> What's the benefit of the average human body temperature?

It's a balance between preventing infection and not requiring excessive food intake.

> "The number of fungal species that can thrive and therefore infect an animal declines by 6 percent for every 1° C rise in temperature. This means that tens of thousands of fungal species infect reptiles, amphibians and other cold-blooded animals, but only a few hundred harm mammals.".

References:

- "[Mammalian Endothermy Optimally Restricts Fungi and Metabolic Costs][1]", by Aviv Bergman and Arturo Casadevall, DOI: https://doi.org/10.1128/mBio.00212-10  
- "[Fungal virulence, vertebrate endothermy, and dinosaur extinction: is there a connection?][2]" (.PDF), by Arturo Casadevall, DOI: https://doi.org/10.1016/j.fgb.2004.11.008


  [1]: https://mbio.asm.org/content/1/5/e00212-10
  [2]: http://www.aecom.yu.edu/uploadedfiles/casadevall/2005/4.pdf