Jeremiah Tolbert

Word has leaked that today’s press con­fer­ence is about bac­te­ria with DNA that uses arsenic in place of phos­pho­rus in the struc­ture of its DNA.  NASA is fram­ing this has hav­ing broad impli­ca­tions for the search for extrater­res­trial life, but I am won­der­ing about the evo­lu­tion­ary his­tory of such a critter.

Is there an entire par­al­lel evo­lu­tion­ary his­tory, entire groups of species, that have evolved for bil­lions of years to uti­lize arsenic?  Or is this a more rel­a­tively mod­ern tech­nique.   Because it’s not as Earth-​​shattering if these guys turn out to be descen­dants of reg­u­lar DNA struc­ture crit­ters (I’m at a loss for good ter­mi­nol­ogy here.  They’re not arsenic-“based”—they’re still using car­bon as far as I know.)  The impli­ca­tions on the search for extrater­res­trial life is not so great if they still had to evolve under sim­i­lar cir­cum­stances, and this is just a case of reg­u­lar,  store-​​brand life adapt­ing to toxic envi­ron­ments like Mono Lake.  By which I mean, if the con­di­tions were always toxic, it’s pos­si­ble that these bac­te­ria would have never had a chance to evolve in the first place.

Of course, there’s another option to them hav­ing evolved from reg­u­lar DNA-​​based life or even in con­junc­tion over mil­lions and bil­lions of years.  That is, they’re not earth-​​based in ori­gin.  Alien invaders, liv­ing among us!  I sus­pect the early buzz would have an entirely dif­fer­ent tone if that were con­clu­sively the case however.

We’ll learn more at the press con­fer­ence today, I’m sure, and I’m sure they’ve thought through every­thing I’ve just went over.  I look for­ward to more details.  It’s pretty damned excit­ing stuff, but for me it’s just a con­fir­ma­tion of a gen­eral sus­pi­cion, which is that if it’s chem­i­cally pos­si­ble and con­du­sive to self-​​replication, organ­isms will find a way.  The process of evo­lu­tion is like open­ing 10,000 doors simultaneously—I sup­pose it’s inevitable that some of those doors, when not fatally trapped, will lead to some odd places.

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