Yeah, I know it seems strange. But the hetero and homogametic sexes have swapped in other lineages, such as amphibians, so it is within the realm of plausibility. Boas/pythons are a more ancient lineage...it's possible that the ancestral state is female ZZ and male ZW, and that as the sex chromosomes diverged in other lineages, there was a switch between the homo/heterogametic sexes. I just struggle to find another explanation that is scientifically plausible yet explains all the observations the way that this one does.
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