Monday, December 8, 2014

The History of Gut Bugs--Part 3 of 3


Richard Wrangham of Harvard University argues in his book “Catching Fire: How Cooking Made Us Human”[1] “that the invention of cooking—even more than agriculture, the eating of meat, or the advent of tools—is what led to the rise of humanity.”

In his book, he says that the ability to harness fire and cook food allowed the brain to grow and the digestive tract to shrink, giving rise to our ancestor Homo Erectus 1.8 million years ago.

“Cooking is the signature feature of the human diet, and indeed, of human life — but we have no idea why,” says Wrangham,  “It’s the development that underpins many other changes that have made humans so distinct from other species.”

Wrangham surmises that cooking made eating easier and enabled us to get more calories from our food.  This allowed early humans to devote more time to other activities, and aided in  the development of tools, agriculture, and social networks. Wrangham was able to prove that cooking coincided with humans possessing larger brains and bodies and smaller guts, jaws, and teeth—all consistent with eating a diet higher in calories and more tender than earlier foods.

“Cooking is what makes the human diet ‘human,’ and the most logical explanation for the advances in brain and body size over our ape ancestors,” Wrangham says. “It’s hard to imagine the leap to Homo erectus without cooking’s nutritional benefits.”

Wrangham says that cooking had great impacts on families and relationships, making a stable home with cooking facilities a central part of family life.  He writes that:

“Cooking permitted a distribution of labor between men and women: Men entered into relationships to have someone to cook for them, freeing them up for socializing and other pursuits and bolstering their social standing. Women benefited from men’s protection, safeguarding their food from thieves. Humans are the only species in which theft of food is uncommon even when it would be easy.”

One thing that Wrangham did not explore was the impact of cooking on our gut bugs.  As it’s well-established that early humans ate plenty of starchy foods, the manner in which foods were cooked and eaten is important to the development of prebiotics.  When starches are cooked and cooled, retrograded resistant starch is formed.  This specific type of resistant starch plays a large role in the development of beneficial gut microbes[2].  When eaten together with raw starches, the impact is even greater.  Early cooking methods[3] would have definitely favored the formation of retrograded resistant starch[4].  For the first 500,000 or so years, cooking was done by laying foods next to hot fires or on rocks heated in the fire.  Later, earthen ovens and steaming pits were more common, but it is certain that cooking food was time consuming and costly in terms of resources needed.  It is also certain that the advent of cooking foods gave rise to great changes in mankind, but it did not seem to impact the survival of gut microbes or harm them in any way.
An average sized earth oven used to bake lechuguilla* yields relatively little energy relative to the cost. An average person needs to consume 2000 calories per day. But let's assume that that our ancestral forefathers were somewhat smaller and tougher and required only 1500 calories. Even so, a single oven would only feed five people for one day, yet hauling the raw materials, building the oven, and processing the food probably required at least two or three person days worth of effort[5].

            *Lechuguilla is a species of Agave plant.


It’s time for me to back up a few claims I made on this journey through our evolution.  How can I so definitively say that our early ancestors ate loads more prebiotic fiber than we eat today?  Easy, we look at their fossilized feces.

Well-preserved Coprolite

It’s the stuff of jokes and late night comedy skits, but believe it or not, petrified poop—coprolites—can be found all over the world and dated precisely.  When discussing coprolites that are more than 10,000 years old, one thing becomes abundantly clear—this ain’t your grandpa’s crap!  “Paleofeces[6]” as they are commonly called, are more similar to the droppings left behind by raccoons and bears than those of modern day people.  They are filled with bones, scales, hair, seeds, twigs, and undigested starch and pollen granules.  It’s obvious that these remains were left behind by someone who was ‘hongry’. 

Coprolites are found generally in two places; sheltered latrine sites and the insides of mummies.  Some well-preserved paleolithic era mummies have been found that showed they regularly consumed tea made from the Willow tree—presumably as medicine, and also that they were almost all infested with parasites[7].  Also discovered in numerous coprolites from around the world was the widespread consumption of pollen[8]. Analysis of coprolites indicates consumption of flowers from a variety of plants including beeweed, prickly pear, horsetail, cottonwood, squash, and cattail.  Pollen is an excellent source of intestinal microbe food.

