In the opening scene a scientist argues once the ambient temperature of some region is 37°C we'll all get eaten by fungus. It will evolve to live at body temperature.

There are some precedents for this: hibernating bats lower their body temperature to that of a moldy environment, and are getting infected with a fungus which kills 90% of them in some cases [2]. Logic goes that raising the ambient temperature could be the same (with some evolution thrown in) as lowering our body temperature.

Is it credible? No idea, not that kind of scientist.

[1]: https://www.youtube.com/watch?v=OLNagvJHl3g

[2]: https://en.wikipedia.org/wiki/White-nose_syndrome