“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 — in 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, paleo-poop. 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 — strongly suggesting 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, meaning leaf eaters or fruit eaters, is to map the area of absorptive mucosa
in our 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 eat the fauna,
another name for carnivore. If you chart animals out this way
they fall along distinct 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 acid, 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, activating the cell-surface receptors,
releasing a bunch of hormones that make us lose our appetite and
down regulate hunger, so we eat less. But if we eat less, there’s
less fiber in our gut so less of those hormones are released,
which boosts our appetite, we get hungry and we want to eat. But what if food doesn’t equal fiber,
like on the standard American diet? Then we keep just getting
those signals to eat, eat, 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 the new drugs in the fight against the current obesity onslaught. Or we could just eat as nature intended.