The study of coprolites tells us many things about our ancestors.  Besides simply a glance at what was eaten, they give clues to the technology of the day, cooking methods, seasonal eating, and illnesses.  For instance, millet grains were widely consumed 12,000 years ago and the millet’s appearance in coprolites speaks volumes about the way it was harvested and processed[9].  Some millet was found finely crushed and others coarsely ground—the technology for both methods is vastly different.  Also, the appearance of millet chaff and stems gives clues to harvesting methods. 

Some well-preserved 10,000 year old coprolites from the Southwestern United States show us not only the menus of the day, but also pieces together a picture of what meals were like throughout the year.  Three main seasonal staples ruled their diet:

1.      Consisted mainly of prickly pear cladodes or nopales (leaf pads), and was consumed in the late spring. This menu is primarily consumed when other resources were not readily available and may be considered a dependable, though undesirable meal.
2.      Consisted of pit-baked lechuguilla and sotol caudices, or hearts, throughout the Winter. This menu took a lot of work, but provided reliable caloric return.
3.      An a la carte selection of prickly pear fruits, or tunas, during the summer. They were easy to harvest, quite tasty, and a highly desirable meal.
The dietary pattern shows a seasonally variable diet that included undesirable foods during times of scarcity as well as a complete dependence upon desirable foods when they were available.

Another distinguishing characteristic of paleolithic poop is the seeds it contained.  98% of all coprolites that have been discovered in North America contain plant seeds. Among these were seeds from a wide variety of plants:  cactus, walnut, persimmon, hackleberry, mesquite, yucca, grape, and wild onion.  Walnuts of the day were not like the supermarket variety we know—they were small and the meaty insides were hard to extract, no problem for these crafty fellows...they smashed them to bits and ate the pieces—shell and all[10]!  

More proof that modern man probably would not be too happy on a true paleo diet are the common contents of paleo poop such as plant skins of cactus pads and wild onions which were swallowed whole[11].  Animal bones were found in 97% of coprolites examined, some were tiny fish and lizard bones, but many were fairly large[12]!  In one coprolite, a squirrel’s leg bone 1.2” long was found.  Rodent bones were the most common, such as rabbits, rats, and mice.  Almost half the coprolites had hair, skulls, teeth and jaws of mice and rats indicating these critters were eaten whole!  Don’t think for a minute though that these desert dwellers didn’t take advantage of bigger game: evidence that they killed deer, antelope, and wild sheep abounds.  Bones with scrape and teeth marks—not to mention the presence of hunting tools—tell the story that fresh meat was always welcome.

Hind's Cave Human Coprolite Remains

Now, we know exactly what you are thinking—some scientist found one pile of dung with bones and weeds in it and made sweeping statements that this was how everyone lived. Well, you will be very surprised to learn that coprolites as described above were found in one site that show this diet was commonplace for over 9,000 years[13]!


At this point I hope the plot is not lost, that was a lot to take in.  I have shown you how microbes evolved and shaped our evolution.  How man ate for millions of years in a way to support the very essence of his being and how modern eating is completely at odds with keeping our intestinal microbes healthy and in turn, keeping ourselves healthy.  The brain-gut connection is real and cannot be ignored, to do so is to ignore over two million years of evolutionary learning. 

Whatever your personal beliefs are on how we all got to where we are today doesn’t matter one iota, but to deny the existence of of the trillions of bacteria living inside you, is pure folly to the nth degree.  Organic farmers know the importance of soil microbes and continually  fine-tune their microbe-rich compost heaps, adding this or that to turn a pile of steaming dung and kitchen scraps into food for their nutritious crops.  We, in-turn, eat the plants grown in microbe enriched soil and ingest microscopic hoards of clingers-on.  This same story has played out for countless eons and these microbes shaped not only our food, but us.  Our fairly recent departure from intimate contact with the soil and its inhabitants has left its mark on our DNA.   

