Paleo Diet Reading List

Reading about human origins can be fascinating, and informative.  It has been said that nothing in biology makes sense except in light of evolution, and the same could be applied to diet. I originally wanted to understand the physiological biochemistry of digestion, but several textbooks later I had lots of facts but very little understanding.  While strolling at the zoo, I realized I needed textbooks that described the differences between animal digestion -- a comparative physiology textbook, perhaps.  But again, after reading all of the most popular titles, I had only scattered facts and no theory of the differences between human and animal digestion, or even between carnivore, omnivore, and vegetarian modes of sustenance.

Luckily, two Harvard professors have written books on human evolution with particular emphasis on how dietary changes made us human.  In the process, they provide the best, although somewhat contradictory, source of information on comparative dietary physiology.  Daniel Lieberman's The Story of the Human Body (2013) is a more traditional telling of human evolution, but it is written in an attempt to answer the question of how our paleo bodies have adapted (or not) to modern lifestyles.  Richard Wrangham's Catching Fire: How Cooking Made Us Human (2009), is an extended argument concerning the importance of cooking to human evolution, but he does deal extensively with the comparative behavior and anatomy of humans, proto-humans, chimps, and other primates.  Only at the end of his book does he tackle the problem of modern dietary choices for humans, and then only as a parting shot.  John Hawkes, at the University of Wisconsin, is often mentioned as an authority on human evolution, and I would include his Great Courses lecture (2011) in this triumvirate of human evolutionary tales.

The above works often reference modern accounts of extant hunter-gatherer tribes to understand what life might have been like during the Paleolithic era.  The most notable of these books are Lee's account of the !Kung San, and I would also suggest Weston A. Price's classic Nutrition and Physical Degeneration: A Comparison of Primitive and Modern Diet and their Effects.  A modern synthesis and review of the same subject matter can be found in Lindeberg (2009).

It is interesting to compare the literature on human evolution with the diet book literature making use of ideas in human evolution.  The originator of the "Paleo Diet", Loren Cordain has several books specifying his interpretation of the evidence.  While his 2002 book specifies a diet that seems more restrictive than what I've read in Lieberman and Wrangham, I haven't had a chance to read his 2012 book yet.

1. Lieberman D. The Story of the Human Body: Evolution, Health, and Disease. Knopf Doubleday Publishing Group; 2013.
2. Wrangham R. Catching Fire: How Cooking Made Us Human. Profile Books; 2009.
3. Price W. Nutrition and Physical Degeneration: A Comparison of Primitive and Modern Diets and Their Effects (Hardback). Benediction Classics; 2010.
4. Lindeberg S. Food and Western Disease: Health and Nutrition from an Evolutionary Perspective. Wiley; 2009.
5. Lee RB. The !Kung San: Men, Women and Work in a Foraging Society. Cambridge University Press; 1979.
6. Cordain L, Friel J. The Paleo Diet for Athletes: The Ancient Nutritional Formula for Peak Athletic Performance. Rodale; 2012.
7. Cordain L. The Paleo Diet: Lose Weight and Get Healthy by Eating the Food You Were Designed to Eat. J. Wiley; 2002.

Paleolithic Nutrition compared to Modern American Diet

From: Lieberman D. The Story of the Human Body: Evolution, Health, and Disease. Knopf Doubleday Publishing Group; 2013.

What Do Carnivores Dream About?

Anyone with a house cat already knows the simple truth of a new study on the comparative physiology of sleep across mammals. Carnivores sleep much more than would be expected compared to herbivores and omnivores:

Carnivores:

Herbivores:

Omnivores:

Of course, these data don't answer the original question, but only raise more questions.

