Several years ago, Dr. Ivan Oransky (MD) and Adam Marcus (MA in science writing) started a blog called Retraction Watch, which reports on scientific papers that have been retracted by the journals that published them or the authors who wrote them. It provides a valuable service to those of us who frequently read the scientific literature, because many journals and authors don’t promote their retractions nearly as much as they promote their papers. Thus, if I want to see whether or not an important publication in the scientific literature has withstood the scrutiny of other scientists, I can check this blog.
Last week, while scanning the new entries, I ran across an interesting one. It reported on a major paper published last year in the journal Nature Chemistry. Despite the fact that it was published only 18 months ago, it has already been cited by 26 other papers in the scientific literature. Why? Because it appeared to solve a very serious problem in what is probably the most popular origin-of-life scenario.
Because the origin-of-life scenario I was taught as fact at university has fallen out of favor among origin-of-life researchers, other scenarios are being explored. One such scenario is the “RNA world” hypothesis. In this view, life was not initially based on DNA. Instead, it was based on a similar molecule, RNA (the differences between the two molecules are shown in the graphic above). This view has garnered a lot of attention, because RNA can do something DNA cannot. It can speed up chemical reactions without being used up in the process.
Why is this important? Many chemical reactions that occur in living systems happen slowly on their own. To be used by a cell, they need to be sped up. Cells do that today with enzymes, and they make those enzymes based on instructions that are found in their DNA. The problem is, of course, that a living system is needed to replicate DNA. But that living system depends on the information stored in DNA. How was DNA originally produced if its very replication is based on the information it contains? The RNA world gets rid of that problem.
Because RNA is very similar to DNA, it can store the genetic information a cell needs to be alive. However, some forms of RNA can also speed up chemical reactions without being used up. In the “RNA world,” then, the first cells carried their information in RNA, and they also used RNA to speed up their chemical reactions. Enzymes and DNA then came later, as these simple living systems began to evolve.
One of the many problems with this origin-of-life scenario is that in all studies so far, RNA needs enzymes in order to replicate properly. Other RNA molecules could, in theory, do the jobs that enzymes are doing now, but no mechanism by which this happens has been found. That’s where the retracted paper comes in. It reports on a series of experiments that seemed to demonstrate a possible way in which RNA could be replicated over and over again without the help of enzymes. However, when another member of the research team (Tivoli Olsen) couldn’t reproduce the results reported in the paper, the team stepped forward to retract it.
What’s interesting is an admission made by the research team’s leader, Nobel Laureate Dr. Jack W. Szostak. He said:
In retrospect, we were totally blinded by our belief [in our findings]…we were not as careful or rigorous as we should have been (and as Tivoli was) in interpreting these experiments.
This happens a lot in science. Scientists aren’t unbiased investigators who don’t have any stake in the outcome of their experiments. Generally, when we do experiments, we are looking for some result. If we aren’t careful, that can make us see things which aren’t really there. In this case, that’s what happened to the authors of the paper.
Now don’t get me wrong. I am not writing about this to insult Dr. Szostak and his team. In fact, I applaud them! Not only did they step up and do the right thing (regardless of the consequences), but Dr. Szostak even freely admitted the reason for the error. I am also not saying that because of this retraction, the “RNA world” hypothesis is wrong. I think it is, but not because of this retraction. Those who really believe that living systems can form as a result of random chemical reactions should continue to investigate the “RNA world” hypothesis, even though I don’t think they will find enough evidence to indicate that it’s a viable mechanism.
I am writing this so that people understand there is no such thing as an unbiased scientist. We all approach science with our inherent biases, and those biases affect our results. The problem isn’t the bias. The problem is that so many scientists (as well as science journalists and science educators) pretend that it doesn’t exist!