Monday, July 21, 2008

Book Review: "The Human Diet: Its Origins and Evolution"

I recently read this book after discovering it on another health site. It's a compilation of chapters written by several researchers in the fields of comparative biology, paleontology, archaeology and zoology. It's sometimes used as a textbook.

I've learned some interesting things, but overall it was pretty disappointing. The format is disjointed, with no logical flow between chapters. I also would not call it comprehensive, which is one of the things I look for in a textbook.
Here are some of the interesting points:
  • Humans in industrial societies are the only mammals to commonly develop hypertension, and are the only free-living primates to become overweight.
  • The adoption of grains as a primary source of calories correlated with a major decrease in stature, decrease in oral health, decrease in bone density, and other problems. This is true for wheat, rice, corn and other grains.
  • Cranial capacity has also declined 11% since the late paleolithic, correlating with a decrease in the consumption of animal foods and an increase in grains.
  • According to carbon isotope ratios of teeth, corn did not play a major role in the diet of native Americans until 800 AD. Over 15% of the teeth of post-corn South American cultures showed tooth decay, compared with less than 5% for pre-corn cultures (many of which were already agricultural, just not eating corn).
  • Childhood mortality seems to be similar among hunter-gatherers and non-industrial agriculturists and pastoralists.
  • Women may have played a key role in food procurement through foraging. This is illustrated by a group of modern hunter-gatherers called the Hadza. While men most often hunt, which supplies important nutrients intermittently, women provide a steady stream of calories by foraging for tubers.
  • We have probably been eating starchy tubers for between 1.5 and 2 million years, which precedes our species. Around that time, digging tools, (controversial) evidence of controlled fire and changes in digestive anatomy all point to use of tubers and cooked food in general. Tubers make sense because they are a source of calories that is much more easily exploited than wild grains in most places.
  • Our trajectory as a species has been to consume a diet with more calories per unit fiber. As compared to chimps, who eat leaves and fruit all day and thus eat a lot of fiber to get enough calories, our species and its recent ancestors ate a diet much lower in fiber.
  • Homo sapiens has always eaten meat.
The downside is that some chapters have a distinct low-fat slant. One chapter attempted to determine the optimal diet for humans by comparing ours to the diets of wild chimps and other primates. Of course, we eat more fat than a chimp, but I don't think that gets us anywhere. Especially since one of our closest relatives, the neanderthal, was practically a carnivore.
They consider the diet composition of modern hunter-gatherers that eat low-fat diets, but don't include data on others with high-fat diets like the Inuit.


There's some good information in the book, if you're willing to dig through a lot of esoteric data on the isotope ratios of extinct hominids and that sort of thing.

9 comments:

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reid said...

In terms of the majority of the world's population, I wonder if the human diet might be considered to be "devolving".

Stephan said...

Reid,

From a health perspective, I think that's accurate.

Debs said...

That's surprising and interesting about corn's insignificant role in Native American diet prior to 800 AD. Do you know if that's the latest introduction of grain in any region subsisting (traditionally) on a grain-based diet? I would guess so, based on what I know of rice and wheat.

As to Reid's comment, I think the human diet is devolving right alongside the human capacity to take care of our world and ourselves in other ways. We're out of touch with what's healthy and sustainable, and diet's a large part of that trend.

Debs
Food Is Love

Drs. Cynthia and David said...

This reminds me of a TV show about healthy diets where they made overweight volunteers eat enormous amounts of raw vegetables and fruits, modeled after the "ape" diet. The volunteers lost weight of course and their blood lipids decreased, while running constantly to the toilet facilities. They might have been better off just fasting, since humans don't have the digestive tract for this kind of diet.

Stephan said...

Debs,

I believe corn was the last major grain to become widespread. There are still a number of S American groups that never really adopted corn historically, so it depends on the population.

Stephan said...

Cynthia and David,

Interesting. In the short term, I think a diet like that could improve health because it eliminates the big culprits in the modern diet. It's not sustainable though, because we aren't equipped for it, as you said.

Dr. B G said...

I think it's fascinating that you mention the reduction in cranial size of humans...(esp since you are studying neurobio!) have you heard of 'epi genes'?

Our gene expression may in fact be handed down to our progeny -- as protection/defense for survival I would conjecture. Millions of years of 'honing' of our genes created a lot of 'nonsense' non-usable 'coding' but maybe not...

Perhaps, de-evolution is possible as well... without crucial nutrients like fats, cholesterol (since everyone and now the inclusion of obese/high LDL-children, takes statins which may excessively block steroid/chol synthesis), adequate protein and vitamins/minerals... can we be passing along legacies of metabolic derangements to future generations??

Have you seen W*A*L*L*E the movie yet? It casts an ominous light on the future of mankind (no Crossfitters or primal-diet followers apparently survived!) *ha*

-G

Stephan said...

Hi G,

Yes, I'm familiar with epigenetics. Price was interested in it (although the word probably didn't exist in his day). He claimed that the effects of poor nutrition can last generations. I'm always keeping my eyes peeled for data about it. There's no doubt that some traits can be passed down epigenetically. It wouldn't surprise me if they could affect health.