April 2009 Issue

Evolutionary Eating — What We Can Learn From Our Primitive Past
By Juliann Schaeffer
Today’s Dietitian
Vol. 11 No. 4 P. 36

Believing our genes are nutritionally tied to the Paleolithic age, some scientists are hunting for clues and gathering answers that may shed light on modern disease and dietary imbalances.

We live in a digital age—a world in constant motion, constant change. So one may question, understandably so, what today’s technology-toting, fast-food–frequenting individuals could learn by looking back on the lives of hunter-gatherers from the Paleolithic Era, a period that lasted about 2.5 million years and ended around 10,000 years ago with the development of agriculture. According to some scientists, modern humans could gain some valuable dietary insight.

Arguments exist regarding the specifics of hunter-gatherer cuisine, partly because diets varied widely depending on the region and partly because hunter-gatherers existed over a period of thousands of years, during which different foods were likely available and utilized. But scientists generally agree that our Paleolithic hunter-gatherer ancestors likely ate a combination of foods that could be hunted or fished, including lean meats and seafood, and some that could be gathered, such as fruits, plants, nuts, eggs, insects, mushrooms, herbs, and spices.

In comparison, estimates indicate that up to 70% of Western dietary calories could come from foods that weren’t available to those living in the Paleolithic Era (think refined cereals, sugars, and vegetable oils). And although our world may be evolving at a digital speed, according to some scientists, many of our genes are still stuck at the hunter-gatherer dinner table.

A Modern Diet for Ancient Genes?
Some in the scientific world say humans are not genetically adapted to eat a sizeable percentage of the average modern diet—foods that first came into existence in the Neolithic Revolution with the introduction of agriculture and animal husbandry about 10,000 years ago, and even more so with the industrialization of the food system in the Industrial Age.

As the advent of agriculture slowly shifted once–hunter-gatherers from nomadic tribes into larger societies to tend crops, everyday diets also shifted, allowing for the consumption of large amounts of grain, milk, and domesticated meat. Then came the Industrial Age (a mere 200 years ago), when whole grains and sugar were refined. This reliance on more processed foods than fresh foods effectively led us to where we stand today—likely within 5 miles of multiple fast-food joints.

Some scientists argue that our genes simply haven’t caught up with this dietary divergence and that it could be causing—or at least contributing to—the epidemic levels of chronic disease, such as cardiovascular disease, cancer, diabetes, and obesity, that we see today.

“Although evolution is an ongoing process, for all living people, their genome is a result of past events in the generations of humans who came before them,” says Loren Cordain, PhD, a professor and the author of The Paleo Diet. “Only 330 human generations have come and gone since the development of agriculture. Before this time, all humans on the planet made their living as hunter-gatherers. Although a number of genetic changes have occurred since the agricultural revolution, the majority of the human genome has resulted from the environment of our hunter-gatherer ancestors and earlier.”

Thus, Cordain says, modern humans, like all species, are genetically adapted to the environment that their ancestors survived in and that conditioned their genetic makeup. And according to George Armelagos, PhD, a professor and the department chair of anthropology at Emory University, the genotype of hunter-gatherer populations was adapted for times of feast or famine, which can be seen in the way fat accrued on the body. Today, that genotype could be causing problems due to the excessive amounts of carbohydrates some people eat.

“That genotype, once you have abundant carbohydrates, becomes a health problem with diabetes,” says Armelagos. “We have a genotype that was developed for the grasslands and the forest, and now we live in the canyons of cities. With the 10,000 years since the development of agriculture, there just hasn’t been enough time to alter the genetic structure of the human population. … From a dietary perspective, it’s not likely that there’s been very many major [genetic] changes. I think with the development of agriculture, the basic way in which we consume proteins and carbohydrates hasn’t changed.”

One may expect our preagriculture ancestors to have a less balanced diet than that of today, when grocery stores house endless options of countless foods, but Armelagos says that isn’t so. “During the Paleolithic period, there was a much broader pattern of food consumption. Even though they may have had aspects of famine, they had a wider range of foods and so they had a more balanced diet,” albeit accidentally, he explains. “With the impact of agriculture, you tend to have a selection of superfoods. For example, in Native Americans, it may be maize, which is lysine deficient, and that creates [nutritional] problems.”

This reliance on superfoods caused not only an increase in infectious diseases in agricultural societies but also a decline in nutritional health, he says, which was only exacerbated by an Industrial Age that brought an abundance of high-density foods to humans.

According to Armelagos, 2 million years ago, our hominid ancestors experienced a decrease in the length of the large intestine and an increase in the length of the small intestine, which forced the early hominids to rely on high-density foods. “That’s no problem during the Paleolithic period and probably not even in the Neolithic period,” he says, because there was never an abundance of high-density foods available. But with the industrialization of the food system, which happened only a few hundred years ago, “came the abundance of high-density foods, which can create problems for humans in terms of overconsumption,” he notes.

