First the biologists disabled the catalytic system, without which the bacteria cannot move. Then they introduced variants of the chosen bacterial protein, thioredoxin, into isolated bacterial colonies. "To the researchers' surprise, a mutant carrying only two amino acid changes..., restored the ability of the bacteria to move."

On this website we have adocated experiments that could demonstrate the sustainable creation of new genetic programs in closed systems. Therefore, we carefully studied this report and commentaries on it. Yes, we grant that the right two amino acid substitutions might plausibly occur by random mutation in nature. And this small change apparently caused the bacteria's thioredoxin to acquire a different catalytic function.

However, the new metabolic pathway was not randomly found by desperate bacteria, but designed by the experimenters. Furthermore, the key to it, the succesful variant of thioredoxin, was selected by the bacteria only after the experimenters carefully installed it. After all that, the process only restored a capability previously posessed by the bacteria. Most importantly, darwinian constructive mutation cannot be demonstrated by the existence of a single, carefully staged increment. By searching diligently one may discover, for example, a typographical error that makes sense; this fact does not demonstrate that uncontrolled typos can generate lengthy new sentences. (They can't.)

The darwinian tenet that pointwise mutations on existing genetic programs can create new genetic programs in a sustainable manner remains, to us, undemonstrated. We urge anyone who's interested to read the full report in Science. We invite informed comments.

We welcome this elaboration on pseudo-panspermia by two veteran astrobiologists. Of course, we believe the chirality in meteorites derives from past life on their parent bodies.

While it is exciting to elaborate on the big bang, it is wrong to pretend that a theory so fluid has sufficient authority to govern unrelated fields like biology. Obviously, the big bang theory does not confirm that life can originate from nonlife by natural means. Only real evidence could do that.

• "Genome sequences reveal that a deluge of DNA from organelles has constantly been bombarding the nucleus since the origin of organelles.... at frequencies that were previously unimaginable.
• "Phylogenetic analyses and genome comparisons show that influx of organellar DNA to the nucleus has had a marked quantitative impact on the gene content of eukaryotic chromosomes.
• "Translocated genes might be expressed to provide products that are targeted to all parts of the cell.
• "This mechanism of natural variation is unique to eukaryotic cells and was an important force in the genesis of eukaryotic genomes."

Jeremy N. Timmis, Michael A. Ayliffe, Chun Y. Huang and William Martin, "Endosymbiotic Gene Transfer: Organelle Genomes Forge Eukaryotic Chromosomes" [

Max Wallis

Wallis suggests that cometary debris, before the impact, brought microorganisms that introduced the the exotic amino acids into the biosphere. Then, newly arrived or newly evolved microorganisms employing them caused epidemics against which most native species were defenseless. At the same time, other newly introduced genetic material may have prompted an ensuing radiation of new species that were not susceptible to the epidemics.

After ruling out "a series of substance classes such as minerals, metals (like iron), or pure carbon in any of its phase states," Krueger et al. determine that the dust is most likely "polymers of derivatives of the the quinone type, such as quinoline-quinones." Interestingly, one of these quinones would neatly explain a puzzling feature of the UV spectra of interstellar dust: the "hump" at 218 nanometers corresponds precisely to the main peak of o-dihydroquinone. [Thanks, Daniel Fischer.]

We think that the presence of complex organic polymers in interstellar dust strengthens the case for life out there.