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> If true, and complex life evolved more than once on the same planet, then it is much less likely as a strong candidate for the great filter [1]. The hard ste
by Qem 2y ago
> If true, and complex life evolved more than once on the same planet, then it is much less likely as a strong candidate for the great filter [1].
The hard step was not complexification of life. It was long-term atmospheric oxygenation. It took two attempts, the first one short-lived, and between 3-4 billion years to finally succeed for good.
- marcosdumay 2y agoI vote on abiogenesis. But yeah, oxygenation is a good candidate. Anyway we don't have that much of certainty about how it happened exactly.
- Qem 2y agoIt's not necessary to assume a single hard step to explain the rarity of intelligent life. Considerations about the late appearance of a technological civilization on Earth point to between five and six hard steps from origin of life to us. Abiogenesis can account for one, oxygenation for another, and we still need to find another three or four more. See https://arxiv.org/pdf/0711.1985 https://arxiv.org/pdf/0711.1985
- marcosdumay 2y agoThat that paper is one (very good) explanation for the early and sudden appearance of life on Earth, despite it being presumed a rare phenomenon. But there are other possible explanations. About the Great Filter, in principle we can expect the probability of those things to vary by several orders of magnitude, so only one would qualify. All of them being equally unlikely is actually harder to explain than the alternative.
- com 2y agoIt’s too early to say whether it is “for good”, unless you’re talking about atmospheric oxygenisation - that one almost certainly has an end date!
- MattPalmer1086 2y agoOn earth... We don't know what other chemistries might be viable.