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Comment by bearbin | Hacker News Reader

But this (escape from a vial in a lab) isn't a strong claim, or at least no stronger than the alternative (the virus escaped from bat in a a wet-market)- why is there no outcry against the wet market hypothesis?

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As explained in the linked page under "starting point", the priors for zoonosis are much higher than lab escape. So lab escape actually is a much stronger claim which requires more evidence. The source of the numbers is under the "more >" link.

Zoonosis is basically the null hypothesis, as this is the mechanism for essentially every single other virus. For this virus to be special and have a special and different origin requires evidence.

No, the null hypothesis is unknown origin. Science doesn't just default to either explanation without evidence.

That’s untrue. Null hypotheses are indeed typically “defaults” - for example, assuming, prior to any evidence, that X has no correlation with Y in the population. If you want to put it in a Bayesian framework, scientists cannot avoid priors any more than anybody else.

That's why it would be unknown origin, not zoonosis. They don't default to picking one over the other in the absence of evidence for either.

If you are trying to do a bayesian analysis, you need a prior probability. That is, what it would be expected to be, without your analysis. This would be zoonosis.

There is never absence of evidence for zoonosis, because by association all other viruses came to be via zoonosis. So, before you do any further investigation, it's the default. And then, when you do, zoonosis is already the null hypothesis as it was the most likely before you being your further investigation.

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