Reasons to Believe

Alu Sequences in Primate Genomes: Evidence for Common Descent or Common Design?

If someone had an hour to convince an audience of pastors that humans and chimpanzees evolved from a common ancestor, what evidence would he or she cite?

Last fall, I had the opportunity to witness that very presentation.

I was one of the plenary speakers at the Vibrant Dance of Faith and Science Symposium. This conference was designed to promote informed, non-confrontational dialogue among advocates of the differing Christian perspectives along the creation-evolution spectrum (such as intelligent design, progressive creationism, and evolutionary creationism).

During the opening day’s plenary session, biologist Darrel Falk, president of the BioLogos Foundation, presented a case for evolutionary creationism (formerly known as theistic evolution). Specifically, Dr. Falk argued that humans and chimpanzees must have evolved from a common ancestor because of the Alu sequences found in human and chimpanzee genomes.

Alu Sequences and the Case for Biological Evolution

Alu sequences are highly repetitive sequences of DNA about 300 genetic letters (base pairs, bp) in length and belong to a class of DNA known as SINEs (short interspersed nuclear elements). Alu sequences are unique to primates. There are over 1 million Alu elements in the human genome, making up about 11 percent of the genetic material. Evolutionary biologists, like Falk, point out that humans and chimps share large numbers of Alu sequences in common, with identical (or nearly identical) sequences that occur in corresponding locations in both genomes.

Evolutionary biologists have long thought of Alu sequences as junk DNA. For evolutionists, this clearly indicates that these organisms shared a common ancestor. They believe the shared Alu elements arose prior to the time humans and chimps diverged from their shared evolutionary ancestor. This prompted evolutionists to ask why a Creator, if one existed, would purposely introduce nonfunctional, junk DNA at the exact location in the genomes of both humans and chimps.

Alu Sequences Have Function

Over the last few years, researchers have come to discover that SINE sequences have function. (See my books Who Was Adam? and The Cell’s Design for a more extensive discussion on the functional importance of SINE sequences.)

Researchers from the University of Rochester recently discovered that Alu sequences in particular prevent the overproduction of proteins by breaking down messenger RNA.1

Once produced, messenger RNA (mRNA) molecules direct protein production. If left unchecked, mRNA will continue producing proteins beyond the necessary amounts required by the cell. One strategy cells use to avoid protein overproduction is to breakdown mRNA molecules after it produces the appropriate amount of proteins. As it turns out, Alu sequences play a role in mRNA degradation by working with long non-coding RNA (lncRNA) molecules, also once thought to be useless junk.

Some mRNA molecules possess Alu sequences near one of the molecule’s ends. These Alu sequences can pair with Alu sequences in lncRNAs to form a duplex with the two RNA molecules. This duplex is targeted by a protein called STAU1, which binds to RNA duplexes and destroys them. As a consequence of this destruction, protein production is kept in balance.

Discoveries like this one undermine the case for common descent and human evolution made by evolutionary creationists like Falk. The fact that Alu sequences have function means their presence in primate genomes can be reasonably explained as the work of a Creator. It also means that the identical Alu sequences, which appear in corresponding locations in the human and chimpanzee genomes, can be understood as the use of a common design by a Creator.

Researchers are uncovering more and more examples of junk DNA’s functional importance. In light of this ongoing advance, it’s becoming harder and harder to maintain that genomes are riddled with useless vestiges of the evolutionary process. Instead, it is becoming increasingly apparent that genomes are elegant, sophisticated systems worthy of a Creator.

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

Endnotes:

  1. Chenguang Gong and Lynne E. Marquat, “lncRNAs Transactivate STAU1-Mediated mRNA Decay by Duplexing with 3’ UTRs via Alu Elements,” Nature 470 (February 10, 2011): 284–88.