Transcript: Paleopoo: What We Can Learn from Fossilized Feces
In the U.S., we tend to get less than 20 grams of fiber a day, only about half the minimum recommended intake. But in populations where many of our deadliest diseases are practically unknown, such as rural China and rural Africa, they’re eating huge amounts of whole plant foods, up to a 100 grams of fiber a day or more, which is what it’s estimated our Paleolithic ancestors were getting based on dietary analyses of modern-day primitive hunter-gatherer tribes and by analyzing coprolites, human fossilized feces. In other words, paleopoop.
These most intimate of ancient human artifacts were often ignored or discarded during many previous archaeological excavations, but careful study of materials painstakingly recovered from human paleofeces says a lot about what ancient human dietary practices were like, given their incredibly high content of fiber, undigested plant remains. Such study strongly suggests that for over 99% of our existence as a distinct species, our gastrointestinal tract has been exposed to the selective pressures exerted by a fiber-filled diet of whole plant foods. So, for millions of years before the first stone tools and evidence of butchering, our ancestors were eating plants. But what kind of plants?
One way you can tell if animals are natural folivores or frugivores is to map the area of absorptive mucosa in their gut versus their functional body size. Folivores are those meant to eat mostly foliage—leaves, while frugivores are better designed to eat fruit. The faunivores, another name for carnivores, eat the fauna.
If you chart animals this way, they fall along distinctive lines. So, where do humans land? Here’s our functional body size, and here’s our absorptive area. So, while eating our greens is important, it appears the natural dietary status of the human species is primarily that of a fruit-eater.
Why does it matter how much fiber we used to eat? Well, one theory for the rising levels of obesity in Western populations is that the body’s mechanisms for controlling appetite evolved to match how many plants we used to eat. Our ancestors ate so many plant foods we were getting like 100 grams of fiber a day; so, for millions of years, food equaled fiber. So, no surprise one of the physiological mechanisms our body evolved to suppress our appetite involved this fiber.
For example, fiber is metabolized by our gut flora into short-chain fatty acids, which bind to and activate receptors on the surface of our cells that alter our metabolism, for example, activating receptors on fat cells to increase the expression of the weight-reducing hormone, leptin. Other hormones are affected as well. Since until recently, food meant fiber, an increase in food intake meant an increase in fiber intake, which made our gut bacteria so happy they made lots of short chain fatty acids, which activated the cell-surface receptors that released a bunch of hormones that made us lose our appetite and down regulated hunger. So, we ate less. But if we ate less, there’s less fiber in our gut; so, less of those hormones were released, boosting our appetite; we got hungry and wanted to eat. But what if food doesn’t equal fiber, like on the standard American diet? Then, we just keep getting these signals to eat, eat, and eat. We’re always hungry. If we haven’t eaten our 100 grams of fiber for the day, our body may be like, “What? Are we starving here?”
Discovering this mechanism makes the food and pharmaceutical industries very excited. They figure they can now come up with new drugs in the fight against the current obesity onslaught. Or, we could just eat as nature intended.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.
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