XP Is a System that fills up in a XP Bar that shows your DNA On The Right.
You gain EXP by eating food or by living 1 in-game year, the amount of bonus xp you get for your age is the number divided by 5 rounded down like the DNA risk calculation.
The Base number of XP you get from 1 in-game year starts at 10 There are also bonus XP added for Grazer And Jaws for eating the specific type of food.