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.