Questionable Motives

January 13, 2010

Does mental illness lend support for evolution or creationism?

ARLINGTON – A recent study on the 8 percent of human DNA that is derived from viruses may show a cause of cell mutation and psychiatric disorders such as schizophrenia and mood disorders, according to an article by The University of Texas at Arlington biology professor Cédric Feschotte published in the Jan. 7, 2010, issue of Nature magazine.

The study — led by Professor Keizo Tomonaga at Osaka University in Japan — revealed that the genomes of humans and other mammals contain DNA derived from the insertion of bornaviruses, RNA viruses whose replication takes place in the nucleus of cells. It was the first to show sequences derived from a virus other than retroviruses. Researchers have known since 2001 that 8 percent of human genetic material is derived from retroviruses.

The scientists also were able to recover spontaneous BDV insertions in the chromosomes of human cultured cells persistently infected by BVD.Based on these data, Feschotte proposes that BDV insertions could be a source of mutations in the brain cells of infected individuals.

“These data yield a testable hypothesis for the alleged, but still controversial, causative association of BDV infection with schizophrenia and mood disorders,” Feschotte said. (Source)

Interesting relationship. But what does this have to do with a loving creator?

Steve Novella at NeuroLogica offers us the following commentary:

Creationists don’t like the notion of junk DNA, any more than they like the concept of vestigial organs – the two concepts are closely related. Both imply an evolutionary past. Both also are partly founded upon an argument of exclusion, which they try to present as an argument from ignorance (but there is a subtle difference). An argument from exclusion basically says that we do not know of any function for junk DNA therefore it probably has none. Such arguments are only as good as the extent to which we have searched for a function. After about a century of genetics, and half a century of studying DNA, we have a reasonable level of confidence that much of junk DNA is indeed junk. You cannot prove once and forever a negative claim, but you can get to high levels of confidence.

An argument from ignorance takes the form – we do not know what the function of junk DNA is, therefore it has this specific function (for which there is no positive evidence).

It is also true that over the years we have discovered functions for some of what was previously considered junk DNA, but only a small fraction. This was to be expected. Initially scientists identified the coding regions of DNA – those bits for the parts of genes that directly code for proteins. Near these coding genes were also identified regulatory regions – these determine when and how the gene is expressed. But between these coding and regulatory regions are vast sections of DNA with no apparent function, despite extensive efforts to find one. This is the so-called junk DNA.

But there is also more to our knowledge of junk DNA than just that we cannot find a function for it – such as the identification of viral endogenes and pseudogenes. These are stretches of DNA that not only have no known function but also correspond to known segments of viral RNA. Why would there be a stretch of DNA in the human genome that looks like a bit of a viral gene, but incomplete and apparently non-functioning? This is more than an argument of exclusion. Also – why would it be that the only viral segments we have discovered are from retroviruses and now BVDs?. If you make the argument that the creator is recycling some viral code, why only from those that either place their RNA in animal genomes as part of their lifecycle, or at least replicate in the nucleus and occasionally make some DNA?

But it also gets better, because these viral endogenous DNA segments are not sprinkled at random throughout the animal kingdom – they occur in a pattern consistent with our picture of common descent. In other words, we find the same endogenous viruses in the same locations in related species – in an evolutionary pattern.

We are likely to find more functions, or at least effects, of some of what is now called junk DNA, but not all of it. Nature is resourceful and makes use of what is there, but it is also messy and clutter does not go away unless it provides a significant enough disadvantage to survival. So our DNA is a bit cluttered.

But there is useful information in that junk DNA – it is partly a record of our evolutionary past, and it provides powerful evidence for common descent. In fact, common descent is the only viable explanation for the pattern of endogenous viruses we have discovered in various species. Creationists don’t have a viable alternative scientific hypothesis (just their go-to default untestable explanati0n – goddidit) – they can only take pot shots at the science in order to generate confusion and doubt. That is because creationism is not a science, it is denialism, and confusion and doubt is all they have.


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