(Click to enlarge)
The above illustration was posted by Prof Larry Moran in a blog post where he makes special note of the Cambrian Conundrum. What is the Cambrian Conundrum? Let me explain:
The blue profile in the illustration plots the graph of the very sudden rise in the diversity of phyla at the start of the Cambrian era (Phylum: a category of organisms with the same basic body plan). This sudden diversification was also accompanied by a parallel prolific diversification of classes (a class is a subdivision within a phylum) as shown by the yellow profile.
Shown as an overlay on the two aforementioned graphs is the “tree of life” as deduced from genetic molecular sequence analysis together with an assumed rate of mutation. Larry points out that the molecular tree of life fits in very well with the tree of life as determined from morphological analysis. But there is one big and obvious problem here: The molecular tree of life appears to show no obvious relation to the phyla and class profiles, profiles that are determined by observation on the fossil record. Why doesn’t the fossil record concur with the tree of life as constructed from molecular sequence analysis? How is it that this tree of life extends for hundreds of millions of years before the Cambrian and yet there is little in the way of fossil evidence prior to the Cambrian?
As a diehard evolutionist Larry is a good sport in being candid about this problem as he well knows that anti-evolutionists are attracted to this sort of thing like flies to an open wound. A couple of his correspondents give a stab at trying to explain this apparent inconsistency in evolutionary theory: One (schenk) suggests that chemical conditions prior to the Cambrian didn’t favour preservation: The other (nwrickert) submits the very interesting idea that the gene pool had developed to a point where the potential for sequence crossovers constituted a kind of “recombinant DNA laboratory” paving the way for a combinatorial explosion that gave organisms the DNA language needed to match a rapidly changing environment. I must admit I find this latter idea very appealing; it’s a special case of the more general idea that some “non-linear” bio-tech threshold was crossed at the start of the Cambrian ushering in a tremendous potential for change and development – in fact we see something similar with human society; farming, writing, industry, microchips and other technological changes entailed the crossing of thresholds that opened up huge vistas of possibility once the initial invention had made an appearance; these vistas were then rapidly explored resulting in rapid change.
But be that as it may, the fact is that there is an important lesson here for evolutionary theory. Evolution is a theory of a very complex object – namely, the history life. As such it has many degrees of freedom and adjustable variables. This implicit flexibility helps “rescue” evolution in the face of the sort of conundrum we have just looked at by allowing an adjustment of its many degrees of freedom until a fit to the dots of observation is achieved. But evolution’s strength in theoretical flexibility is also its weakness: Like some sprawling battle front evolution is vulnerable to myriad different kinds of attack on its many varied claims. In fact evolution is interdisciplinary and high level enough an object to be tantamount to a world view perspective. With byzantine objects like evolution there exists a constant tension between their vulnerability to criticism and the measure of latitude that comes of realizing that their complex ontology is never going to return the standard of observational “verification” we might expect of simple objects like Hooke’s springs and Newton’s gravity. The balancing act needed here is not easy to keep in the polarized North American environment where anti-evilutionists and atheist zealots are clawing one another’s eyes out in order to win their noetic battles. If with an eye on fair play one endeavors to be generous to either side one is then in danger of having one’s eyes scratched out by the other side.
In this connection I was fascinated by this post on PZ Myers’ blog where he tells his readers about theologian Alister Mcgrath’s comparison between the sense making facility of the conjectured Higgs boson and the theist positing Deity as a world view level sense making object. PZ Myers agrees that the Higgs boson is a valid theoretical sense making construction, but he takes Mcgrath to task for not taking the next scientific step; namely, that of proposing a test for deity; after all, says PZ, a lot of money was spent in order to test for the existence of the Higgs Boson; shouldn’t theists do the same for God?
Well yes, I’ll concede the admirable sentiment behind PZ’s remark, but in doing so I make all due allowance for the ontology of the objects we are proposing to test; that ontology may make these objects less than voluntarily accessible and/or give them a complex of adjustable variables that compromises the value of any number of tests; this in turn will impact the epistemological standards we employ. You see, whilst we may accept that PZ Myers' demand for a test is fair enough, we nevertheless should acknowledge that voluntary high standard testing at will is not an option with many real objects of study; historical objects are a notorious case in point; in particular evolution.
After all, it is clear that an object like evolution cannot be tested at will; as we have seen the fossil data needed to test for the existence of the conjectured evolutionary cladogram beyond the Cambrian is not forthcoming; it might, of course, come to light at some future date but that is not something over which we have control. Moreover, the conjectured extended cladogram may in fact not exist at all, and its absence explained by adjusting the parameters of history’s many degrees of freedom. (As a couple of Larry’s correspondents do; feasibly and plausibly in my view). In doing so, however, we are not using evolutionary theory predictively but instead invoking its flexibility to make post facto sense of the observed situation. Provided this is carried out with all due caution and awareness this post hoc practice is in my view perfectly legitimate science in the face of an absence of other choices. (See here for more comment along these lines: http://quantumnonlinearity.blogspot.com/2011/11/science-and-imagination.html )
It would be nice, of course, if we could test at will, or be lucky enough to have the necessary test data involuntarily fall into our laps, but unfortunately life is not always like that, particularly when the objects we desire to test shade over into the high level objects that are the stuff of world views. On balance, then, I would say that Mcgrath’s treatment of theism as a post facto sense making construct is rational enough given the ontological nature of deity; although having said that many Christians would claim that the ultimate (anecdotal) test of theism is in the tasting (Ps 34:8).
World view construction is largely a post facto activity that sometimes boarders on myth construction not because this is a rational ideal, but simply because force of epistemic circumstances make it so. Toy town science practitioners might find difficulty in accepting this inconvenient fact and may even be inclined to scratch our eyes out for breaching their narrow jot and tittle view of rationality. But then the purveyors of toy scientism are not the only ones unprepared to give leeway in the face of epistemic challenges. The zealous anti-evolutionists are in no mood to give all due allowance to evolution’s measure of post-facto sense making science. This is particularly ironic given that many anti-evolutionists are theists and that theism itself is not exactly the epitome of readily testable science!
The Right kind of scatching: If you scratch my back I'll scratch yours.