Is Evolution Scientific (Part Three)

Ray devotes three full chapters of How to Know God Exists to biological evolution, so the chapter actually titled "is evolution scientific" doesn't have much to say about evolution in the strict sense.  As for whether evolution is scientific, Ray's answer would seem to be that evolution can be tested, but that those tests cannot possibly show that it is true, or probably true, although they can  show (his case for the existence of God depends heavily on the nonexistence of common descent with modification) that it is false.

Ray segues from his discussion of abiogenesis to his discussion of "macroevolution" with a discourse on DNA and the insistence that it is like a written text, except vastly more complicated.  This section is enhanced with a couple of quote mines, one  from the former atheist philosopher Antony Flew (not, prior to his conversion to deism, noted as an expert in biochemistry, genetics, or abiogenesis research), and one from Francis Collins, who, of course, believes in God, thinks that science can inform faith, and -- perhaps most to the point here -- has no problem at all with common descent and does not seem to have one with naturalistic abiogenesis (after all, an omnipotent God could presumably create laws of nature that enable life to arise spontaneously from nonliving matter through natural causes).

There's a philosophically interesting side point here: William Paley, the classic 19th century ID theorist, noted that "contrivance" (specified complexity) is something human designers resort to because of their limitations: they cannot achieve the results they want through any simpler means.  An omnipotent Creator should not have to resort to immensely complex mechanisms to achieve His ends.  Paley argued that God did so anyway in order to impress us with His greatness, but then, an omnipotent Being shouldn't have to resort to vast complexity even to impress us.  The complexity of DNA (including such features as disabled genes, fragments of endogenous retroviruses, and large swaths of DNA that can be excised with no discernible effect on the developing embryo), argue for a naturalistic origin of genes and the genetic code, not a supernatural, unconstrained one.

Anyway, Ray deals directly with evolution only by dealing with DNA comparisons between humans and other primates, and dismisses them by noting that we should expect similar structures and functions to employ similar blueprints.  Now, this argument has some impressive adherents: Jerry Coyne, in Why Evolution is True, argues on the same grounds that aside from "junk" DNA, comparative genomics offers only the exact same support for common descent that comparative anatomy does.  But there are many proteins, and functional genes coding for those proteins, that perform the same function in different species despite differences in sequence.  Thus, e.g. cytochrome-c seems to do the exact same job in E. coli, elk, and elm trees, yet it is not identical in all these species, nor are the differences random, nor do they seem correlated to differences in habitat.  Humans and pigs, as Ray notes, have numerous similarities, especially in our omnivorous diets, yet our cytochrome-c is identical to that of chimps and not identical to that of pigs.

The important thing in these comparisons is not merely "similarities."  It is, first, that the similarities (and differences) fall into a consistent nested hierarchy, a "family tree" pattern that is what we would expect from common ancestry but not at all what we would expect from common design and separate creation.  It is, second, that many of these similarities don't seem to have any functional importance at all, from the numerous pseudogenes associated with smell that don't work in humans but are still homologous with working genes in other mammals, to endogenous retroviruses (viral DNA inserted into sperm or eggs and inherited by descendants) that we share with other primates (and more of them with chimps than with other apes, and more with other apes than with monkeys, etc.).   There are myriad similarities between humans and chimpanzees that aren't explicable in terms of common design and are explicable in terms of common ancestry.