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Unintended Consequences: What happed to the Human Hybrid?

By Jeff D. Leach

If you did not read the most recent column – So go the Pima, so go the rest of us – please do so before reading the current column.

As you read this, there are millions of tiny microbes swimming around in the fluid surrounding your eyeballs. But you can’t see them. There are millions more under your finger nails, on your hands, arms, legs and just about every imaginable section of your fleshy real estate. There are millions more lining your moist nasal passage, many more maneuvering about your liver, heart, lungs, pancreas and trillions more living throughout your continuous gastrointestinal tract – from mouth to anus. And as you ponder this unimaginable invasion of invisible aliens, there are millions more setting up new beach heads on that all-important organ between your ears every minute of every day from the moment you entered this world. But that’s the good news.

The bad news is we are literally starving, depressing and killing off an alarming number of these little evolutionary hitchhiking friends with our so-called modern, westernized diet. Our modern food supply, with its 300,000 or so processed products for sale in the U.S alone, is one stunning example of the cultural, technological and political prowess of a species gone wild. So freakish is our modern food supply, I doubt our ancestors would recognize much of it as food at all. Our internal ‘friendly’ bacteria are equally puzzled.

As we fill our shopping carts and pantries with the latest neatly boxed and wrapped goodies of industry, we continue down a path that began some ten thousand years ago with the emergence of agriculture – an event that would eventually, along with steel roller mills in the 1880s and farm subsidies in the 1970s, lead to the greatest “unintended consequence” in human history: The shift in how and where the human body captures much-needed energy (calories) to power our demanding bodies and lifestyle. Let me explain.

This admittedly dramatic pronouncement – “the greatest unintended consequence in human history” – underlies something I have come to call the Human Hybrid. The Human Hybrid is an evolutionary-based way of thinking about nutrition and the tragic epidemic of obesity and its growing list of acute and chronic byproducts (disease). But nowhere is the Human Hybrid more potentially applicable than when trying to wrap your head around the metabolic syndrome of insulin-resistance (sometimes referred to as Syndrome X). If you are overweight, diabetic, have hypertension, low HDL-cholesterol levels, high triglycerides, or have ever suffered a mild heart attack or stroke, then you probably have the insulin-resistance syndrome. More on this in a moment.

The easiest way to begin to explain the Human Hybrid is to think about hybrid cars – the latest must-have techno gadget for the social and environmentally conscious – and financially stable – among us. The concept behind hybrid cars is simple: a mixture of power technologies such as internal combustion engines and electric batteries (and in some cases electric motors) are applied to create a more efficient system. In other words, two power sources. On the front end you have a gas-powered engine that works to push the car forward part of the time, with the second power source (batteries) in the backend making up the difference a certain percentage of the time. 

The clever engineers who devised the hybrid car designed it to run on both sources – not one or the other full-time. They share the work. Running the entire system on one or the other exclusively, would result in the system malfunctioning and falling part. The two energy system was designed to share in delivering the power needs. Like the hybrid car, humans have two major power sources – one in front end (small intestine) and the other, quite literally, on the back end (the colon).        

Our Human Hybrid is a hold over from our days of hanging out with other primates and enjoying those low-energy dense meals of roots, leaves, fruits, bark, seeds, insects, and flowers. The good ol’ days. Between 5 to 7 million years ago, the diet of our ancestors – who looked nothing like us at the time, and pretty much like our friends at the zoo – was dominated by lots and lots and lots of fiber. To extract enough calories from this bulky diet, our early tree swinging cousins relied on millions of years of co-evolution with an unlikely cast of microscopic hitchhikers and some ingenious arrangements.

As food passed through our early ancestors stomach and small intestine, enzymes broke down the material allowing for fats, proteins, carbohydrates, minerals, vitamins and so on to be absorbed. Anything not broken down (fiber) was moved on. By definition, fiber is pretty much anything that escapes digestion and absorption in the small intestine and ends up in the colon – end of the line. Far from being wasted plant material at this last station in the gastrointestinal system, the trillions of bacteria that lived in our early ancestors colons went about the task of breaking down that fiber through a process called fermentation and turning it into energy. The bacteria relied on this “fiber” to live (i.e., fiber is food for bacteria!). In the process of fermentation, a byproduct known as short chain fatty acids, with names such as acetate, butyrate and propionate, were generated and then absorbed and used by cell and organs of the body as energy. Voilà! Energy (calories) from bark.

