The headline is broadly defensible, but the qualifications matter. Effect sizes vary by population, the strongest claims rest on shorter trials, and credible voices push back on how it's typically framed.
There is immense amount of data on the fact that high levels of melatonin in seasonally breeding animals, takes the ovaries from nice and robust ovaries that are capable of deploying eggs and this kind of thing and literally shrinking them and making these animals infertile. These are very high levels of melatonin in seasonal breeders in winter. Melatonin in males of seasonal breeders takes the testes and shrinks them.
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Native comments, Twitter mentions, and Reddit threads about this claim — surfaced together so the conversation isn't fragmented across platforms.
Bookmarking — the dossier-vs-overview split is the right call. Most of the time I want overview; sometimes I want receipts.
Would love a "what would change this verdict" RSS feed. Sign me up if it exists.
Long ago when I was at UC, Berkeley as a master's student, I was working on neuroendocrinology, and we were working on this hamster species of seasonal breeders. And basically when days are long, which inhibits melatonin, these little Siberian hamsters as they're called, have testes about the size of, sort of typical table grapes, although that's a weird way to put it. When days get shorter and the melatonin signal gets longer because light inhibits melatonin, days get shorter, melatonin gets longer. Those same hamsters would have testes that would involute to the size of about a grain of rice.