In December 2010, a big story broke: NASA researchers studying a species of bacteria from Lake Mono in California had made a fantastic discovery. The Lake Mono environment is high in arsenic, and the scientists announced they had coaxed a strain of the bacteria into substituting arsenic for phosphorous in its DNA. The implications were staggering: if these results held up, they would be the first evidence of life built on a different blueprint than the standard one, with obvious applications to the hunt for extraterrestrial life. (Phosphorous and arsenic are chemically very similar, lying in the same column of the periodic table. This is part of the reason arsenic is generally toxic to life: it mimics phosphorous in essential biochemical reactions.) I excitedly announced this find in the classes I was teaching, and was thrilled to find that one of the researchers—Felisa Wolfe-Simon—had been a graduate student at Rutgers while I was there. Wolfe-Simon is even friend of a friend, and I suspect I met her at a few graduate student functions.
However, the story fell apart quickly under scrutiny by other researchers. Carl Zimmer summarized the reactions in Slate, and a huge discussion erupted on Twitter under the hashtag #arseniclife, dissecting the results. Another team of scientists led by Rosie Redfield decided to attempt repeating the experiment, suspecting that the NASA group had misinterpreted the data, failing to prove what they claimed they had done. This week, two papers—including the one by Redfield and her collaborators—have pretty much closed the book on the arsenic bacteria. Carmen Drahl, Matt Strassler, John Timmer, and Carl Zimmer all provide some perspective on the new papers, and there are many more analyses out there I haven’t had time to read yet. The narrative is clear: the NASA study had problems with execution and interpretation, the paper was rushed to publication, and the NASA researchers handled both the original announcement and the followup poorly. The new results reveal that the “arsenic bacteria” actually are efficient phosphorous scavengers, surviving in extremely low-phosphorous and high-arsenic environments that would wipe out most other known organisms.
I’m disappointed the bacteria don’t actually metabolize arsenic—it would be awesome to say the least if it were true—but I can’t argue with the new experiments. [Correction: Leonid Kruglyak, one of the coauthors of the new study, informs me that many bacteria do metabolize arsenic. However, they can't substitute it for phosphorous in DNA. My apologies for the error!] Neither can I blame myself for being excited at first: I trusted the media narrative, and my biochemistry background is nonexistent, so I wasn’t able to evaluate the evidence for myself. I should have been more skeptical, I know, since (to quote Carl Sagan, himself drawing on earlier writers) extraordinary claims require extraordinary evidence. However, science doesn’t proceed by accepting what we wish was true, but by the often messy process of testing and retesting claims. That’s why the hunt for the Higgs boson still isn’t over, and why we can still get excited when new observations bear out well-established theories.
My current worry is that, based on some of the interviews and email exchanges with Wolfe-Simon and other authors of the original study, people will continue to assert that arsenic life is real. This is what happened with “cold fusion”, the 1989 announcement from University of Utah physicists Stanley Pons and Martin Fleischmann declaring they had obtained nuclear fusion at room temperatures. Again, this claim was phenomenal: if their results were true, then energy in the future would be inexpensive, clean, and abundant, eliminating the need for fossil fuel consumption forever. However, it was equally obvious the results were far-fetched: nuclear fusion requires overcoming a significant energy barrier, since nuclei are positively charged and repeal each other electrically. Stars achieve fusion through high pressure and temperature, and experiments have found no other reliable way to make it happen; the energy put into making fusion is greater than the energy output in every experiment so far. While I think we’ll figure fusion out someday, cold fusion is too unlikely to be true. Pons and Fleischmann failed to replicate their own results, and nobody else could manage them either. After an initial huge media circus, the cold fusion story died out, leaving just a few isolated people around the world working on it. Robert Park’s book Voodoo Science has a lot more on the story.
I was thinking about all this today because a Facebook friend posted a pro-cold fusion statement on their page. Once again, the promise of cold fusion is hard to deny: who wouldn’t want a cheap, abundant, non-polluting source of energy? The situation was complicated when my friend linked to this 1998 Wired article that basically says cold fusion is plausible and the scientific establishment is being too rigid in rejecting it. To put it mildly, I was frustrated to see that article:Wired is generally a respectable publication, and to see them promoting an idea unsupported by any evidence is annoying. Yes, it’s from 1998, but thanks to the eternal archive of the internet, it survives, lending credibility to an idea that should have died over 20 years ago.
I’m not familiar with the author of the Wired piece, but the article badly misrepresents how science works. Replicability lies at the heart of science: if you can’t reproduce the results of an experiment, something obviously went wrong the first time. Even if your lab repeats an experiment with the same result, but nobody else can replicate it under similar conditions, then either you are delusional or there is a hidden problem. (I exclude deliberate fraud from this discussion, since there’s no reason to suspect it in the cases I’m considering here.) As annoying as it is, experiments don’t prove anything by themselves: they require interpretation and a lot of backup. Just because the researchers are nice people with compelling personal stories doesn’t mean their research is correct.
The problem, as Maggie Koerth-Baker eloquently puts it, is that narrative often trumps science in the public view:
Good science usually makes a bigger deal out of the evidence than it makes out of the story. In fact, that’s actually a problem many legit scientists have—they’re better at talking about the details and data then they are at telling stories. But most of us respond to stories better than we respond to details and data.
(Maggie is referring particularly to crackpot science, drawing on John Timmer’s review of a grand “theory” about planet formation. Go read John’s piece too, while you’re at it.) The details of both the arsenic life and cold fusion stories reveal why they are not trustworthy, but wishful thinking is no substitute for reality.