Fitting our Genes


By Brian Tomas

The Boulder Trail Running Breakfast Club is a Saturday morning meetup group that combines my three favorite things: trails, running, and food. Others agree; it’s a popular group, size-limited in summer by trail regulations that make for waiting lists. The hours fly as we run. The trails and the conversation are all over the map, but they loop back – the talk to how much we love the trails, the running, and the breakfast. Why the love? Maybe it’s about fitting our genes.

Within each of our cells is the recipe for who we are: our DNA. Our DNA connects us to each other, and to the web of life. You and I and everyone we know, everyone on Earth, are descendants of one person – Mitochondrial Eve – in an unbroken maternal line. Through our DNA, we’re a link in a chain from a single-cell organism to our children and the future of humanity. It’s an everyday miracle. A miracle that suits us, like other animals, for being outside in nature; that shapes us as the best endurance runners on the planet; and uniquely tailors us for cooking. These adaptations are part of our DNA, the hardware half of fitting our genes.

The same hardware, the same DNA, is used in every cell in your body. But your liver is nothing like your bones, and somehow your cells know. Gene expression is how the information in DNA is used to make the RNA and the proteins that are the macromolecular machinery of life. This is the software half of fitting our genes, and our behavior and our environment continuously reprogram our gene expression. We know that exercise, wholesome food, and de-stressing make gene expression healthy, and conversely, couch vegetating, junk food, and stress overload make gene expression sickly. Long term, it’s serious as cancer – and other chronic diseases, the leading cause of disability and death.

Exercise and healthy nutrition strengthen bones and muscles, improve mood and cognitive function, reduce aging effects, and reduce risk for cardiovascular disease, diabetes, and some cancers. Spending time in nature lowers stress and boosts immunity. Why? For now, the mechanisms are poorly understood. Knowing why may someday give individualized prescriptions for diet, workouts, and de-stressing. And maybe knowing why can be monetized, something like a workout in a pill. I’m happy knowing what fits our genes – it’s no accident they’re my favorite things.

If you’re a science fan, you’re probably wondering: what about epigenetics? Broadly, epigenetics is the study of changes in gene expression, but epigenetics has come to mean how these changes are “written” into our genes, and are possibly passed on. There’s cutting debate whether epigenetic changes cause or merely reflect physiological changes, and whether they can be passed on in humans. Skeptical geneticist Kat Arney sums up the discord: “Epigenetics… many people keep using that word, but it does not mean what they think it means.” The meaning of epigenetics is murky, and it’s clear epigenetics is suffering growing pains.

Epigenetics aside, let’s focus on what we do know: gene expression gets an extreme makeover from exercise, diet, and being in nature, and it’s rooted in our evolutionary past. Our genome used to be called our blueprint, but now we know it’s like the menu at better restaurants – a starting point – and every day, what we order up makes it better or worse. We cannot not choose.

The cooking hypothesis and the endurance running hypothesis are recent propositions about our distant past. I hope they float your wonder boat. From 1.8 million years ago until about 50,000 years ago, running and cooking were our ancestor’s everything: food, warmth, the tipping point for socialization and intellect, life and death.

Shinrin yoku is the Japanese practice of forest bathing: simply walking through wooded areas. Shinrin yoku is a medical stress management therapy in Japan with proven health benefits, all for just being outside in nature. Stress reduction is one of the three big lifestyle choices affecting gene expression, rounding out exercise and nutrition. And trail running may double de-stress.

Aesthetics is the study of the appreciation of art and beauty. Evolutionary aesthetics is the hypothesis that human aesthetic preferences evolved because of survival or reproduction success. Unlike the endurance running hypothesis and the cooking hypothesis, there isn’t anthropological evidence to support evolutionary aesthetics. But the universality, high emotions, and deep commitment attached to aesthetic behaviors makes a statement about who we are and how we should live.

Winter run, Boulder Trail Running Breakfast Club. Photo: Patrick Nguyen

Endurance Running Hypothesis

Through Mitochondrial Eve, we’re all genetically related, and by the Endurance Running Hypothesis, we’re all of royal descent – the imperial endurance runners on Earth. It was no accident. Over 2 million years, we evolved a constellation of adaptations, wholly for running, that shaped our bodies from head to toe – 26 adaptations, last count. Running shaped us and made us human. Evolution is a master bio-smith, and our adaptations for running are second only to the sovereign evolutionary miracle, reproduction. Like a Ferrari, performance comes from a multiphysics system.