[1] "Invention of cooking drove evolution of the human species, new ..." 2010. 24 Jan. 2014 <>
[2] Zhang, Y. "The in vitro effects of retrograded starch (resistant starch type 3) from ..." 2013. <>
[3] "Earth oven - Wikipedia, the free encyclopedia." 2005. 17 Jan. 2014 <>
[4] Champ, M. "Advances in dietary fibre characterisation. 2. Consumption ..." 2003. <>
[5] "Hinds Cave > Life at Hinds - Texas Beyond History." 2005. 17 Jan. 2014 <>
[6] Kuch, M. "Extraction of DNA from paleofeces." 2012. <>
[7] "Medicine Across the Cultures - Scribd." 2011. 17 Jan. 2014 <>
[8] "Paleofeces (coprolites) - PaleoResearch Institute." 2003. 17 Jan. 2014 <>
[9] "Iron Age warriors point to glories of Gaul -" 2013. 17 Jan. 2014 <>
[10] "Assessing Diet and Seasonality in the Lower Pecos ... - Repository." 2012. 17 Jan. 2014 <>
[11] "Paleofeces (coprolites) - Paleo Research Institute." 2003. 24 Jan. 2014 <>
[12] "Coprolites & Gastroliths." 2008. 24 Jan. 2014 <>
[13] "A nutritional analysis of diet as revealed in prehistoric human ..." 2010. 17 Jan. 2014 <>


  1. About cooking - this may be one of just many uses of fire, perhaps a side one. Fire was useful for other reasons, one of them was mentioned by Joel Salatin, and then later on Richard Nikoley's blog in the comments - to artificially keep savannah/grassland instead of the forests. And for defense against dangerous animals as well just for heat.

    Besides the real deal - the introduction of the creative version of Homo Sapiens, sometime like starting 70k years ago, during so-called Cultural Revolution. Much later than fire, cooking, much earlier than agriculture. May be associated with introduction of a lot of seafood/fish to the diet.
    When you look at Homo Erectus, Neanderthals or other archaics what you see is rapid growth pattern of children, as well as having a robust (eg. large prodruding jaw) adult form. Quite a lot like chipms - a young chimp has this a human like look, can smile etc., but it quickly looses it, as it transforms into this large-jaw adult form. It's even worse with male organgutans that grow side plates.

    We, modern humans are more like the eternal teenagers, starting with very slow growth, then having this babyfaces, with tall foreheads, tiny jaws, no browridghes, unlike archaics. It is suspected that this gives us the ability to learn efficiently even when sexually mature, after reproduction, while in the middle age. Older versions of hominids had this fault that the technology was stack with the species. A new species arrived = new technology, but then no progress, or even regional variation, for thousands or hundreds of thousands of years. Simply impossible with modern people so it has to have a strong genetic component. First version of anatomically modern HSS also didn't have much progress, only the ones around the cultural revolution had introduced a persisten innovation as a feature of the behavior. So there's this question what happened then that is quite important, and not fully solved.

    About pollen - some has hormonal properties. Like pine pollen being testosterone-like.

  2. Prickly pear cladodes, persimmon and mesquite seeds, nopales, lechuguilla and sotol caudices - the names are exotic enought to sell such stuff in the health food stores. Whole rats - probably not.

  3. Maybe a little off topic, but have you seen this article in Nature??

    Jo tB

  4. I just finished the book. I thoroughly enjoyed it, but I like books about human evolution. He is certainly good at constructing ordered, organized, and efficient arguments.

    I am too disappointed that he did not discuss more the connection to the gut biome. I think he'd have interesting things to say.

    I especially liked the epilogue. It made me realize that the weight loss I've experienced being on a high fiber diet might also be connected to changes in my cooking. I cook a lot less of my meals. I remember before I started that preparing meals was harder because my main meats and side dishes were all cooked, and I have to work out the timing. I have several grills, and I'd have two or more going so that I could cook sides at the same time as meat. I don't do that any more. The main dish is usually cooked, but the sides are usually not. Even if I make a roast, I cook turnips and parsnips just for a short while, certainly still crispy. Nothing like the mush I used to make.

    My digestive system probably uses a lot more energy than it used to given this and the high fiber.

    And Wrangham suggests that I am even less efficient on digesting the food I do eat, so that it provides fewer calories than it would otherwise.

    At the beginning of the book, it seemed that Wrangham thought the softer, industrialized food was a good thing. It was clear in the epilogue that he does not. A very enjoyable read.

  5. Video is free until 1/02/15 - good information...