There is a lot of information out there that suggest fiber really causes a lot of irritation in the bowel movements. Then we have the Massai Warriors who lived on meat, milk, and blood. They weren't getting any fiber at all and didn't suffer. This just one of many civilizations that thrived on no fiber.
In my experience fiber really irritates my gut and bowels. Increased fat, more moderate protein, and fermented foods do wonders.