In Cordain’s view, the evolution of our diet may provide answers to the emergence of modern disease, as many chronic diseases manifested only after the advent of agriculture. “Humanity is genetically well adapted to the lifestyle of a hunter-gatherer, including the food types that they consumed and their exercise patterns. As the famous scientist Theodosius Dobzhansky once said, ‘Nothing in biology makes sense except in the light of evolution.’ As nutrition is a subdiscipline of biology, it could be said that nothing in nutrition makes sense except in the light of evolution. No matter how absurd it may sound at first glance, the direction and clues that evolutionary evidence provides for optimal human nutrition is invariably correct,” he says.

Cordain uses dairy as an example. “No hunter-gatherer ever consumed milk after weaning and rarely, if ever, consumed cereal grains. These two foods comprise approximately 35% of the energy in the typical U.S. diet. By keeping an open mind to the biological laws that govern all living processes, including nutrition, nutritionists who utilize this powerful tool will uncover new information linking diet to disease,” he says. “Currently, hundreds of diseases with no known cause inflict humanity, particularly autoimmune diseases such as type 1 diabetes, multiple sclerosis, rheumatoid arthritis, psoriasis, and others. An increasing body of evidence is now implicating diet as the environmental trigger that elicits these diseases in genetically susceptible individuals, and the dietary factors in all of these diseases are foods and food groups introduced after the advent of agriculture.”

Paleolithic Dietary Details
Before agriculture’s onset, scientists generally believe that hunter-gatherers derived their foods mostly from minimally processed plants and animals. As Armelagos and Harper wrote in “Genomics at the Origins of Agriculture, Part One” in Evolutionary Anthropology, “For thousands of millennia, hominids existed as foragers who, it has been suggested, struggled to eke out an existence by gathering and hunting in marginal environments.”

But with agriculture and animal husbandry, as well as food industrialization, the food supply broadened substantially, allowing for the introduction of many new foods and altering the nutritional characteristics of the average diet. According to a 2005 article in The American Journal of Clinical Nutrition, Cordain et al argue, “The novel foods (dairy products, cereals, refined cereals, refined sugars, refined vegetable oils, fatty meats, salt, and combinations of these foods) introduced as staples during the Neolithic and Industrial Eras fundamentally altered several key nutritional characteristics of ancestral hominin diets and ultimately had far-reaching effects on health and well-being.”

Compared with the typical Western diet of today, Cordain says hunter-gatherer diets from the late Paleolithic Era likely exhibited the following nutritional characteristics:

• a lower glycemic load;

• a net base yielding to the kidney;

• higher potassium and lower sodium levels;

• higher fiber levels;

• different fatty acid intake (higher omega-3s, lower omega-6s, more highly unsaturated fatty acids of both omega-3s and omega-6s, lower trans fatty acids, higher monounsaturated fatty acids and polyunsaturated fatty acids);

• more protein and less carbohydrate; and

• more vitamins, minerals, and phytochemicals.

Because Cordain believes these altered nutritional characteristics are interfering with contemporary humans’ mostly ancient genes, diseases such as cardiovascular disease and diabetes, he created the Paleo Diet, which he says is a way of eating in the modern age to best mimic the nutrition of our evolutionary and genetic heritage.

Although modern lifestyles don’t allow for the utilization of primarily wild plants and animals as a sole nutrition source, Cordain says modern humans could still use the general characteristics of the hunter-gatherer diet to maximize health benefits. “Clearly, we cannot eat wild plant and animal foods as our sole nutritional source, but by mimicking the nutritional characteristics of these foods with common foods available at the supermarket, we can markedly improve our health,” he says.

Cordain’s recommendations mirror what many nutrition professionals have been preaching for years: “The basics of the concept are quite simple: Eat fresh fruits, vegetables, lean meats, and seafood. Avoid processed and packaged foods.”

An Argument Against Evolutionary Simplicity
Although certain professionals, such as Walter L. Voegtlin, MD, who first popularized the idea of modeling the modern diet after our Paleolithic ancestors in The Stone Age Diet, and S. Boyd Eaton, MD, Marjorie Shostak, and Melvin Konner, MD, PhD, in The Paleolithic Prescription, pioneered the concept more than a decade ago, not everyone agrees that benefits exist in examining the dietary habits of hunter-gatherers.

Some counterarguments include the suggestion that modern disease didn’t affect hunter-gatherer populations simply because their short life expectancy didn’t allow for it. Other critics ask why modern human populations live so much longer if the diet of our ancestors was so much healthier, while some dispute the idea that roughly 10,000 years was insufficient time for our genome to adapt to an evolving environment.

Still others, like Marlene Zuk, PhD, a biology professor at the University of California, Riverside, don’t discount the idea overall but take issue with its oversimplification, with the notion that “eating like a caveman” will solve all of our modern medical problems. Zuk, who recently wrote an article in The New York Times, “The Evolutionary Search for Our Perfect Past,” says the danger in seeking modern dietary answers in our Paleolithic ancestors is that evolution just isn’t that simple or straightforward.

