As I’m watching The Daily Show and The Colbert Report, there are seemingly endless commercials for Ben Stein’s creationist movie, Expelled. In the commercial, Stein is a student in a classroom where his instructor tells the students that evolution is unguided and undesigned. “How did life begin in the first place, dude?” Stein whines in his trademark monotone. This question is supposed to be terrifying to his professor--so terrifying that Stein is, you know, expelled.
It’s not like we have no idea. There are many competing hypotheses that attempt to explain the origin of life. Although scientists don’t necessarily agree on what it means to be alive, there is agreement that living organisms arose from non-living material in a long, slow process—there was no single moment when the first cell “sprang to life.” Hypotheses about the origin of life, collectively called abiogenesis, differ on which component of living cells arose first. Some postulate that some sort of cellular membrane had to arise first. Others suggest that self-replicating genetic molecules must have formed as the initial step toward life. One of the most widely cited hypotheses is the RNA-world idea, which says that short segments of RNA similar to modern ribozymes were the first components of cells to arise. Ribozymes are bits of RNA that are just large enough to self-replicate and to catalyze simple metabolic reactions. Another category of abiogenesis hypothesis proposes that simple metabolic pathways were the first step toward life. One particularly attractive hypothesis suggests that the reverse citric acid cycle was the original metabolic pathway and would have used ambient energy, perhaps from volcanic vents, to assemble the organic chemicals needed for life to begin.
The short answer to Stein’s question is that we don’t know how life began. However, this doesn’t mean that a supernatural explanation is necessary. The question of the origin of life is not scary to real scientists. The “intelligent design” idea that Stein endorses answers every question with “God did it.” From a scientific point of view, this is no answer at all.