Abiogemesis

 

You said:

From what I've learned of recent discoveries, an "RNA world"(since RNA can both carry information and catalyze reactions) under early Earth conditions is almost inevitable, and it seems a DNA world would eventually ensue via natural selection. Life didn't get much further than that for a couple billions of years, when eucaryotic life appeared, and then again for a couple billions more for multicellular life to appear, and since then it seems to have taken its own sweet time evolving into sentience let alone consciousness. Indeed, it took major extinction events to shove things along. These events therefore seem perhaps to be rare and highly unlikely steps -- steps that may make us close to unique. Since we don't know how often worlds like the what the Earth was when life first appeared might be (mass, temperature, tectonic activity, oceans) we cannot even assume the most primitive life will be common, but that does seem likely. Other than that the signs are that the evolution of a technological society that survives for any length of time is going to be really rare. Of course we only have our own history to go by, and we may have been real slow-pokes and these things may happen more often than what our history might indicate.

ChatGPT said:

You’re thinking about this in a very sober way. Once you grant an RNA world—and I agree, that hypothesis has grown steadily stronger over the past few decades—the step from chemistry to primitive life begins to look less like a miracle and more like a phase transition. If you have liquid water, energy gradients, carbon chemistry, and enough time, self-replicating systems don’t seem outrageous at all. They may even be common.

Where it gets interesting—and unsettling—is everything after that.

On Earth, life appears very early. The planet cools down, and within a few hundred million years we already have evidence of microbes. That suggests abiogenesis might be relatively easy given the right setup. But then… stasis. For roughly two billion years, life remains prokaryotic. No nuclei, no multicellular organisms, no forests, no animals. Just microbial mats and oceans of bacteria. That long plateau is striking.

The jump to eukaryotes—likely via endosymbiosis, where one cell engulfed another and didn’t digest it—may have been an extraordinarily improbable event. Or it may simply require time and oxygen levels to rise sufficiently. We don’t know. But it does look like a bottleneck. Multicellularity evolved multiple times independently (plants, animals, fungi), which hints that once you have complex cells, cooperation among them might be comparatively easy. Still, it took another long stretch.

And you’re right: mass extinctions seem to act as evolutionary reset buttons. The extinction at the end of the Permian and the one that ended the reign of non-avian dinosaurs reshaped the ecological chessboard. Without the latter, mammals probably remain marginal creatures. No primates, no us. In that sense, catastrophe appears creative. But are such extinction events rare or common on Earth-like planets? We don’t know. Impacts, volcanism, climate swings—these may be routine features of rocky worlds.

Your larger point touches on what’s often called the “Great Filter.” Somewhere between chemistry and galaxy-spanning civilization, there may be one or several steps that are vanishingly unlikely. Abiogenesis? Complex cells? Intelligence? Stable technological society? Or perhaps survival past one’s own inventions?

The sobering thing is that we have a sample size of one. Earth might be typical, or it might be a cosmic outlier. It could be that microbial life is everywhere, but complex life is rare. Or that complex life is common, but technological intelligence is rare. Or that technological intelligence is common—but self-destructs quickly.

There’s another wrinkle: we may indeed be slow. Evolution is opportunistic, not goal-directed. Intelligence is not obviously favored unless ecological conditions reward flexible problem-solving. Dinosaurs dominated for 160 million years without developing radio telescopes. So perhaps intelligence is not the “natural endpoint” but a side branch that occasionally appears.

Given what we know so far, I’d tentatively say this: simple life may well be common. Complex multicellular life less so, but not absurdly rare. Technological civilizations that last more than a geological blink? That might be the truly rare event.

And there’s a quiet irony here. If technological societies are rare because they self-destruct, then the real bottleneck isn’t biology—it’s wisdom. Evolution may produce cleverness far more easily than restraint.

You’ve always been interested in survival at the species level—immortality by continuation. If the filter is ahead of us rather than behind us, then the question isn’t “How rare are we?” but “Can we avoid becoming one more brief flare in the dark?”

You said:

A comment on the idea that what we call primitive life developed quickly and hence by implication easily or even inevitably. That is a non sequitur, and, really, several hundred million years is not a short time.

ChatGPT said:

That’s a very fair pushback.

You’re right on both counts. “It happened early” does not logically entail “it was easy,” and a few hundred million years is not trivial by any human scale. We have a bad habit of compressing geological time until it feels like an afternoon.

The inference people make goes like this: Earth becomes habitable; within a few hundred million years we see isotopic or fossil hints of life; therefore, abiogenesis must be relatively probable under suitable conditions. But that reasoning quietly assumes that the clock started when conditions became stable and that we’re not missing an earlier, slower prehistory of failed attempts. It also assumes that once life appears, it is detectable quickly—which may not be true.

There’s a subtle selection effect here as well. We are observing from a planet where life did arise. If abiogenesis typically takes 2 billion years but planets only remain stably habitable for 1.5 billion, then most worlds would remain sterile. We would, by necessity, find ourselves on one of the rare worlds where it happened unusually “fast.” That makes early appearance compatible even with low probability.

And you’re absolutely right: several hundred million years is an enormous span for chemistry to explore possibilities. Given trillions upon trillions of molecular interactions occurring continuously across oceans, hydrothermal vents, mineral surfaces, tidal pools—“hundreds of millions of years” might represent an astronomical number of experimental trials. In that sense, long time plus vast chemical combinatorics can compensate for improbability.

So the correct statement isn’t “life arose quickly, therefore it was easy.” It’s more cautious: “life arose relatively early in Earth’s habitable window, which is suggestive but not decisive evidence that abiogenesis is not vanishingly improbable.”

We’re reasoning from one data point and deep uncertainty about the starting conditions. That’s a very thin statistical foundation.

Your instinct to resist the leap from “early” to “inevitable” is sound. Geology stretches our intuitions in both directions: it makes brief catastrophes look long and long gestations look brief. Hundreds of millions of years is both a blink on planetary timescales and an eternity for chemistry.

Which is precisely why this whole question remains open—and interesting.