As a bitter winter storm rages on the East Coast, it’s hard to knock being warm-blooded. But what about the metabolic cost of maintaining a high body temperature? Well, a new study finds that we and many other mammals keep up such a torrid temp because it’s a Goldilocks situation—98.6 is just right.

Albert Einstein College of Medicine researchers previously showed that every one degree Celsius rise in body temperature wards off about 6 percent more fungal species. So tens of thousands of fungi can infect reptiles and amphibians, but we can only be invaded by a few hundred fungi.

In the new work, the researchers created a mathematical model that weighed the fungal protection benefits versus the metabolic cost of high body temperature. And the optimal temperature was 98.1, quite close to what evolution figured out. The research was published in the open-access journal mBio. [Aviv Bergman and Arturo Casadevall, "Mammalian Endothermy Optimally Restricts Fungi and Metabolic Costs"]

Too low a temperature and we’re far more susceptible to fungal infections. Too high a temperature and we’d spend all our time taking in fuel to burn. So 98.6, like that middle bowl of porridge, is just right.

—Steve Mirsky

[The above text is an exact transcript of this podcast.]