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According to Conway Morris, biological convergence provides clear and decisive evidence that evolution is limited in its possible trajectories and is therefore not haphazard. Here Conway Morris has the better argument than Gould. Nevertheless, Conway Morris is not content to stop there. He wants to use biological convergence also to argue that evolution follows "inevitable and preordained trajectories." This is a much stronger claim, and it brings him into conflict with the adaptationists, such as Richard Dawkins.
Adaptationists—who, unlike Gould, give pride of place to natural selection—have no difficulty accepting that evolution exhibits the very trends that Conway Morris argues for on the basis of biological convergence. Where Conway Morris and the adaptationists diverge is over the claim that these trends are value-laden and goal-directed. Adaptationists are perfectly content to say that evolution reinvents certain structures because those happened to be the structures with the best selective advantage.
What is Conway Morris' response? Not to offer a scientific argument, but to denounce ultra-Darwinists like Dawkins for suggesting that evolution is incompatible with religious faith. Indeed, Conway Morris turns the tables, charging that Dawkins' brand of Darwinism has itself become a religious faith:
The pronouncements of the ultra-Darwinists can shake with a religious fervour. Richard Dawkins is arguably England's most pious atheist. Their texts ring with high-minded rhetoric and dire warnings—not least of the unmitigated evils of religion—all to reveal the path of simplicity and straight thinking. More than one commentator has noted that ultra-Darwinism has pretensions to a secular religion.
Such prose is likely to score points with traditional religious believers, whom Dawkins has gone out of his way to antagonize over the years. Nevertheless, it does nothing to address the point at issue, which is whether evolution is indeed goal-directed or follows certain trends merely because it is constrained by natural selection. Here Conway Morris offers not an argument but an existential choice:
The complexity and beauty of 'Life's Solution' can never cease to astound. None of it presupposes, let along proves, the existence of God, but all is congruent. For some it will remain as the pointless activity of the Blind Watchmaker, but others may prefer to remove their dark glasses. The choice, of course, is yours.
Leaving aside whether the choice actually is ours (surely God's grace has something to do with it), this appeal to "congruence" is inherently unsatisfying. As Conway Morris leaves it, evolution is as congruent with his own religious faith as with Richard Dawkins's Blind Watchmaker. Indeed, despite having some traction against Gould's extreme contingency view, Conway Morris' argument from biological convergence has no traction whatsoever against Dawkins.
The reason is that Conway Morris' argument from biological convergence is inherently metaphysical rather than scientific. Indeed, it constitutes a marriage of teleology and Darwinism, and an uneasy marriage at that. Conway Morris' picture of evolution is this: evolution is a process (created by God) to achieve certain goals, not least the formation of humanity. To achieve those goals, evolution is limited to a fixed set of paths. Moreover, the mechanism for driving evolution along those paths is natural selection. (Note that in this picture, natural selection is not a creative agent but rather an engine that powers the evolutionary process.)
According to Conway Morris, biological convergence suggests that evolution is a goal-directed process limited to fixed paths. But this suggestion is not a scientific proposal. Biological convergence, as Conway Morris employs it, merely points to a metaphysical possibility, to wit, the possibility that evolution is teleological. The actual scientific evidence that he employs from biological convergence, however, at best shows that evolution is limited to fixed paths, not that it has goals.
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