Commenting on our review, Nelson writes that “extensive cohort studies indicate that [body temperature] is closer to 36.5°C” than 37°C. The review indeed specified that “normal human core body averages about 37°C,” and that “there is a superimposed circadian rhythm with roughly a 1°C range.” “Normal core body temperature thus varies from ≈36.5°C (usually about 3:00 am) to ≈37.5°C (usually about 3:00 pm). In premenopausal women, there are also superimposed changes in temperature with the menstrual cycle, with core temperature being about 0.5°C greater during the luteal phase.”

Nelson cites two studies to support an average core temperature of 36.5°C. In one of them, Gurven et al. present a cohort study in which average core temperature somewhat implausibly decreased ~0.5°C over just 16 yr. However, about a third of the way through, temperature...

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