[cyphar]

Fahrenheit was initially intended to have 96°F be equal to body temperature (in fact it was one of the three fixed points in the temperature scale, designed to have 64 steps between the freezing point of water at 32°F and human body temperature).

However after the introduction of Celcius, Fahrenheit was redefined slightly (with the freezing and boiling point of water being the fixed "nice" values for the scale -- to match the model used by Celcius) which resulted in human body temperature no longer having such a nice value. This also moved the 0°F value. So while technically Fahrenheit does predate Celcius and it did have a "nice" value for body temperature when invented, it was soon afterwards redefined such that arguably the value is just a conversion from Celcius.

In short, you're both correct. :D

[folli]

Why did they come up with 96 instead of 100, a nice round number?

[jcranmer]

Imagine you've just made yourself a thermometer by marking off the 0° and 100° points. Now delineate the 2° intervals, using only the tools you would have had available in the early 18th century.

Now imagine making a thermometer by marking off the 32° and 96° points (64° apart). Now delineate the 2° intervals.

Considering those two tasks, 64 seems a much better number to me (only have to divide unit lengths in half) than 100 (have to divide something by 5).

[folli]

Great explanation, thanks.

[JadeNB]

Sounds like the motivation was powers of 2, not 10.