Rough estimates suggest that our early ancestors generated as much 25 to 35% of their energy needs by this hybrid energy technology. Primates living today still rely on the bacteria and the energy they generate to continue to make a living on the lush greens of the world’s tropical – but shrinking – forests.

As our earliest ancestors took those first tentative steps onto the open savannahs of Africa – and began their march to global mammalian dominance all those millions of years ago – they took with them this fully-developed hybrid energy technology and its bacterial power plant for the evolutionary ride. Today, this same cast of characters is still with us, known by names like bifidobacterium and lactobacillus (If you eat yogurt you will recognize these names as they are added today under the heading of probiotics).

But during that long march that ultimately ended in us, our diet improved as we explored new lands and developed technologies to extract more energy and nutrients from our environment. Over each new horizon, novel plants and animals presented themselves – and we ate them. We learned to fish, hunt, and to master fire – cooking food, making it more digestible and unlocked nutrients in quantities and diversities never before seen in primate-human history. And then within the last 10,000 years or so, pay dirt – agriculture, pottery, towns, cities, the wheelbarrow, Roman bathhouses! We never looked back.

As the quality and diversity of diet improved with every novel plant and animal we added to the menu, we digested and absorbed more and more energy and nutrients in our small intestine – the front power plant in our Human Hybrid. Through time, this resulted in an increase in the size of our small intestine to handle the windfall. Over the course of a few million years, our small intestine essentially doubled in volume – thus increasing the amount of energy absorbed in the front end. On the flipside, our colon (back end energy source), with its reduced role as a function of us eating less and less fibrous material, reduced in size by more than half (Click here for a colorful graph comparing the stomach, small intestine, and colon of modern humans to that of modern primates).

Nevertheless, our modern colon still accounts for approximately 20% of the total volume of our omnivorous gastrointestinal system. Compared to the colon of meat-eating carnivores, such as the wolf, it’s down right huge.

The simple fact that the colon still represents a significant portion (by volume) of our modern gastrointestinal system, speaks to its continued and important role in our Human Hybrid as an energy source. If we did not need it to generate energy, evolution would reduce its size, say to that of a strict carnivore. Put another way: though our genome has evolved to less dependence on fibrous plant material through time, the fermentation factory – and its bacterial workers – is open for business today and will likely be so into the foreseeable future (a few hundred thousand years without a doubt).

So 1,300 words or so later, you are probably wondering what this has to do with obesity and diabetes among the Pima Indians of Arizona or for modern humans in general. Quite alot, actually.

Even though our modern colons still occupy an important place in our gastrointestinal system and our overall nutrition, and the lights are on in the fermentation factory and trillions of bacteria (some 1,000 plus species) are standing at their stations waiting to do what they do best, our so-called modern and technically slick food supply and industrial and political landscape over which it flows, have something else in mind – and fiber (food for bacteria and fuel for the backend power station of the Human Hybrid) ain’t it.

By all estimates, modern humans should still be generating between 12 to 18% of our daily basal energy needs from the colon part of the Human Hybrid system through fermentation of dietary fiber. For the average American or European who consumes a scant 12 to 15 grams of dietary fiber a day, the energy being provided by the backend is somewhere less than 5% - even less for some. So how does this short fall translate into something tangible for or about modern human health? Quite simply, it means the front end component (small intestine) of the Human Hybrid is providing the majority of the energy demands and in the process, being over worked – exactly what we do not want in a hybrid system of any kind.

