The Timing of Evolutionary Transitions Suggests Intelligent Life Is Rare

Great article, quite recent. I’m not sure why Christian media aren’t talking more about it:

From the abstract:

The emergence of intelligent life late in Earth’s lifetime is thought to be evidence for a handful of rare evolutionary transitions, but the timing of other evolutionary transitions in the fossil record is yet to be analyzed in a similar framework. Using a simplified Bayesian model that combines uninformative priors and the timing of evolutionary transitions, we demonstrate that expected evolutionary transition times likely exceed the lifetime of Earth, perhaps by many orders of magnitude. Our results corroborate the original argument suggested by Brandon Carter that intelligent life in the Universe is exceptionally rare, assuming that intelligent life elsewhere requires analogous evolutionary transitions. Arriving at the opposite conclusion would require exceptionally conservative priors, evidence for much earlier transitions, multiple instances of transitions, or an alternative model that can explain why evolutionary transitions took hundreds of millions of years without appealing to rare chance events.

I was not impressed with the logic of the paper. As I understand it, the logic is this: because we can only be asking about intelligent life if intelligent life successfully evolved on earth, earth provides a very biased estimate of how likely intelligence is to evolve (i.e. ascertainment bias). It therefore tells us little about how rapidly intelligence might typically evolve; in Bayesian terms, the observation does not change the prior much. And if you start with a very broad prior, you’ll end up with a posterior distribution of how long intelligence takes that is also very broad. So there are really only two contributors to the conclusion: the one observation of intelligence doesn’t tell us much about how easily it evolves, and there are a lot more long times than short times.

In other words, the conclusion that intelligence typically takes a long time to evolve is based largely on the assumption that intelligence typically takes a long time to evolve.

3 Likes

@IsraelP
In other words, it is very dubious to draw conclusions which are statistical in nature when you only have a sample size of 1.

As soon as it could rain, there was life. Here we are. All over our infinitesimal universe. Go play with the Drake Equation. The article is analogous to all forms of creationist denial of evolution. It ignores the rational fact that we are utterly insignificant at every scale. But we’ll never know empirically, so they can get away with spouting such specious ‘Bayesian’ nonsense for forever. As can all the religious fanatics without.

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