‘Normal’ body temperature varies from person to person by age, time of day, where it’s measured, and even menstrual cycle. External conditions also influence your thermometer reading.
The fossilised skull of an Odontocyclops displays its pineal foramen.
Nkansahrexford (Own work) via Wikimedia Commons
Mammals’ ancestors had a third eye and the fossil record of its disappearance tells us the story of the evolution of one of our most important features: warm blood.