"What caused the change in colon and intestinal size?......... a shift to more energy-concentrated diets. .......Our shrinking colon size is pretty clear evidence that our bodies started adapting to the energy-dense structure of cooked food and meat, since we no longer had to rely primarily on bulky, super-fibrous plant foods."
Denise MingerFrom:
What is the “Optimal” Diet for Humans? (Part 1) « Raw Food SOS: Troubleshooting on the Raw Food Diet
What is the “Optimal” Diet for Humans? (Part 2) « Raw Food SOS: Troubleshooting on the Raw Food Diet
Extract below:
In part 1 of this “optimal human diet” series, I mentioned that there is no single, exact diet that will deliver perfect health for everyone. We’re tough cookies, us humans—and we only made it as far as we did by adapting to whatever happened to land on our evolutionary dinner plates. Mastodon meat, sweet little figs, plant roots—we made food of it all.
Even so, there’s a notion in the raw food world that we’re still best-suited for the type of diet we ate back in the good ol’ days. You know, before we exited the tropics, conquered all corners of the planet, and invented the deep-fried Krispy Kreme (which surely triggered the downfall of humanity). Maybe you’ve heard claims that we haven’t adapted to cooked food at all, that we’re designed to be vegan or vegetarian, and that our digestive systems still look like those of other fruit-munchin’, leaf-chompin’ primates.
But do those beliefs hold up to reality? Let’s take a look.
Digestive anatomy
There’s no doubt that we have plenty of anatomical similarities with other primates. We do share a good chunk of their genes, after all—especially chimpanzees, bonobos, and orangutans. In fact, some researchers have argued that chimpanzees should be reclassified under the same Homo genus as humans because we’re so similar, although this is pretty controversial and it’s been challenged by more recent research.
All in all, humans have the same general digestive structure as apes: a single-compartment stomach, a small intestine, a cecum and appendix, and a colon. Pretty simple.
But the devil is in the details, as they say. When you look closer, our digestive tracts have some major differences compared to other primates—differences that pose dietary consequences. The most significant is the size of our small intestine versus our colon. In chimpanzees, gorillas, and orangutans, the colon is about two to three times the size of the small intestine. But in humans, those figures are reversed: the small intestine dominates, clocking in at over twice the size of the colon.
A visual representation for your viewing pleasure (humans are the striped bar):
As you can see, there’s not much difference in relative stomach volume—but other primates have a whole lotta’ colon, and we’ve got a whole lotta’ small intestine.
- Taken from “Nutritional Characteristics of Wild Primate Foods” by Katharine Milton, Journal of Nutrition, 1999
So what does that mean?
In simple terms, a big colon is good for handling “low-quality” foods like tough leaves, stems, and fibrous fruits—things that require a lot of digestive work to break down. Primates that eat boatloads of greens, like gorillas, have a whole army of microbes in their colon that digest cellulose and convert it into an energy source. That’s a process called “hind-gut fermentation.” Humans aren’t so lucky; we can digest some forms of fiber, but much of it passes right through us without delivering nutritional value. Our colons aren’t big enough to host enough little organisms to ferment things as effectively as other primates do.
On the flip side, a big small intestine (is that an oxymoron?) is perfect for digesting high-quality foods that are dense, smaller in volume, and easy to break down. That includes soft fruits, animal foods, cooked foods, tender leaves, and perhaps items that have been pre-processed through chopping or grinding. Even our modern-day blended and juiced foods make our small intestines happy, because that pre-processing translates to less digestive work.
In other words, humans are adapted to a softer, more compact diet than other primates. Our bodies have moved away from extremely high-fiber cuisines and are better suited for foods that require less digestive effort.
