Key points from article :
Bodies of people in the US have been cooling since the 1860s.
Research team collected data on temperature measurements from 1860 until 2017.
Men born in the early 19th century had body temperatures of 0.59°C higher than men today.
Average body temperature today is about 36.6°C, not 37°C as widely thought.
Older people had higher body temperatures than younger people measured in the same year.
