On this blog post over at Greg Laden’s, I’ve made a damn fine effort (if I do say so myself) at explaining the process of scientific inquiry to a pair of commenters who’ve taken issue with the idea that anyone could know anything about the event of abiogenesis — the “Origin of Life”, when the fuzzy boundary between chemicals and life was first breached — that happened on this planet. I’ve agreed with them on a number of points, including Anthony’s main thesis, that there was exactly one way that this universe’s past has unfolded, exactly one “truth” to any event in history, and that as a result, figuring out that exact truth is nearly impossible short of having been there to witness it yourself. He accuses the current scientific establishment of “decadence” (belittling our blog friend DuWayne in the process), and of “ideological materialism” wherein the elite of the scientific world are beholden to assume materialism lest their entire epistemology crumbles beneath them.
Luckily, science doesn’t work that way or we’d have stopped investigating this universe long ago.
The scientific method can be implemented to attempt to model events that it cannot prove with 100% certainty happened in exactly one way. By learning about the past, through the physical and inferential evidence we have available to us, we can develop hypotheses which are testable today. If our hypotheses about the past are correct, we can then correctly predict the results of these experiments, and if the experiments are carefully enough crafted, they can disprove the hypotheses and force us to start over. In the specific case of the abiogenesis event that occurred on this planet, we might never know the exact formula that resulted in our exact lineage. This should not stop us from taking the evidence we have available to us, the direct and inferential physical evidence that shows how this planet was very likely composed chemically in the early pre-biotic environment, and extrapolating from that knowledge that perhaps self-arranging lipids and amino acids might have formed.
The Miller-Urey experiment in 1953 took some of our best guesses about the pre-biotic environment and attempted to verify the Oparin-Haldane hypothesis that it would allow for amino acids to self-arrange. When the experiment was complete, they were proven correct. Amino acids — the building blocks to life itself — formed spontaneously, without direction, in an environment that was like science’s contemporary understanding of the early Earth. If this experiment had failed, it would have put a nail in the coffin of the abiogenesis theory, though not the last one, certainly. The fact that it succeeded suggests one of two things: 1) amino acids might spontaneously emerge in a number of environments, or 2) we got lucky and hit upon the correct way to create amino acids but did not replicate the early Earth, thus disproving abiogenesis. The former is far more likely, for obvious reasons — not ideology, but pure math. If there are a near infinite set of environments that the planet could have had, then there are a near infinite set of environments to test. The problem comes down to one of narrowing — if we know the early Earth had to have ammonia (to provide the organic compounds necessary), then we’ve excised all models that do not include ammonia. Scientists later discovered a photochemical reaction of nitrogen that would provide this ur-Earth with the necessary ammonia. Meanwhile, we narrow our options down significantly with each new piece of evidence.
The fact that better evidence turned up suggesting that the early environment was actually significantly different from the conditions replicated in the Miller-Urey experiment should thus hardly come as a surprise, though the actual early environment is still hotly debated among scientists. Miller tried again in 1983 with the newer data, but came up empty — hardly any amino acids to be found. However, Professor Jeffrey Bada repeated the experiment with an even better approximation of the early environment, e.g. that Miller’s second test had omitted iron and carbonate, and amino acids were once more formed spontaneously through nothing more than pure chemical interactions in the simulated environment. And that certainly isn’t the only such related test.
Two different environments, both resulting in amino acids. Certainly the later test benefits from the extra evidence collected about the early Earth, but getting amino acids in multiple different environments bodes well for our ability to show that every step in the grand staircase toward biology is plausible. We know that the lipid bilayer necessary to create a cell membrane can self-arrange as an emergent property of the lipid’s intrinsic hydrophobia (fear of water) on one side, hydrophilia on the other. They’ll form up all by themselves without prompting, given the right environment. So will RNA nucleotides, meaning if the RNA-world hypothesis is correct, we’re well within our rights to suggest that the hypothesis is the one that best fits the available evidence and make further predictions and experiments from there.
None of this is, you’ll notice, an attempt at building a narrative of “how things definitely happened”. People will often demand such a thing, knowing that they cannot themselves replicate experiment results, nor comprehend their interconnectedness with other such experiments if they’re even aware of these other experiments, nor suss out how all the pieces of the puzzle ultimately fit together. I understand this drive — the drive to build a narrative that is easily digested — because every human being has it. It is that drive that frees up one’s mind to contemplate other things, like immediate survival concerns or reproduction or the pursuit of leisure. It is that drive that one combats when arguing with people who cling tenaciously to their received dogmas. The temptation is great to replace one dogmatic narrative with another. But the scientific worldview demands that we understand that our understanding of this universe may never reach 100% certainty about any single topic or event, but as we slowly polish and chip away at the theories we have built, we can bring them to within impressive degrees of certainty that put any former, more dogmatic, effort at explaining the universe to shame.
The level of certainty that Andrew believes we are expressing about the study of abiogenesis is galling, and his repeated insistence that scientists are engaging in myth-making betrays his lack of understanding of the process. That we don’t know a great many things about the actual abiogenesis event on this planet means nothing, ultimately, in the study of how it might have happened. It is like asking that we know everything about the daily life of the very first ape to climb down out of the trees, or else the theory of evolution is about building a just-so narrative. I’m personally content to allow the process of scientific investigation to grind down all the possibilities until there are but a few left, and we can choose which one fits all the evidence best, until such time that new evidence overturns the model and we are forced to revisit.
That’s how science works, you see. And science does indeed work.
(To within a reasonable degree of confidence.)