system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is the unit circle divided into increments of 90 degrees (90, 180, 270, 360) and not based on 100?

I'm just genuinely curious as to why we separate it like that?

For example, 100 degrees would be the same as 90 based on 100 system and 400 degrees would be 360.
gpt
The Sumerians started with a base 6 numbering system. They studied circles for things like navigation and came up with 36 degrees for a circle (in base six, 36 is 100). Later the Greeks decided they wanted more degrees, but found the divisibly of 36 useful.  Since they lacked the decimal point, they chose to make a circle 360 degrees. 

The divisibility remains useful and that's how we all learned it, so it remains.