03 March 2008

Talking trash about "junk DNA": lies about "function" (part II)

The creator goes off on one wild, specific tangent after another, or millions simultaneously, with an exuberance that would seem to be unwarranted, and with an abandoned energy sprung from an unfathomable font. What is going on here? The point of the dragonfly's terrible lip, the giant water bug, birdsong, or the beautiful dazzle and flash of sunlighted minnows, is not that it all fits together like clockwork – for it doesn't, particularly, not even inside the goldfish bowl – but that it all flows so freely wild, like the creek, that it surges in such a free, fringed tangle. Freedom is the world's water and weather, the world's nourishment freely given, its soil and sap: and the creator loves pizzazz.
– from Pilgrim at Tinker Creek by Annie Dillard. Harper & Row (1974), p. 137.
Questions about the designs of the panda's thumb, the human appendix and tailbone, and male nipples should caution scientists against jumping too quickly to an evolutionary conclusion whenever some aspect of anatomy seems superfluous. The RTB creation model anticipates that future research into the anatomy of complex animal structures will reveal increasing, rather than decreasing, evidence for exquisite design and functionality.
– from Creation as Science by Hugh Ross, NavPress (2006), p. 170.
Can you tell which of the authors quoted above won a Pulitzer? Heh.

Back to the big lie about "junk DNA" as told by anti-evolution propagandists. The first theme in this cesspool of creationist folk science, as I described in the first installment of this series on "junk DNA", is this: that "junk DNA" is functional and therefore that evolutionary claims regarding its origin are mistaken. Two previous posts have tackled the first half of that howler, describing how creationist portrayals of "functions" for "junk DNA" are scandalously inaccurate. (The most disturbing installment, in which Hugh Ross is shown to have fabricated a bogus history of the study of "junk DNA," with physicists hilariously portrayed as heroes, will be posted separately this week.)

Now to the second half of this folk science fable. These deliberately misleading accounts of "function" for "junk DNA" are used by creationists in two ways.
  1. After falsely claiming that "Darwinian" biologists left non-coding DNA unstudied for decades, they assert that scientists using design-based approaches would never have made this mistake. This claim is irrelevant, at least because the premise is untrue, if not because design proponents would have left the entire bloody genome unstudied while giving lectures and writing books on the impossibility of evolution.
  2. After falsely claiming that non-coding DNA is "functional" despite "Darwinist" claims to the contrary, they assert that this evident "functionality" is evidence against common descent. This is a pretty ludicrous line of reasoning, but let's be clear on why it's wrong, because it's central to the folk science of "junk DNA."
Here's Fuz Rana of Reasons To Believe, summarizing an entire section of his discussion of "junk DNA" in Who Was Adam?
Evolutionary biologists maintain that the pseudogenes, SINEs, LINEs, and endogenous retroviruses shared among humans and the great apes provide persuasive evidence that these primates arose from a common lineage. The crux of this argument rests on the supposition that these classes of noncoding DNA lack function and arose through random biochemical events.
– From Who Was Adam? by Fazale Rana with Hugh Ross, NavPress (2005), p. 235.
That paragraph is excerpted from chapter 14, which is called "What About "Junk DNA"?" And Rana's claim throughout that chapter, as well as on the RTB website, is that a "supposition" of non-function is central to the explanation of common descent with regard to non-coding DNA.

I'm at a loss as to how to characterize Rana's misconduct here. As before, when I've confronted folk science on this blog, I'm struggling to understand how a Christian with even mediocre integrity would consider writing something like that. It can't be that he's stupid or ignorant enough to actually believe it. This is folk science, and it's bad.

To be brief: biologists make neither of those suppositions when they use non-coding DNA elements to establish common ancestry and particular evolutionary relationships. Whether or not a certain DNA element is "functional" doesn't make it any less an indication of common descent, nor have biologists ever assumed universal non-function of non-coding DNA in the first place. (The details of the reasoning actually employed by real scientists in this area will be the topic of the next post in this series.) Rana's continuous assertion that non-function is the "crux" of the phylogenetic argument is subtly disingenuous. (I think the subtlety of the ploy will be clearer as I continue the series and discuss specific types of non-coding DNA and what is known about them.)

Pseudogenes and mobile elements constitute overwhelming evidence for common ancestry, not because of "presumptions" regarding their function, but because they exhibit patterns of inheritance and location (within the genome) that are best explained by common descent. Even if a particular mobile genetic element has been put to work by the genome in which it is embedded, its conserved location in particular lineages (and not in others) presents an observation that is readily explained by common ancestry. In other words, even when it's true that a particular piece of non-coding DNA has a biological function, it's not true that this falsifies the basic explanation of common descent.

The fact that many non-coding DNA elements are known to be non-functional only makes Rana's position more laughable. Consider, for example, the GULO gene, which is necessary for the synthesis of vitamin C. You may be surprised to learn that, among mammals, only humans and their primate cousins, plus guinea pigs, require vitamin C in their diets. All mammals have a gene called GULO in the same general location in their genomes. But in primates, that gene has been mutated in a specific way, rendering it unable to make a functional protein. And in guinea pigs, the gene has been mutated differently. I'll present more examples in the final post in this series, but here's the point of including one in this post: primate species with the same dietary oddity (need for vitamin C) all display the same genetic oddity (mutation of a gene known to be essential for the manufacturing of vitamin C) in the same place in the genome. Think about it: that the outcome of the oddity is "non-function" of the gene is not actually central to the reasoning that identifies common descent as the only rational explanation. If the outcome had been the resurrection of a previously-dead pseudogene, the reasoning would have been the same, and it would be equally compelling.

Finally, the claim that the behavior of non-coding DNA elements such as LINEs or Alu elements (which are known to be mobile elements with sophisticated means of translocation) is due to "random biochemical events" is similarly dishonest. While the landing sites of many of these mobile elements are thought to be largely random (with some interesting and subtle exceptions), the process itself is non-random and fairly well understood. In fact, the combination of these two characteristics (largely known modes of mobility plus largely random or unpredictable landing sites) is exactly what establishes common descent as the only rational explanation for many remarkable genomic patterns.

In summary, creationist claims that non-coding DNA is largely functional are ludicrous, and the notion that a presumption of non-function underlies evolutionary explanations of genomic structure is very misleading. Other creationists are fond of this sort of argument, but at RTB they seem to be banking on it. Such misconduct is immeasurably corrosive to RTB's scientific and intellectual integrity, to say nothing of its witness as a public apologetics "ministry." I don't know what else to say.


Anonymous said...

"This claim is irrelevant, at least because the premise is untrue, if not because design proponents would have left the entire bloody genome unstudied while giving lectures and writing books on the impossibility of evolution."

Zing! :-D

Jim Lemire said...

Another excellent post on "Junk DNA".

Randy Stimpson said...

For a software engineer's perspective on junk DNA see Junk DNA is a Myth

Martin LaBar said...

Thanks for citing yourself. I hadn't seen this one, for some reason.