Stability relies on skeletal specializations like our neck’s nuchal ligament and muscles like big gluteals. Energy storage and efficiency – range and mpg – are key. We store enough high performance glycogen in our muscles and liver for about 20 miles, and we can also burn an almost endless supply of fat efficiently, with hormonal help from large thyroid and adrenal glands. Longer legs and shorter toes give stride efficiency. The achilles tendon acts like a pogo stick spring, rebounding energy from each running stride.

In the African savanna where our ancestors ran, cooling was as important for running as mpg and fuel range. In the long run, kudus and elands overheat before humans do because we’re water cooled, and they’re air cooled. Humans sweat over their entire bodies, and most other running animals cool by panting. And later hominins, including us, have less body hair for faster cooling.

Homo erectus, and later species, were efficient and cool enough to run big game to exhaustion, then finish them off with low tech tools like clubs and stones. Weapons like the atlatl and bow and arrow, and even dogs were still over 1.7 million years away. Running prey to death is called persistence hunting, and together with scavenging and cooking, it was our evolutionary niche.

Our running (and walking) is efficient over our entire range of speeds, unlike other animals. Kudus and elands and other running grazers are much less efficient and heat up much faster when they speed up from a trot to a gallop – which happens right around the speed of good human marathon runners. In this way, our running connects us to the web of life. If kudus had trotted faster, we’d run sub 2 hour marathons today; or not have ever been.

Cooking Hypothesis

Animals use tools and language. Bees dance, birds sing, and African elephants make subsonic long distance calls. Linguists like Noam Chomsky argue there’s an evolutionary spectrum of language bridging humans and animals. Otters stone hammer shellfish open, chimps hunt with sharp sticks, and Darwin watched baboons roll stones downhill at enemies.

But only humans cook. According to the Cooking Hypothesis, cooking shaped us and made us human. The way to man’s genome is through his stomach. And our cooking adaptations are conjoined with our endurance running adaptations.

With his small book Catching Fire, Harvard anthropologist Richard Wrangham wrote a big new chapter of human evolution: the Cooking Hypothesis. Even Darwin missed it. Cooking is an evolutionary game changer. And like our running endurance comes from a multiphysics system, our culinary upper hand comes from a multi-biology system.

Cooking changes food chemistry: more foods are edible and all foods are easier to chew and digest. Cooked food is high performance fuel, with less effort to top the tank. Cooking kills harmful bacteria. And cooked food tastes better. A tasty hot meal and a cozy fire were the origins of human socialization, argues Wrangham. And today, almost two million years later, shared meals are still our social centerpiece. Chimps don’t share food with their tribe. Humans do.

About 1.8 million years ago, hominin teeth and jaws and guts got smaller and brains got bigger – adaptations that fit in with cooking. Endurance running is hard with a big gut, and the same time their guts shrank, our ancestors adapted for running. The game changing connection: the persistence hunt. For most of hominin history, it was run and cook or starve.

Exercise and Gene Expression

Running shaped us and made us human. For most of our evolutionary past, running was as important as brains, as serious as life and death. Today’s chronic disease isn’t as dramatic as prehistoric starvation, but running and exercise are just as important.

Our muscles do much more than move us here and there. Skeletal muscles are big and bossy: they are 30-40% of our body weight, and use up to 25% of our energy at rest, more than our brains at work. Muscle activity, or inactivity, is the boss of our gene expression. Exercise enhances metabolism, fat storage, cardiac function, immune response, cognitive function, and mood; lowers inflammation, blood pressure, and the risk of some cancers; and slows aging. Inactivity does the opposite – lack of exercise is a major cause of chronic disease.

Muscles continuously change composition with levels of exercise, and the use it or lose it of muscles is the wellness or illness of the whole-body. Gene expression is why, but how, we don’t know. There’s a clear association between epigenetic markers, gene expression, and exercise, but the exact mechanisms aren’t clear. In her witty, irreverent chapter “Pimp my Genome,” Kat Arney dissects epigenetics, exposes weak but popular conclusions, and stitches up a case for skepticism. Popular reports and press releases are often exaggerated. Maybe someday you’ll be able to spit in a tube, send it off to a lab, and get back a workout program that fits your genes – but not today.

General exercise guidelines recommend 2.5 hours of moderate exercise like brisk walking, or 1.25 hours of vigorous exercise like running per week, plus 2 bouts of vigorous strength training. While any exercise is better than none, meta studies show more is better – there’s an inverse risk of heart failure with up to 4 times the general guidelines. Benefits from more exercise plateau, but there doesn’t seem to be an increased risk of heart failure with more exercise, up to 10 times the general guidelines. There are inherited individual risks with high levels exercise, but there doesn’t seem to be a general harmful high level of exercise.

