Thursday, May 21, 2009

The origin of life

Give me an amoeba and I'll give you a planet teeming with a rich diversity of life. I'll go further, give me a self-replicating molecule -- DNA, for instance -- and I'll give you an amoeba, or something like it.

No big trick. It's inevitable. Replication. Mutation. Natural selection. It would take divine intervention to stop it.

I don't mean to say, of course, that you'd get scarlet tanagers, coral snakes, and Cameron Diaz. No even that you'd get birds, reptiles and mammals. But you'd get something, diverse, complex, and perhaps intelligent.

The trick is getting that first self-replicating molecule.

We know that it happened, and more or less when -- four billion years ago on the primeval Earth. It's not impossible that the seed for terrestrial life came from somewhere else in the universe, but that just moves the riddle to another venue, so we might as well address the question of how might it have happened here.

Many biologists believe that DNA and catalyzing protein enzymes -- the bases for all terrestrial life -- came along after RNA, a self-replicating, self-catalyzing single-strand molecule that can itself be a template for molecular evolution. So how does one start with simple pre-biotic molecules that can be reasonably expected to be present in the early terrestrial environment -- nucleobases, sugars, phosphates -- and get something as complex as RNA. It's a matter of getting these things to join up in the right way, but unfortunately a plausible chemistry for making it happen has eluded researchers for 40 years. Ah, a perfect opportunity for a Designer to step up to the plate.

Not so fast. In the 14 May issue of Nature, chemists from the University of Manchester -- Matthew Powner, Beatrice Gerland and John Sutherland -- offer a pathway for RNA synthesis (the green pathway in the diagram; click to enlarge) that just might break the RNA deadlock. The riddle of the origin of life is not solved, but maybe the solution is in sight.

If there is a lesson here, for the purveyors of creationism and intelligent design, it is that not knowing is not the same as not knowable.