"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.