How Fire Might Have Changed Our Moods https://www.psychologytoday.com/us/blog/how-to-think-like-a-neandertal/202512/how-fire-might-have-changed-our-moods 90% of the body’s serotonin is produced in the gut. Raw diets have a different microbiome than cooked diets. As our ancestors switched to easily digestible foods, they altered the bacterial communities in their guts. These changes likely affected the fermentation processes that produce short-chain fatty acids and regulate inflammation, further affecting serotonin levels. The discovery of fire did more than change the very nature of our food; it changed human behavior. Modern humans, talented but biochemically fragile, may still bear that ancient trade-off in their vulnerability to serotonin imbalances