The Paleo Diet, Cordain's 2002 book outlining his experience, urged readers to abandon grains, dairy, and excessive sugar and salt in favor of meat, fish, poultry, fruits, vegetables, and nuts—essentially what humans ate 10,000 years ago, until agriculture came along. “I didn’t design this diet, nature did,” Cordain wrote in the introduction. “This diet has been built into our genes.”

At first, response to Cordain’s book was tepid. It wasn’t until a few years later, around the time that a student of his named Robb Wolf began preaching the paleo gospel, that it became a hit. Wolf ran a health club in Chico, California, and he traveled the country talking up the paleo diet at CrossFit gyms, where athletes were getting beaten into shape through high-intensity circuit training. As CrossFit grew, so did the paleo paradigm, and by the time Wolf published his own book, The Paleo Solution, in 2010, caveman-inspired cuisine had become the de facto CrossFit meal plan. Wolf’s The Paleo Solution was an overnight bestseller.

Since then the paleo lifestyle has become an industry unto itself. Research hasn’t caught up with some of its acolytes’ most ambitious assertions, but what the movement lacks in double-blind studies it makes up for with rabid testimonials. After ditching the Standard American Diet—or SAD, in paleo jargon—converts claim to lose weight, shed gastrointestinal problems like irritable bowel syndrome, and even have their acne clear up.

The success of the diet has inspired a fast-growing library of ancestral-health literature. The paleo ethos now spans every­thing from exercise and entertainment to workplace ergonomics and friendship cultivation. This year a library of new books—including Mark Sisson’s The Primal Connection, Jason Seib’s The Paleo Coach, and Kelly Starrett’s Becoming a Supple Leopard—­continue to expand the paleo gospel.

In The Primal Connection, Mark Sisson, a runner and triathlete who started the popular fitness blog MarksDailyApple.com, strives to “infuse our modern lives with the best and most reasonably reclaimed elements of our evolutionary past, including time outdoors, all-consuming play, human touch, and deeper social connections.” Sisson, 60, lives in Malibu, California, and still sports a tan, taut torso. You have to forgive the awkward overuse on his website of an invented mascot named Grok—a spear-brandishing Neanderthal often chased by saber-toothed tigers—to appreciate his efforts at grounding his program in real science.

In a preamble, Sisson offers a basic but still engaging primer on the growing field of epigenetics. As Sisson puts it: “Epigenetics explains how controllable environmental factors—the food you eat, the sleep you get, the exercise you do, the amount of sunlight you’re exposed to, the social interactions you have, and even the thoughts you think or how much you laugh at a joke—trigger gene expression in different biochemical ways.” For example, a 2009 study published in Life Sciences Journal found that laughing switched on genes that helped lower blood glucose levels in patients with type 2 diabetes.

Epigenetics is just beginning to sort out the complex molecular symphony that takes place when humans interact with their environment. But as Sisson smartly points out, there is enough data available to lay out a few cautionary tales—like how certain foods, coupled with inactivity, can give rise to disease-causing cellular mutations—as well as to provide some beneficial tips, like how moderate levels of sun exposure can help prevent melanoma.

In one now familiar trope, he explains how marathon bouts of sitting signal genes to turn off the hormone leptin, which controls fat metabolism. After that happens, even an hour on an elliptical trainer can’t counter the effects of sitting at your desk all day, giving rise to “active couch-potato syndrome.” Take frequent breaks and move around, he urges, and get a standing desk to create a stand-sit cycle during your workday.

The Primal Connection is a follow-up to Sisson’s well-received 2009 book, The Primal Blueprint, which focuses on dietary recommendations, along with some general exercise Rx. In Connection, he clearly wants to provide us with an expanded program that encompasses more general lifestyle factors and healthier alternatives to our increasingly static, screen-centric lives. Some of it is illuminating, like how contact with dirt, or more specifically Mycobacterium vaccae—bacteria commonly found in soil—prompts the release of serotonin, a hormone that quells anxiety.

Sisson’s recommendations: work in your garden, stomp through a creek, lie in a field, or sign up for a mud run. Other sections, however, are more suspect, like the one pointing out the “serious health risks of using the everyday toilet.” He’s not talking about the hygienically challenged dude who used it before you, either. He’s worried about “fecal stagnation” due to inefficient evacuation caused by sitting on the throne. You should be squatting instead.

For neophytes who need some guidance shifting to paleo, Jason Seib’s The Paleo Coach offers straightforward how-to help, from tweaking your mindset to laying out a monthlong meal plan. Seib is a personal trainer who runs Clackamas Physical Conditioning in Oregon, and despite the title’s performance-related overtones, The Paleo Coach is really intended for a general audience. Seib makes two assumptions: that paleo is the “natural human diet” and will help you lose weight and improve your health, and that you’re going to have a tough time sticking with it, since giving up grains and dairy is a seismic nutritional shift for most Americans. “There are only two reasons people fail,” Seib writes, “lack of good information, and lack of motivation.” He does a good job providing both.

The Paleo Coach embraces the rote physiology espoused by the paleo community—that we’re maladapted to the modern high-carb diet, and that we need to convert to a predominantly meat-and-veggie meal plan—but Seib’s efforts to motivate us to do so are fresher and more compelling than the usual paleo lit. He spends the first third of the book drilling on the reasons we want to change our diet, trying to nudge readers away from the compulsion to get a hot body and refocus on being healthy; the beach physique, he contends, will follow.