This website uses the data to conclude that humans should eat a vegetarian diet, because human sleep requirements match those on the Herbivore sleep regression, and we don't get as much sleep as other omnivores of the same body weight.  But based on discussion in The Story of the Human Body: Evolution, Health, and Disease by Daniel E. Lieberman humans in their modern form -- i.e. that would be recognizable as human today -- cooked their food, which consisted of vegetables and meat and fish.  None of the other animals in this study cook their food.  Perhaps our higher quality diet allows us to spend less time digesting and more time alert?

But herbivores spend very little time asleep!  In fact, from this data, one might conclude that a limit on the size of herbivores is the number of hours in a day.... the largest herbivores spend almost the entire day (and much of the night) awake and, probably, eating.  In contrast, carnivores sleep the most, presumably because they can satisfy their nutritional requirements with less time and effort.

Why don't humans sleep more?

Paleo Diet

Over the last million years a group of primates began walking upright. This genus, Homo, (our species, Homo sapiens sapiens, evolved about 200,000 years ago) is distinguished by a number of physiological and morphological adaptations to their environment.   Importantly, a change in diet from our primate relatives appears to have been the key change that drove our recent evolution.

What was the paleo diet of the genus Homo?

Stephan Guyunet provides this analysis:

"All we know is that they ate some meat. Although humans eventually became top-level predators, we also don't know whether these early humans were actively hunting, or simply scavenging what other predators left behind-- perhaps using their tools to access gristle, brain, and marrow inaccessible to other animals.

At the same time as tool-marked bones appear in the archaeological record, early humans began undergoing a remarkable physical transformation, which represented (in large part) a progressive genetic adaptation to a new subsistence strategy. Our brain doubled in volume, our gut became smaller, and the proportion of small intestine to large intestine increased. Our teeth and jaws became smaller and less robust (Daniel Lieberman. The Story of the Human Body. 2013).

What does this signify? The consensus is that these changes occurred in response to a shift toward a so-called "high-quality" diet. This means a diet that has a higher calorie density and contains less fiber, relative to the typical primate diet of leaves and low-calorie fruit (the latter is not at all suitable for a modern human). The small intestine is what breaks down and absorbs protein, carbohydrate, and fat, while the large intestine ferments fiber to extract calories from it. The shift from a large-intestine-dominant gut to a small-intestine-dominant gut signifies a shift from getting most calories from intestinal fiber fermentation, to getting most calories from direct absorption of protein, carbohydrate, and fat."

Antinutrients in Wheat

Grains don't want to be eaten.  As Dr. George Diggs makes clear in his youtube video, plants protect their leaves from herbivores and their seeds from seed-eaters with a whole range of chemical defenses.  In the case of seeds like wheat, there are multiple lines of defense, any one of which should give a thoughtful eater pause.  In combination, these defenses indicate that wheat should not be eaten by humans.

This is a much stronger argument than saying that some humans are gluten-intolerant or gluten-sensitive.  While gluten can be hard to digest for some people and has been identified as the causative agent in Celiac Disease, it is only one of an array of antinutrient compounds found in wheat.

Source: Scientific American, Surprises from Celiac Disease

• Wheat Germ Agglutinin (WGA) binds to cells in the intestine and can cause the gut to leak and create inflammation in the immune system.1,2,3,5
• Wheat Amylase Trypsin Inhibitors may fuel inflammation and immune reactions. 4
• Gliadin, a compound that specifically increases intestinal permeability, an idea first popularized as "leaky gut syndrome".6,7,8

Caveats: not all of these compounds are harmful to everyone, preparation (e.g. cooking) can destroy some toxins like WGA, and 'the dose makes the poison', so low doses of these antinutrients should have less effect than large doses.  But the fact remains that wheat is not a perfect food.  It increases inflammation, and in susceptible individuals provides the necessary and sufficient conditions for developoing autoimmunity, arthritis, diabetes, etc.

Gliadin is particularly worrisome because of its ability to 'tear holes in the gut'.  Gliadin (a component of gluten) mimics cholera toxins that can unlock the tight junctions sealing intestinal cells to one another.  Without intact junctions between the cells, open holes in the gut lining open are large enough to allow undigested food into the body.  These chunks of food have been detected using genetic testing and observed in animal studies (cite paper found WGA bound to everything).

