Theory says that "morphological evolution reflects the darwinian process of natural selection, with evidence coming from numerous studies of contemporary populations and from classic interpretations of the fossil record." Selection does operate as an empirical reality, but ecologists have not found it as influential as Darwinians would like. The fossil record is "the fly in this darwininan ointment".
"In particular, statistical analyses of fossil data generally fail to confirm that natural selection strongly influences morphological evolution. Partly for this reason, a cadre of scientists is convinced that natural selection is less prevalent and important than typically assumed."
It is worth pausing to reflect on the word "cadre". Some may think that it signifies a small number of people, which is a valid but inadequate meaning. Other relevant ingredients are 'committed' and 'a nucleus capable of expansion'. There is a recognition here that selectionists do not have the floor to themselves - something previously noted here and discussed by Jerry Fodor here. This is a big concession, because the stance most commonly taken by Darwinists is that evolutionary theory with natural selection playing only a minor role is unthinkable.
The fossil record is the fly in the "darwinian ointment" - but is the problem bigger than this?
The case study chosen by Andrew Hendry in his News & Views essay on this topic concerns the threespine stickleback. The spines have a defensive role against predatory fish. Some exhaustive research has taken place to document how the number of dorsal spines and other related morphological traits varied with time after the last glaciation. The sticklebacks appear to have colonised a lake with few predatory fishes. The hypothesis is that if there is a metabolic cost of maintaining the number and size of these defensive spines, then, in the absence of predation, natural selection will lead to a reduction in the number and size of the spines. The hypothesis needs testing, of course, and this is where the problems surfaced.
"Up to now, few studies have been able to reject randomness; and those that have point to stabilizing selection, rather than directional selection. Taken at face value, these results might suggest that organisms have evolved their distinctive phenotypes without much aid from directional selection. If so, darwinian mechanisms might not be particularly important in generating the diversity of life."
Past statistical analyses concluded that the stickleback spines' hypothesis was not confirmed. Darwininsts are not comfortable with the outcome because they routinely use case studies like this to extrapolate from ecological fine-tuning to "generating the diversity of life". (From an ID perspective, the hypothesis is not unreasonable, but let it be fairly tested. What ID advocates do not do is indulge in large-scale extrapolations like this).
So now we come to the point of Hendry's essay. What he wants to say is that the "evidence has been there all along: we just haven't been looking properly". He refers his readers to several papers by Hunt which have resulted in confirmation of directional selection.
"One of Hunt's refinements was to overturn the usual burden of proof, wherein randomness has been assumed by default and retained as the evolutionary inference unless overwhelmingly rejected in statistical tests. But there is no biological reason for this a priori ascendancy of randomness, and randomness is extremely difficult to reject with the existing methods. [. . .]
First, Hunt et al. start their analysis at exactly the point in time when each armour trait begins to decrease, which favours a model of initially strong directional selection. But this choice does not undermine their general conclusion, because the standard methods could not reject randomness even when started at these same times. Second, the analysis of the stickleback data formally examined only one model of selection - the hybrid directional-stabilizing model they expected beforehand. The authors are here again stacking the deck for success in confirming selection. But then this is the point. Their analysis is akin to a positive control in showing that a new statistical method can infer the correct evolutionary process when that process is almost certain to be acting."
In other words, the analysis is being changed to yield an outcome that reflects the "correct evolutionary process". There is an overt "stacking the deck for success" because the researchers are supremely confident of the outcome. This is a lesson for anyone puzzling over statistical analysis: by changing the starting points and the methodology, a set of figures can yield outcomes which others have not seen! Hendry thinks this is progress:
"This work will almost certainly generate additional support from fossil sequences for the action of natural selection. Perhaps more importantly, it will become easier for biologists to accept randomness when random models still receive the most support. This acceptance, however, needs to be tempered by the realization that selection can certainly generate patterns that look random."
Those of us who have no argument with natural selection as a mechanism operating in nature do not need to adopt Hunt's approach. We are concerned about the introduction of circularity. It is not a robust methodology to select analytical techniques that confirm the theoretical ideas of the researchers. Science needs to be much more objective than that.
But our greatest concern is with Hendry's closing comment: "Ultimately, we might hope for the emergence of general conclusions about the role of natural selection in generating the diversity of life." This is where the potential for circular arguments is high. Darwinism has led many seriously astray by confounding empirical observations of selection with a grand theory to explain the complexity and diversity of life. The numerous sub-hypotheses of Darwinism need to be subjected to critical scrutiny but this is rarely done because this is more than just an irritating fly in the ointment!
Darwin in the fossils
Andrew P. Hendry
Nature, 451, 779-780 (14 February 2008) | doi:10.1038/451779a
Abstract: Adaptation by natural selection is thought to drive evolution. Although it has been difficult to confirm this process in the fossil record, evidence has been there all along: we just haven't been looking properly.
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