Our 37 degrees Celsius body temperature is just warm enough to ward off fungal infection and obviate the need for snacking, says a study.

“One of the mysteries about humans and other advanced mammals has been why they are so hot compared to other animals,” said study co-author Arturo Casadevall, professor and head of microbiology and immunology at Albert Einstein College of Medicine in the U.S., reports the journal mBio.

The research builds upon earlier work by Casadevall showing that the number of fungal species that can thrive and therefore infect an animal declines by six per cent for every 1 degree Celsius rise in temperature, according to an Einstein statement.

This means that tens of thousands of fungal species infect reptiles, amphibians and other cold-blooded animals, but only a few hundred harm mammals.

Such protection against fungal infection, Casadevall has speculated, could have been crucial for the triumph of mammals following the age of dinosaurs.

Casadevall and his Einstein co-author Aviv Bergman, professor of computational biology, devised a maths model that analysed the benefits gained by body temperatures that protect against fungi versus the costs (in terms of extra food consumption or snacking) required to maintain body temperatures between 30 degrees and 40 degrees Celsius.

The optimal temperature for maximising benefits while minimising costs was found to be 36.7 degrees Celsius, which closely approximates normal body temperature of 37 degrees Celsius.

“This study is a good example of how mammalian evolution has been driven by both external biological factors and internal physiological constraints,” Bergman said.

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