Noting that the Paleolithic Diet, also referred to as the Caveman Diet, appeals to our sense that life used to be more in sync with our environment, Zuk explains that not all aspects of the human body work perfectly because we technically evolved from fish (and, before that, single-celled organisms), not from scratch. There are a lot of compromises in human evolution, she says, noting hiccups, hernias, and hemorrhoids as examples. “But the reason for that isn’t because evolution messed up; it’s because evolution had to start from a constrained point. And I think that’s an interesting thing to think about in respect to diet, too—that our digestive systems and our teeth had to come from somewhere. They weren’t just invented de novo for people,” she says.

Zuk says it’s often easy to misunderstand the concept of evolution because it’s a complicated process for which not even scientists have found all of the answers. “Different genes change at different rates,” she says. “We share a lot of genes with carnations and sea anemones and lots of other animals; there’s many genes that we have in common with Drosophila [fruit flies]. But nobody’s suggesting we should eat what flies eat, even though we have genes in common with flies.

“You can suggest that there are a lot of similarities in all animals, and so we’re likely to have more genes in common with our more recent ancestors than with our more distant ancestors. But that doesn’t mean that for any given gene, they’ve all changed or they all haven’t changed,” she continues.

Zuk gives humans’ ability to digest milk as an example of a gene that has changed remarkably fast in evolutionary terms. “And yet people will persist in saying that our hunter-gatherer ancestors didn’t drink milk past weaning, but our agricultural ancestors did. And the reason they did is that their genes had changed; there has been evolution since we were hunter-gatherers,” she says, noting that there certainly hasn’t been evolution in every single one of our genes.

Although she laments that many consumers may look to the Paleolithic Diet as a cure-all or an easy fix for bad eating habits, she does see benefit in examining the general rules about how hunter-gatherers ate and what relevance that has to what we’re doing today.

Zuk cites a study of aboriginal Australians that looked for a possible link between an indigenous diet and modern diseases such as diabetes, heart disease, and obesity. “People followed the aboriginal diet—eating a very high fiber content, walking throughout much of the day, digging up wild tubers—and there was a precipitous drop in blood pressure and blood sugar levels,” she says. “So you can demonstrate that eating closer to the way a lot of indigenous ancestors of modern people ate is going to have good effects on the descendants of those people. But that doesn’t mean that everybody needs to be eating yams, for instance. It’s possible that if they ate the ancestral diet of people from southeast Asia or the ancestral diet of the people from South America that they would be doing better as well.

“The only reason we think that people in our ancestral hunter-gatherer societies had these wonderful diets to which they were perfectly adapted to is that they’re not around to talk to us about how it wasn’t,” she continues. “You can see that evolution has affected a lot of aspects of our physiology and the way we do everything. You just don’t want to have an oversimplified idea that you’re applying.”

The Bigger Picture
Armelagos believes that the takeaway message in examining Paleolithic nutrition may not lie in simply reverting clients back to an ancient way of eating but in helping us determine how we got to this place in history—and how best to move forth. “When we look at the evolutionary history, I don’t think what it’s calling us to do is to eat like the caveman. What it’s telling us is how these problems originated. Part of what I’m seeing in the research I’ve done is to let us understand how we got into our current dilemma. Then we might have other ways of dealing with those particular issues,” he says.

Citing a 1992 study published in the Journal of the American Dietetic Association in which Murphy et al found that only 22% of participants were following two thirds of the recommended daily allowances and that only 14% were consuming less than 30% of dietary fat, with only 2% following both of these, he asks the question, “If Homo sapiens are the self-proclaimed wise ones, then why don’t we eat right?”

Whereas Murphy believed the answer to be in better educating the public about nutrition, Armelagos says it could be in better understanding our evolutionary history. “But it’s a difficult task when you have all these systems that can deliver so much food to so many people at such a low cost,” he says.

“If you look at it from an evolutionary perspective, you have first the evolutionary change in which you have a demand for high-density foods, which created the major selective force for a couple million years in humans; and then you have the impact of agriculture, which increased the nutritional diseases and infectious diseases. Then about 200 years ago, you have the development of the industrialization of the food system, which further exacerbates the nutritional dilemma that humans face,” he explains.

While agreeing that we could learn much from the generalities of what our hunter-gatherer ancestors ate, Armelagos concludes with where he believes the biggest gain from our hunter-gatherer friends could hide: exercise. “For the time it took the !Kung [hunter-gatherer] woman to go out and collect food, it takes me about 20 minutes to go to the grocery store to get that food and 20 minutes to cook it, [equating to] 40 minutes. It took her two or three hours of going out and collecting. Now the difference is that I have to work to earn the money to pay for that food, but I’m earning that sitting down thinking and writing. If there was anything that The Paleolithic Prescription would tell us, it’s that we need more exercise.”

— Juliann Schaeffer is an editorial assistant at Today’s Dietitian.