No one person invented the Paleo diet. The original inventors were the Paleolithic ancestors who survived on it.
In a response to 20th-century industrialization, the diet began taking shape in 1975 with a book published by gastroenterologist Walter Voegtlin called "Stone Age diet".
In 1985 Stanley Boyd Eaton and Melvin Konner published an article in the New England Journal of Medicine advocating for Paleo nutrition.
Today's popularity can be traced to Loren Cordain's 2002 book, "The Paleo Diet", reviving the ancient approach to modern problems.