When our distant ancestors discovered cooking it spurred an evolutionary step forward. Our brains grew larger and our stomachs shrank, and were better able to walk upright.
Cooking food made a big impact because eating raw food is hard work. If you look at other primates they spend much of their life eating.
In 2008 scientists in the UK tried an experiment with humans, putting them in a zoo and feeding them as much raw food as they wanted: berries, fruits, vegetables, etc.
To fulfill their daily energy requirements required eating more than 10 pounds of raw fruits and vegetables — it was taking them most of their day to get through chewing this much food and most were unable to finish their daily ration.
By the end of the two week experiment it was clear that raw foods alone cannot fuel a modern human. All the test subjects lost lots of weight and they couldn’t finish all of their food even though they would eat well into the night… some would have likely died if they had stayed on this diet.