Reasons to Believe

Junk DNA Hotspots Have Evolutionary Biologists Singing the Blues

I love listening to live blues music. One of my favorite venues is the Canyon Club in Agoura Hills, CA, about an hour and a half drive from my house. Discovering the Canyon Club, one of the premier hotspots for the blues in Southern California, has afforded me the pleasure of seeing legends like Johnny Winter, John Mayall (the father of the British blues), and Charlie Musselwhite play.

In the realm of biology, a team of researchers has recently discovered hotspots in the genome of the water flea Daphnia pulex. Unfortunately for evolutionary biologists, this finding is forcing them to change their tune about the origin of introns (regions of noncoding DNA within genes). At the same time it has creationists and intelligent design proponents making joyful sounds. That’s because this discovery helps provide an explanation from a creation perspective for genome features considered “junk” DNA, supposedly the most compelling evidence for biological evolution.

According to evolutionary biologists, junk DNA results when undirected biochemical processes and random physicochemical events transform a functional DNA segment into a useless molecular artifact. Pieces of junk DNA remain as part of an organism’s genome solely because of their attachment to functional DNA. In this way, the supposed junk persists from generation to generation.

Evolutionists also highlight the fact that in many instances identical (or nearly identical) segments of junk DNA appear in a wide range of related organisms. Frequently the identical junk DNA segments reside in corresponding locations in these genomes. Because evolutionary biologists think the events that produce junk DNA are rare and random, the existence of shared junk DNA sequences makes sense only if these organisms arose from a common ancestor. As such, the junk segments emerged prior to the time when the organisms diverged from their shared evolutionary ancestor. After all, why would a Creator purposely introduce nonfunctional, junk DNA at the exact location in the genomes of different, but seemingly related, organisms?

Over the last five years or so, scientific advancement has provided a partial answer to this question. As detailed in both The Cell’s Design and Who Was Adam? biologists have discovered that many classes of junk DNA have function. (Go here and here to read a few representative articles on the functional importance of junk DNA.) The recognition that junk DNA possesses utility weakens the argument for biological evolution and common descent. It may also explain why identical sequences occur in corresponding regions of the genomes of related organisms. Location may be critical for proper operation.

But what about the junk DNA sequences that do not currently appear to play useful roles? Do these sequence elements, which may be true genetic junk, provide evidence for common descent, and, consequently, for biological evolution? How else can they be explained?

It turns out that the origin of junk DNA sequences may not be random or rare. Researchers from Indiana University and the University of New Hampshire have been studying the origin of introns. These pieces of DNA—considered to be junk—interrupt genes and must be removed, or spliced out, before the information in the gene can be used by the cell’s machinery to make proteins. Life scientists have long thought insertion of new introns into genes was a rare occurrence because the effects are almost always deleterious.

To everyone’s surprise, the research team learned that intron insertion events in the water flea genome seem to be much more frequent than anticipated. Even more shocking: introns appear to have been inserted repeatedly into the same locations in different genomes sampled from several populations of water fleas. In other words, the researchers discovered that there are hotspots for intron insertions in the water flea genome. The origins of these junk DNA sequences are frequent and repeatable. According to Michael Lynch, one of the authors of the study, “Remarkably, we have found many cases of parallel intron gains at essentially the same sites in independent genotypes. This strongly argues against the common assumption that when two species share introns at the same site, it is always due to inheritance from a common ancestor.”

At this point, it isn’t clear how many species display repeated, parallel intron insertion events. It’s reasonable to expect that this would be a widespread phenomenon. This result also opens up the possibility that some classes of junk DNA may be genuine junk, yet reflect not common ancestry but reproducible, nonrandom biochemical events. Biochemists have known for years that mutations frequently occur in nonrandom fashion at hotspots. It is only reasonable to expect that other types of junk DNA exhibit a nonrandom genesis as well.

Why do different organisms possess identical junk DNA sequences at corresponding locations within their genomes? From a creation model standpoint, the response to this question appears to have two facets. One relates to the functional usefulness of junk DNA sequence elements designed by the Creator. The other acknowledges that some sequences of junk DNA truly are garbage originating through natural process. But the discovery of insertion hotspots for introns and the possibility that other junk DNA sequences may arise by repeatable, nonrandom mechanisms means that these shared sequences do not reflect common ancestry, but reproducible biochemical events.

Based on recent advancements, one of the best arguments for evolution finds itself at a crossroads. Take it away, Johnny Guitar!

Subjects: Junk DNA

Dr. Fazale Rana

In 1999, I left my position in R&D at a Fortune 500 company to join Reasons to Believe because I felt the most important thing I could do as a scientist is to communicate to skeptics and believers alike the powerful scientific evidence—evidence that is being uncovered day after day—for God’s existence and the reliability of Scripture. Read more about Dr. Fazale Rana