Source: Scientific American, Surprises from Celiac Disease

This is not just a problem for people with Celiac's disease or gluten sensitivity. Wheat's gliadens have the same effect in everyone; they increase inflammation load (your body has to clean up everything that spilled into your blood after you ate wheat), and they provide the exposure of your immune system to foreign compounds which may trigger autoimmune conditions such as M.S., arthritis, diabetes, etc.  This topic is discussed in depth in this interview with Dr. Alessio Fasano, the researcher who discovered how wheat mimics cholera toxins to break down intestinal epithelium.

Sources
1.van Buul, V. J. & Brouns, F. J. P. H. Health effects of wheat lectins: A review. Journal of Cereal Science 59, 112–117 (2014).
2.Catassi, C. et al. Non-Celiac Gluten Sensitivity: The New Frontier of Gluten Related Disorders. Nutrients 5, 3839–3853 (2013).
3.Sollid, L. M. & Jabri, B. Triggers and drivers of autoimmunity: lessons from coeliac disease. Nat Rev Immunol 13, 294–302 (2013).
4.de Punder, K. & Pruimboom, L. The Dietary Intake of Wheat and other Cereal Grains and Their Role in Inflammation. Nutrients 5, 771–787 (2013).
5.Junker, Y. et al. Wheat amylase trypsin inhibitors drive intestinal inflammation via activation of toll-like receptor 4. J Exp Med 209, 2395–2408 (2012).
6.Pellegrina, C. D. et al. Effects of wheat germ agglutinin on human gastrointestinal epithelium: Insights from an experimental model of immune/epithelial cell interaction. Toxicology and Applied Pharmacology 237, 146–153 (2009).
7.Pusztai, A. et al. Antinutritive effects of wheat-germ agglutinin and other N-acetylglucosamine-specific lectins. British Journal of Nutrition 70, 313–321 (1993).
8. Fasano, Alessio, et al. "Zonulin, a newly discovered modulator of intestinal permeability, and its expression in coeliac disease." The Lancet 355.9214 (2000): 1518-1519.

Pleistocene Climate Change Context

A roadmap of the last 50,000 years helps put the modern global warming in context:

This awesome graph, and many others, can be found here. Includes a good discussion of the Eemian interglacial and other interglacials in comparison with the modern Holocene.

Climate Crunch

Deconstructing Conclusions

During the winter of 2009-2010 I began investigating climate science, and since then have been reading in the field on-and-off. Again this last winter I have been reading way too much, trying to get to the bottom of various intricacies of the coupled earth-human system. Suffice to say, the Earth's climate is extremely complex, and every scientific sub-discipline has made its own peace with the devil in the details. Getting to the bottom of what scientists believe, and why, is no easy task, and after more than a year of research I have learned a huge amount about the Earth, but still am not definitively convinced about every aspect of climate change science.

This is as it should be. Science is complex and ever-evolving, and the Earth is a very, very complicated place. But provisional results and untested assumptions, although ever-present, make soft bedrock for climate policy. The truth is that we simply do not understand many of the key issues, such as feedbacks, in the climate system.

Many issues, such as divergence in tree-ring proxy records, don't by themselves discredit the theory of anthropogenic global warming, even if scientists can't explain everything. But they do begin to cast doubts. The issue of "hide the decline" probably falls into this category, because although some scientists chose to substitute instrument data for the misbehaving paleo data, the divergance can be explained. But is this explanation just hand-waving? How do we really know what happened hundreds or thousands of years ago? Obviously climate proxies may be complicated, idiosyncratic, and only reliable under certain conditions. It has been said that "trees are not thermometers," but this admission, even if carefully defined, can lead to increasing skepticism.

