Divergence of Copy: Evolution Reversed in the Media

By Jeff Goodenbour | 1.29.07

Universities and research institutions often distribute press releases in conjunction with major journal articles authored by their scientists, particularly when the articles concern buzzword topics such as evolution, love, human nature, the big bang, and so on. A select few of these press releases catch the eye of an editor and even fewer work their way into the media, where they may be transformed into a report that bears more or less resemblance to the findings described in the original publication. In the worst cases, these lucky press releases end up as mangled, sensationalized, or fantasized communiqués devoid of the real scientific consequence of the original journal article. One thing you can almost always count on, however, is a gripping, sensational, and totally inaccurate headline.

One recent such travesty led off a recent BBC article. The headline was: “Evolution reversed in mice,” and the article was a summary of findings published in the journal Developmental Cell. In what followed, the general public was treated to a terse description of a somewhat complicated process in which a pair of University of Utah professors utilized the similarity of two critical developmental genes to reconstruct an ancestral genetic sequence.

The headline itself is enticing - it brings to mind big razor teeth, increased musculature, probably even some nasty claws. Prehistoric mice had to handle sabretooth tigers after all, not your modern day tabby. The article is in fact accompanied by a photo of a somewhat bizarre-looking, contorted mouse, its midsection depressed and eyes closed – perhaps prehistoric mice saw through their eyelids and had relatively massive upper bodies! Sounds reasonable!

But rather than focusing on some kind of Flintstones rodent, the article’s true stars are actually the two genes: “Hoxa1, which controls embryonic brain development, and Hoxb1, which plays a key role in the development of nerve cells that control facial expressions in animals.” This somewhat wordy description is correct: the two genes are both involved in nerve development (although it may lead you to believe that brain and nerve development are in fact quite disparate, when they are essentially the same process). These two genes are very closely related in sequence and function, and descended from a single “parent” gene called Hox1.

The remainder of the article gives a very vague and cursory description of the actual experiments, concluding with the rather blah punchline, “the hybrid gene is not completely identical to the ancient one, but the scientists say it performs essentially the same functions.” Oh, so they didn’t hop in a time machine and collect ancient Hox1 sequence information after all? And why should we care if this mysterious “hybrid gene” does the exact same thing as the natural genes? A quote from Mario Capecchi, one of the study’s authors, at least hints that there’s an interesting nugget to be found here: “It gives a real example of how evolution works because we can reverse it.” Really, that’s inspirational and all, but do you think maybe we deserve to know a little bit of exactly what the hell it is that’s going on? Or does the general reader not deserve any detail beyond a rehash of the press release’s eye-catching, but ultimately meaningless, hook?

One dirty little secret that mass-media science news articles generally omit: genes, the discrete units which code for the proteins that perform most biological functions, are controlled by a number of switches, technically referred to as promoters, enhancers, or repressors. A minority of genes are constitutively active, meaning that they are always on. Most, however, are at the whim and whimsy of their particular switches, which are often activated by other gene products. Those genes in turn have their own control elements and so on and so on (nobody ever said genetics was simple). Thus, it is not only what the genes themselves code for, but also when, where, and why the genes are turned on that produces the visible intricacies of life.

Another dirty little secret is that many genes aren’t particularly unique; one of the critical processes of evolution is duplication. In some cases, this copy-and-pasting happens to entire genomes (some plants have hundreds of chromosomes as a result), while in others it occurs within one confined region or individual gene. Theoretically, this duplication creates a “backup” for evolution, similar to an external hard drive on a computer: with redundant copies, one becomes expendable to mutation. Should one break down because of mutation, no big deal, we’ve got another copy. Should something positive come about, well, that’s icing on the cake.

Hoxa1 and Hoxb1, the particular foci of this study, are prime examples of both of these dirty little secrets. The thrust of this work was to investigate the two closely related genes and their corresponding control elements, attempting to determine the basis for the slight differences between them. By first showing that the protein coding sequences for these genes are mostly interchangeable, they proved that the real differences responsible for the genes’ disparate functions are differences in their control elements. Over the course of evolution each gene was left with only one of two ancestral regulators. The divergence in gene control enabled the genes to be used for different functions. It’s very similar to what happens when NFL teams draft athletic college quarterbacks such as Antawn Randle-El, Matt Jones, or Seneca Wallace: they find themselves with two quarterbacks, but one does the job better. So rather than waste talent on the bench, these players see time as receivers and make the occasional play (and occasionally the Super Bowl-turning play at that). One quarterback or gene carries the typical duties while the other gives the playbook some options.

After developing an understanding of how the gene works the researchers experimentally “turned back the clock” by making a hybrid gene with both of the ancestral control elements. Mice with the reconstructed Hox1 gene were then observed to be physically and behaviorally similar to mice with the two contemporary genes. Big deal, right? Actually, yes. The experimental results imply a delicate interaction of functionality and selection causing divergence in repeated sequences. To an extent they have provided a counterpoint to the argument from “irreducible complexity” that is the darling of the Intelligent Design movement: that biological systems are too complex to have evolved piecemeal (and therefore must have been created all at once). Reconstruction of this functional gene shows that two unique genes that have subtly distinct roles today have likely evolved their specific functions from an original gene with its own utility.

This is the take-home message that the BBC should be offering the public, not some science-fiction “reversing evolution!” claptrap. The public is unlikely to understand, appreciate, and accept many scientific theories, particularly evolution, if they are consistently packaged in such simplistic terms. Joe Nonscientist should be becoming Joe Moderately-literate-about-what’s-going-on-inside-him by reading articles that don’t condescend by omitting key features of the original research. It’s difficult enough for people to filter through all the misinformation about evolution promulgated by the Bush advisors, fundamentalists, Doverites, and Kansans, without having to deal with the BBC superficially regurgitating the neon fallacies of PR hooks.