As CrossFit and related gyms have mush­roomed, the paleo phenomenon has embraced new training modes that emphasize mobility over muscularity. This is the gist of Kelly Starrett’s excellent Becoming a Supple Leopard. Starrett is a physical therapist and CrossFit trainer in San Francisco with a popular series of instructional videos online at MobilityWOD.com. Training for mobility, he believes, has ushered in a new human-performance epoch. “Eating, sleeping, and moving correctly are not gimmicks or fads,” he writes. “The dam is burst and the personal biological revolution is here.”

Starrett’s supple-leopard metaphor is meant to imply that humans can attain similar levels of dynamic movement through appropriate coaching. Starrett’s training plan is about progressive conditioning, cultivating joint and spine flexibility in combination with muscle torque, power, and endurance. Make no mistake, Becoming a Supple Leopard is a technical book, stuffed with illustrations and mobility exercises with vaguely S&M–sounding names, including “banded flossing,” “paper clipping,” and “flexion gapping.” But, as textbooks go, it’s a lucid, inspiring, and insightful season pass to improved performance.

Along with its many champions, the paleo phenomenon has attracted plenty of critics. Among the most prominent is Marlene Zuk, a biology professor at the University of Michigan. Zuk, whose book Paleofantasy: What Evolution Really Tells Us About Sex, Diet, and How We Live, contends that paleo enthusiasts often play fast and loose with the facts of life during the Pleistocene. The belief that we once existed in an evolutionary sweet spot—­cavorting (and noshing) in harmony with our environment—is pure nostalgia, Zuk says. She argues that there wasn’t a single ancestral diet but many. Further, she insists, paleos are misguided in their assumptions about evolutionary change. “We cannot assume that evolution has stopped for humans,” Zuk writes, “or that it can take place only ploddingly, with tiny steps over hundreds of thousands of years. In just the last few years we have added the ability to function at high altitudes and resistance to malaria to the list of rapidly evolved human characteristics.”

Another prominent player taking issue with the paleo prescription is T. Colin Campbell, author of Whole: Rethinking the Science of Nutrition. Campbell, the Jacob Gould Schurman Professor Emeritus of Nutritional Biochemistry at Cornell University, is best known for his 2005 book The China Study, which builds a strong case for an entirely plant-based diet to ward off disease and nurture optimal health, based on the findings of a 20-year study of rural Chinese eating habits and chronic disease.

Whole continues the China Study argument. Campbell (somewhat conspicuously) avoids terms like vegetarian and vegan, but he advocates, in a nutshell, getting 80 percent of your calories from plant-based carbohydrates, 10 percent from fat (from sources like avocados and coconut oil), and 10 percent from protein (from nuts and seeds). He considers meat-heavy meals—he never cites paleo by name—to be a delivery system for carcinogens and other disease-causing elements.

While Whole and the growing library of paleo-themed lifestyle manuals seem to be diametrically opposed to one another, they actu­ally aren’t so very different. What they all advocate for is a more mindful awareness of daily behavior. This is largely dietary, since eating is our common denominator.

But it’s also expressed in our ratio of stasis to movement, our exposure to our environment, and, ultimately, our connection to each other. The messages are surprisingly similar: We’ve lost sight of something, maybe many things, that are essential to living full, healthy lives. And despite all the technological advancements of recent decades—the important tools and the awesome toys—we need to make some serious adjustments soon, or we won’t be well enough to enjoy them.

When core body temperature is within normal range, your muscles are poised to perform. Overheat, and the body, fearful that you are going to cook your core organs—heart, lungs, liver, kidneys, and brain—sends your blood towards the surface of your body to cool. Overheat, and not only does fatigue set in, but strength, endurance, and cognitive functions fall apart with the lack of blood where it counts. (Your muscles need blood to deliver oxygen and nutrients, and to clear out metabolic waste like lactic acid.) Send all the blood to the skin, and those blood functions are put on hold.

All mammals have specific heat-dissipating strategies: dogs pant, dumping heat through their tongues; rabbits “sweat” through their ears. In humans, hot blood travels to the skin, but particularly in the palms and soles of the feet. When an athlete gets hot, blood flow naturally increases through these skin regions to them.

Two Stanford biologists reasoned that if they could cool blood at one of the spots closest to the body’s surface without causing vasoconstriction—which shuts down capillaries and prevents the blood from being cooled—they could keep more blood in the muscles where it can help the athlete perform.

Simple surface cooling didn’t work. Jamming an athlete’s hand into a bag of ice or misting him with cold water made the sweaty runner, cyclist or football player feel cooler, but the instant and dramatic cold shut down natural heat dissipation.

Heller and Grahn discovered that by controlling temperature and using a gentle vacuum, they could bypass the vasoconstriction and reduce an athlete’s core temp during exercise, while also minimalizing his cramping and dehydration post workout.

The CoreControl glove has been shown to bump performance during activity by 20%, while also speeding recovery time. It’s currently being worn by the San Francisco 49ers and Golden State Warriors, as well as Stanford University’s football team, whose players even use it during games.

Current drawbacks: It’s bulky—so you have to sit to use it, and it requires ice—two issues the Dynavision team is working to remedy. ($895)