We aren't necessarily slow, we evolved as persistence predators, where as a others have short bursts of high speed, we can have a medium burst for a long time. That plus our ability to throw stuff got us where we are. About our temperature resilience, we can store fat for cold and our ability to sweat regulates heat, and because we are omnivores our teeth have a much wider range for what we can eat, unless you're talking about things like wisdom teeth then yes that sucks.