Is there evidence for design in biology? Or for that matter, what would constitute evidence of fine-tuning in biology?

This is the next question arising as we continue on with Chapter 13 of Alister McGrath’s book A Fine-Tuned Universe: The Quest for God in Science and Theology:

If there is any question guaranteed to excite some controversy in the science/faith debate this is it. After all – fine-tuning leads to intelligent design and intelligent design to creationism. Well, in the minds of some the connections are obvious – both those who wish to discern empirical evidence for the hand of God in creation and for those who insist that science disproves the existence of God. 

On one level “fine-tuning” in biology is obvious, imperfect, and a result of evolutionary mechanisms themselves.  After all, the premise of evolution is that nature fine-tunes itself. This is the standard Darwinian answer to questions about functional precision and design.  According to McGrath At first sight, the neo-Darwinian model seems to undercut any possible appeal to the biological domain as evidence of design or fine-tuning.” Even if we move beyond the reductionist approach of the selfish gene to a systems based approach there is still no need to invoke other than natural mechanism to account for the appearance of design and fine-tuning. But perhaps it is still the possible to discern fine-tuning in biology. The question is where to look. 

The question – what constitutes evidence for design – is by far the hardest question. It is difficult to pose a suggestion that is not inherently an argument from ignorance, either ignorance of mechanism or ignorance of method. 

The correct question is not “Is our current understanding of neo-Darwinian evolution by random mutation and natural selection sufficient to explain this feature or phenomenon?” but “Is there a natural explanation for this feature or phenomenon?” If someone someday demonstrates that neo-Darwinian mechanism is insufficient to produce some phenomenon it neither disproves the general features of evolution nor demonstrates design.

The complex structures and functions we observe in biological systems are marvelous and intricate. But it seems unlikely that any biological feature at this level will provide robust evidence for fine-tuning or design beyond that capable of natural explanation. But this doesn’t preclude the presence of fine-tuning in biology.

McGrath suggests that evolvability itself may provide evidence of fine-tuning.

Is the capacity for Darwinian evolution, which many hold to ba essential to any definition of life, itself an anthropic phenomenon? Life is fundamentally a physicochemical phenomenon, and as such it depends upon the fundamental laws of physics and chemistry, as well as the availability of fundamental materials required to achieve certain biologically necessary outcomes. … Is the very phenomenon of evolvability itself dependent upon certain predetermined parameters which, if these were to have been significantly different, would have prevented or subverted this critical faculty?

This point is consistently overlooked in many accounts of evolution, which seem to treat physics and chemistry as essentially irrelevant background information to a discussion of evolution. Yet this biological process requires the availability of a stable planet, irradiated by an energy source capable of chemical conversion and storage, and the existence of a diverse array of core chemical elements, with certain fundamental properties, before life can begin, let alone evolve. … There is an implicit assumption that life would adapt to whatever hand of physical and chemical cards were dealt to it. Yet this is untested and intrinsically questionable.

… The capacity of evolution to fine-tune itself is thus ultimately dependent on fundamental chemical properties which in themselves can thus be argued to represent a case of robust and fruitful fine-tuning. (pp. 180-181)

What do you think of McGrath’s suggestion?

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