The microorganisms aren’t quite what most people imagine when they hear “aliens,” especially since the life-forms are from earth. But the organisms can use arsenic to function in place of phosphorus, a biological ability both novel and, well, alien to life as we know it—or, rather, knew it.
The bacteria did not use arsenic naturally.
The bacterium was found in California’s strange Mono Lake, a chemically abnormal lake home that has higher-than-normal levels of arsenic. Although arsenic is chemically similar to phosphorus, an element long thought to be crucial for life, arsenic is usually toxic. Nonetheless, researchers have speculated that arsenic-based life might exist on earth, arguing that if so, it would force a major revision in our ideas about what basic elements life requires.
In this case, the bacteria did not use arsenic naturally, but instead adapted to use it in a laboratory setting as researchers increased the level of arsenic in its diet. Eventually, the bacteria began using the arsenic as a normal part of their metabolic and cellular processes—whereas most organisms would have died. Still, the bacteria reportedly “thrived best” on a phosphorus diet.
In that sense, although the discovery of a life-form that can live on arsenic is fascinating, it falls short of predictions that we might find a “shadow biosphere” of life-forms based on arsenic that (allegedly) evolved separately from phosphorus-based life. Arizona State University astrobiologist Paul Davies, one of the scientists behind the research, explained, “At the moment we have no idea if life is just a freak, bizarre accident which is confined to earth or whether it is a natural part of a fundamentally biofriendly universe in which life pops up wherever there are earth-like conditions.” He added candidly, “Although it is fashionable to support the latter view, we have zero evidence in favour of it.”
So while some may see in the discovery more evidence that “aliens” may be out there (albeit genuine extraterrestrials), it in fact offers less evidence for the possibility of a unique form of life than some scientists had hoped for. Further, learning that life can live on a slightly different chemical cocktail does nothing to show that life of any sort can evolve; the two are distinct questions. Finally, and as we pointed out previously, given that the evolutionary origin of life is a dubious speculation (for creationists) and not well understood problem (for evolutionists), positing a separate form of life that evolved independently would raise more questions than it would answer and only cast further doubt on the evolutionary enterprise.
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