovis and Clovis age materials there all look more or less like Western Stemmed tradition, which goes well into the Archaic in the Great Basin. So without something as diagnostic as fluting to help identify pre-Clovis assemblages there is an absence of evidence simply because what counts as evidence has been wrongly defined. There's still much work to do before saying there is no pre-Clovis.

    As for nano-diamonds in the YDB, rest assured that the reviewers have been all over that in the archaeological community. Meltzer and Holliday's piece in CA recently is ample evidence that peer-review process did what it does with extraordinary claims. In that case, the idea that if there was an impact, it's not an archaeological problem, it's a problem for geologists", is an astounding statement from those authors. But indeed, other disciplines are looking into the geological record, and the case is not closed there either.

  4. Wouldn't Stanford and Bradley say that pre=Clovis should look like the Gravettian? :-) Which raises an interesting question. What is the evidence for backed artefacts in the Americas?

  5. I remember finding a Noailles burin in NW Queensland. It made me realise that Noailles burins are probably an indication of raw material shortage in the Perigordian sites where they are found. A colleague thought it might indicate that there should be 26 thousand year old sites in that region of Australia. Equifinality is a powerful force.

  6. @Spawn. Dead on about the presumed pre-Clovis. Although I have to admit, if the oldest Clovis point is around 11,500 RCYBP and the Paisley Cave poop is around 12,300 RCYBP, it is, technically, pre-Clovis, by about 800 RCY. But that may only be because the 12,300 RCYBP Ur Clovis point hasn't been found yet. You see, it's like I always told ya, absence of evidence isn't evidence of absence! That darned 12,300 RCYBP Clovis point will turn up someday and we'll be back to square one!

  7. I have always been puzzled that there is such determination in north American archaeologists - not to find Pleistocene sites.

    In Australia this was true up until the late 1960's. I know of Edmund Gill who was told by his Museum Director not to claim the Aboriginal people were in Australia well before a few thousand years ago because such claims "would bring the Museum into disrepute". In Australia the real issue is 40k or 60k and how you prove it.

    I am not surprised that IainD found burin's because those describing Aboriginal stone tools simply applied the labels and descriptions from Europe to Australian stone tools. The reality as Brian Hayden discovered was far more casual and thus all the categorising may in fact mean nothing.

  8. Just to avoid any incorrect inferences implied by IainS's post. I only found one Noailles burin. I knew of such things from my knowledge of the French Palaeolithic, and I had the identification confirmed by a leading French archaeologist. But I was never likely to say that the Australian object was usefully described by the typological label used for the French Palaeolithic, rather that the discovery of such an object in Australia confirms my view that equifinality is a persistent feature of the archaeological record, and that the discovery of such an object in Australia makes it very unlikely that one should appeal to a cultural interpretation of such objects when found in France.

    I have much more to say about Brian Hayden's PhD, but it is nice to hear of someone else who understands that what he showed was how fundamentally flawed it was to expect that the assumptions of European archaeologists can be met by simplistic experiments such as his. We learned that European typologies do not apply very well, not only in Australia, but probably anywhere.

  9. Dare I say that the French typologies may not even en France, as they say? .....

    Wait for it.

  10. I do like Paisley Cave evidence so far, even without the coprolites that didn't look wholey convincing from the images I've seen, but then I am certainly no expert there! (though we did find dog coprolites in a housepit excavation once, full of salmon bone.....). And I'm still leary of DNA evidence, it is SO easy to get contamination....

    But Paisley Cave is exactly the right age to represent people coming in from the coast (I do believe there must be pre-Clovis, but not by millennia) and the work looks to be very carefully excavated and documented from what I've gleaned from their website.


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