Diet and Gene Expression

Cooking shaped us and made us human. On an evolutionary time scale, what our ancestors ate changed Homo sapiens’ genes, and what we eat today changes the expression of our genes. The effect of diet on gene expression is complicated by geographic genetic variations – for example, lactose intolerance, and regional adaptations to vegetarian and seafood diets – complicating general guidelines. On the other hand, more specific studies can tailor dietary recommendations to genetic variations.

General diet guidelines include bushels of fruit and vegetables – dark green, red and orange – whole grains, nuts, low-fat dairy, eggs, seafood, legumes; and limiting sugars and saturated fats. These are supported by studies of gene expression profiles, which correlate with healthy immune and inflammatory response and reduced risk of some cancers and cardiovascular disease.

The Mediterranean diet overlaps the guidelines, and the PREDIMED study shows improvements in metabolic syndrome, blood pressure, lipid profiles, lipoprotein particles, inflammation, oxidative stress, and carotid atherosclerosis – improvements which correlate with changes in gene expression. A meta-study showed improvements in cognitive function. And in another study, a group genetically predisposed to cardiovascular disease reversed high blood pressure, cholesterol, and triglycerides levels to normal on the Mediterranean diet. Some day, nutrition plans may be personalized by genetic testing, but today results are limited and testing is expensive.

The Mediterranean diet includes lots of olive oil, regular dishes of fatty fishes, and a glass of red wine, plus lots of vegetables, fruits, nuts, and little red meat. Fatty fishes like sardines and salmon have lots of omega-3 fatty acids.

More specific studies show that balancing omega-6 and omega-3 fatty acids reduces expression of key signaling genes that promote inflammation and autoimmune response. Modern diets have up to a 10:1 ratio of omega-6 to omega-3 fatty acids; anthropological evidence suggests our ancestors had a ratio of 2:1. Some foods high in omega-3 fatty acids are chia and flax seeds, fatty fishes like salmon and sardines, and shellfish like scallops.

It all starts with grocery shopping. Plan ahead. Stick to the perimeter, avoid the junk food aisles and ends. Fill up on produce, try a different fruit or vegetable. Top off on dairy and fish. Buy foods your great grandmother would recognize.

Shinrin yoku

Lifestyle medicine is an approach to medicine that focuses on lifestyle choices for preventing and treating disease. The top three do’s in lifestyle medicine are diet, exercise, and stress management. There are personalized approaches to lifestyle medicine, and lots of techniques for stress management. My favorite is just being in nature.

Shinrin yoku, forest bathing, is a walking trip to a forest – prescribed in Japan for stress management. Studies show it reduces levels of cortisol, the stress hormone, and improves immune function. Similar walking trips in the city didn’t show these benefits. And a study in the UK found more frequent nature walks are more beneficial.

By de-stressing, Shinrin yoku fits our genes. Chronic stress increases risk of disease and early death, and the risks are associated with changes in gene expression. And in mice, wheel running reduces the impact of stress on genes; perhaps trail running has a double de-stress synergy.

Evolutionary Aesthetics

The love of nature, of being in nature is universally deeply rooted. More broadly, the hypothesis that our aesthetic preferences are an evolutionary adaptation is called evolutionary aesthetics. Unlike the endurance running hypothesis and the cooking hypothesis, it’s not supported by anthropological evidence. Evolutionary aesthetics is theoretical and philosophical, and in my opinion, fascinating.

Nature is a universal and ancient theme in poetry and visual arts. Landscape painting has rich traditions, in Europe back to the Renaissance, and in China back to the Tang dynasty. Mountains, waters, and groves are sacred in many religious traditions.

Scandinavian countries – the happiest on Earth – celebrate friluftsliv, which literally means “free air life,” but is difficult to translate. Friluftsliv is a philosophy of exploring and appreciating nature, and and the name of a course at Norwegian high schools. Scandinavian primary schools have adopted Iceland’s Biophilia Program. The biophilia hypothesis claims the bond between humans and nature is intrinsic.The United States doesn’t have a nature curriculum, but its national park system does have over 270 million visitors a year. Our attachment to nature is universal, timeless, and deep.

Big questions like who am I and how to live will never have complete answers from science, philosophy, or religion. But evolution and genetics can give clues, clues to happier and healthier lives. And it just feels good to fit our genes.


1 Comment

  1. Amanda Bloom on

    Interesting article, however there needs to be a correction: chimpanzees do share food. They have a complex societal structure where they not only will share food, but they will adopt orphaned baby chimps among other things. It is also worth noting, that the adopting of orphans has been observed in males as well as females.