Imagine youre the first guy in your tribe to discover temperature and make a termometer. You can measure temperature of people now. You notice a pattern: most people have a temperature around 37C. But a few have a temperature of 40+C, and they soon die. You discover that being above 40C is a good predictive factor for death this week. You give a name to this condition: hyperthermia.

You also notice that the ice makes things colder. You have to trek all the way to the mountaintop to get it down to your savannah, but its worth checking if it can