The overworking of the front end is coming in the form of rapidly digested and absorbed foods that dominate our modern diet. This includes all those foods our ancestors would not recognize that are laced with added sugars, fats and highly processed nutrient- and fiber-poor grains (think sodas, ice cream, donuts, most breads, chips, most pizzas and burgers, a lot of the dairy products, and so on). As we eat more and more of these front end fuels, we are eating less of the backend fuel (fiber). The average American and European is getting nearly 60% to 70% of their total daily calorie needs from these front end fuels. This would be like pouring kool-aid in your gas tank and expecting everything to run the same as usual. Something has to give, and it is. Enter the hormone insulin and insulin-resistant syndrome – a root problem in a staggering number of modern ailments.

Since this important story needed to be told in such detail – hence it’s length so far – I will restrict the remainder of the discussion to the development of diabetes and the role of the Human Hybrid (hang in there almost done!).

The eating habits of our ancestors more or less adhered to the Human Hybrid diet that developed from the nutritional landscape on which our genome was selected. Our food supply consistently included up to and more than 100 grams of fiber a day – sometimes more, sometimes less. This meant our “minimally processed foods” contained copious amounts of slowly digested carbohydrates – an essential fuel for the red blood cells and brain, and the main source of energy for muscles under conditions of exercise (something that characterized everyday life for our ancestors).

For over 99% of human history (>2 million years), our ancestors main source of carbohydrates (primary energy source) were wild plants foraged from the ancient landscape. The sugars and starches (carbohydrates) in these plants were broken down by the enzymes in the mouth, stomach and small intestine (front end of the Human Hybrid) and absorbed into the blood stream along with other nutrients and utilized by the cells as energy.

Plant parts that are, due to their either chemical or physical structure (fiber), not broken down in this front end of our Human Hybrid are moved along to the next energy station, the colon.

The most common and important of these energy sources is glucose – a building block of starch. Once glucose is absorbed into the blood stream the pancreas jumps into action and excretes the hormone insulin that binds with the glucose and allows it to be utilized as energy. A cellular key of sorts. Without insulin, the glucose cannot be utilized. And this is where the problem begins.

Our ancestral diet of was ideal because it provided slowly-released energy in the form of slowly absorbed foods (today we know this as a low glycemic diet). This also helped to delay hunger pangs well after a meal and importantly, it was easy on the insulin secreting cells of the pancreas and did not overwhelm the system with too much insulin or glucose. This system of gradual absorption of glucose and excretion of life-giving insulin was what our ancestors evolved on for millions of years and what our genome was selected upon. Like the very specific engineering of a hybrid car – which requires finely tuned inputs and interactions between components with everything operating just as engineered or else things don’t function properly – our Human Hybrid was built in a similar Wikipedia-like way with slow and gradual shifts in diet over huge spans of time – evolutionary time.

Our recent adoption (mainly in the last 200 years, but more so in the last 30) and obsession with industry and government promoted “quick” energy in the form of easily digested and absorbed sugars and highly-processed grains, is throwing everything off. (To get my take – rant – on the U.S. Food Pyramid click here).

When we start overwhelming the finely tuned Human Hybrid with too much glucose from highly-processed foods we are asking the pancreas to excrete more and more insulin at a faster rate. At the same time, we are also bombarding the cells in our muscles and organs with this never-ending flood of glucose and insulin at a rate and quantity never before seen in human history – something they were not engineered to handle. Asking the insulin-generating pancreas to put in overtime often (and usually does) results in it finally malfunctioning (lower insulin levels) or giving out entirely. Without insulin to bind with, the glucose stays in the bloodstream. We know this condition of too much blood glucose as hyperglycemia, or by its more common name, diabetes (type 1 diabetes, of course, is when the pancreas can no longer produce insulin).

Of specific interest to our Human Hybrid is insulin-resistance, which occurs when the normal amount of insulin secreted by the pancreas is not able to unlock the door to cells.  To maintain normal blood glucose, the pancreas secretes additional insulin.  In some cases, when the body cells “resist” or do not respond to even higher levels of insulin, glucose builds up in the blood resulting in the dreaded type 2 diabetes.

So why do the cells resist this much-needed energy? Like a sponge full of water, the cells are saying “enough!” – even when they are not full. Have they become exhausted from trying to keep up with all that insulin and glucose? The science says, maybe – most likely, yes. We know that our unfamiliar, rapidly absorbed, diet is triggering some deeply buried genetic instruction to do so. In other words, the Human Hybrid is out of whack.

