Here’s Dr. Greger talking about fiber:
I pulled out that chart he included from this study…
Studying the Human Gut Microbiota in the Trans-Omics Era – Focus on Metagenomics and Metabonomics, Current Pharmaceutical Design, 2009
… that shows our fiber intake from Paleolithic times to present:
Greger: “We’ve been eating 100 grams of fiber every day for millions of years.” That’s a lot! I can’t imagine eating that much fiber. I think I do better than that 12-18 grams of most Americans though, because everything I eat is a plant. Only plants provides fiber.