Unresolved Issues

Skeptic Science (SkS) has a great index of skeptic arguments, many of which continue to be problematic. They attempt to "refute" each argument, and they are the best source for good answers to most of these issues. But not every question can be answered definitively. Sometimes one question simply leads to three or four more. For example, they point out that warming is not due to the sun....but it is very, very, complicated. SkS explains why CO2 lags temperature in paleoclimate....but their response is not good system thinking, doesn't address the skeptic arguments about what the Vostok ice core means, and isn't especially convincing.

I've been researching climate change for over a year, and still am not close to understanding many of the major issues. What's worse, I can't find good evidence that the climate scientists understand all of the issues either! Much of science is dependent on good faith and trust, but at some point an explanation has to be convincing. Some theories (and I would put String Theory and Global Warming into this category) are too gnarly to be comprehended by mere mortals. They may be true, but I can't believe in what I don't understand.

The bottom line is that, if you really want to know,... its complicated. I'm officially revoking my previous conclusion, pending better explanations of the science. Maybe I'll have to wait to believe the models until they're proved true: until then I'll continue to entertain belief in multiple possibilities about this weird, beautiful world we live on.

More Paleoclimate Links:

NASA Climate Monitoring

NOAA paleoclimate

A History of Paleoclimatology

The Magical North Central Texas that Used To Be

North Central Texas is composed of three major ecosystems, the Cross Timbers, Black Prairie, and Fort Worth Prarie. Less than 150 years ago, sparkling streams were abundant with trout, perch, and catfish...and alligators! Indeed, Kendall (1845) found alligators along the San Gabriel in the southern Blackland Prairie as "too plentiful for any useful purposes." Black bear were also common, along with mountain lion. Brooke (1848) reports gray wolves as far east as McLennan County, ocelot in bottoms of Brazos River near Waco in McLennan County. The last jaguar record was a large male killed in Mills County (Lampasas Cut Plain) in 1903.

Other vanished creaturs out of this Noah's Ark world include river otter, ringtail (a cat-like creature), badger, javalina (collared peccary), bison, pronghorn antelope, turkeys, and prarie chickens. Many of these animals still persist in zoos or mountains out west, but some cannot be found anywhere on the planet. For example, both the ivorybilled woodpecker and the carolina parakeet, once found near modern day Dallas/Ft. Worth, are extinct.

Estimates of the destruction of the Blackland Prairie ecosystem range from 98% (Hatch et al 1990) to 99% (Riskind and Collins 1975) to more than 99.9% (Burleson 1993). Some of the last remnants can still be seen at the Nature Conservancy's Clymer Meadow Preserve. Slightly more Fort Worth Prarie and Cross Timbers survive. Dyksterhuis (1946) studied relics of the Fort Worth Prairie, and, surprisingly, Cross Timbers are still one of the largest relatively unaltered forest vegetation types in the eastern United States (Stahle &Hehr 1984), but there are more in Oklahoma, for example, Pontotoc Ridge Preserve. Examples of old-growth Cross Timbers forests in North Texas are found in Comanche County (Leon River), Tarrant County (Fort Worth Nature Center), and Throckmorton County (Nichols Ranch).

Prairie remnants are threatened by eastern red cedar (Juniperus virginiana) and cedar elm (Ulmus crassifolia) because of a lack of natural fire. Results include reduction in broad-leaved plants and increased abundance of grasses. (Diamond & Meins 1993). Over much of the slope-lands, as muich as three feet of soil have been eroded, exposing barren rock where once was prairie soil (Hayward &Yelderman 1991). So, although remnants remain, they are often degraded by various human activities such as heavy grazing or selective cutting and their authenticity is rarely noticed or protected.....I wonder how many people realize what used to be?

Much of this text, and the image, are from Shinner's and Mahler's Illustrated Flora of North Central Texas, published by Botanical Research Institute of Texas.

More great info about Texas Native Plants, from the Plant Resources Center at UT - Austin.