And for the Pima Indians of southern Arizona, with the highest recorded rate of diabetes of any group on the plant, it seems to be “just a little” bigger problem. What in their evolutionary past – or more correctly, their nutritional past – predisposes them to this terrible disease over, say, a European? I think it might be in the “fine-tuning” or “final touches” on their Human Hybrid fuel system.

Up until about 10,000 years ago, all humans on earth were hunter-gatherers – making a living on wild plants and animals gathered about the landscape. No pottery, no agriculture, no animal husbandry. Pottery and agriculture first took hold in southeastern Asia, then Mediterranean and then spread throughout what is today modern Europe. So over a period from 5,000 to 10,000 years ago just about everyone in Europe was making a living on a limited number of agriculture products and cooking pots (minus a few pockets here and there). For our Human Hybrid, this meant easier to digest grains – shifting from whole grains to minimally processed ones. And as the grains become smaller and smaller (think coarse flour) with each new grinding technology, the sugars and starches become more digestible and thus required “slightly” more insulin for these increasing levels of glucose in the bloodstream. So far so good, as the process was slow and gradual taking place over thousands of years.

But for the Pima of southern Arizona, dependence on finer and finer flours from cultivated grains occurred much later. Throughout much of the American Southwest people started dabbling with agriculture about 3,000 to 4,000 years ago – but it was not until about 1,250 years ago that it started to dominate the menu. This is thousands of years after it already took hold in the ancient European diet. And for the arid American Southwest, the recent agricultural grain diet was heavily subsidized by a broad spectrum menu that still included an extraordinary variety of wild plants – hundreds of species.

So while Europeans were starting to introduce more rapidly absorbed agricultural grains and seeking acceptance from the genome through making slight dietary adjustments (slow ones) to the Human Hybrid engineering (i.e., shifting more of the energy demands to front end – less fiber that is), our Pima friends were still clicking along on the same diet and Human Hybrid blueprint. They would not start to challenge their genome for thousands of more years.

On top of this, the Pima were late comers to the pottery barn – only developing these handy cooking and storage vessels in any appreciable quantities about 1,800 years ago – thousands of years after there European counterparts. Pottery was a significant engineering change to the Human Hybrid as cooking as heat and water make plant foods more digestible. During cooking, water and heat expand the starch granules, making it easier for the enzymes to break them down, and thus to absorb.

So when you fast forward to today and level the playing field with our modern diet – everyone has equal access to the same technology and foods – the Pima may suffer just a little more because engineering changes to the Human Hybrid in the form of novel foods (agricultural grains) and technologies (cooking pots), genetic requests if you will, were introduced later in their evolutionary history. Thus, their genome has had less time to “try” (and I stress try) to adapt. On a metabolic level, this means when you a challenge a Pima Indian Human Hybrid system with more and more rapidly absorbed foods, their tissues exert a hyper reaction and become insulin-resistant just a tad quicker. This basic premise is similar to the issue of lactose intolerance – with some people who have been exposed to the lactose in the milk of domesticated animals for longer periods of time – suffering less from its affects.

And on one final note about the Pima Indians, their ancestors inhabited the arid lands of the American southwest for thousands of years, where the available edible biomass – both plants and animals – is dominated by fiber-rich plants. In other words, arid environments are dominated by plants not animals and the plants are, as a function of their survival mechanisms in such settings, heavy on the fiber side of things – both soluble and insoluble fibers. In fact, when the ancestors of the Pima got around to growing corn, squash and beans (big time) about 1,250 years ago, they also planted fields and fields of the desert succulent agave (agave is the same genus that is used today to make that delicious tequila!).  

So if you squint just a little bit as you look back in time at the Pima ancestors, you see not the famous maize farmers of the American Southwest, but rather you see fiber farmers maintaining their Human Hybrid just as their ancestors had done before them and there descendants will need to do today if they want to break the cycle of disease and misery that a modern/processed diet has brought to these people.

How’s your Human Hybrid?

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