“Physiologically, we’re just different from what we were in the past. The environment that we’re living in has changed, including temperatures in our homes, our contact with microorganisms and the food that we have access to. All these things mean that although we think of human beings as if we’re monomorphic and have been the same for all of human evolution, we’re not the same. We’re actually changing physiologically.”
On average, the temperature taken in your rectum or ear may be slightly higher than one that is taken across your forehead or under your arm. When taken in your mouth it will lie between one taken rectally and one under your arm.