As we all know, we have an innate dislike of bitter foods. This has evolved in us since in ancestral times where bitter tastes were an indicator of poisonous substances and avoiding them was key to our survival. So much so that we are sensitive to bitter taste in solutions that are 0.008 times as concentrated as salty or sweet solutions.
Despite this scientifically rational dislike there are people (and even communities) who claim to like bitter foods such as karela. In Bengali cuisine, for example, the first course or the appetizer course is predominated by bitter tasting dishes such as uchche charchari and shukto.
One of the reasons that struck me as underlying this preference is in the preparations that are eaten of these vegetables like bitter gourd. Bitter gourd, before being cooked is generally rubbed with salt and then squeezed to remove the bitterness (even by people who claim to like it!)I know of a lot of people who like karela chips that do taste bitter. It is just that they are fried and laden with calories, something the human body also has an evolved preference for. In uchche charchari, rice and ghee are added to the bitter gourd which are carbohydrates and fats that our body needs whereas shukto has other vegetables and spices that we have learned to have a preference for.
So to get the nutrients we need, we have come up with ways of getting over the limitations of the substances we can get this from and making them more appealing to us. This in essence is where I guess cooking started from.