Bipedal Apes in Sedentary Time

By: Emma McDonell

obesity-evolution-630x300Professor Adrienne Zihlman relaxes into the desk chair, her mouth curves into a wistful smile and her eyes light up as she recalls the day her first “fantasy silverback gorilla” died from a freak heart attack. It’s not that she was happy per se that San Francisco Zoo’s prized gorilla, “Bwana,” had met an early end, but a young male gorilla specimen was just what she had been waiting for to begin a project on comparative ape anatomy. It was Labor Day weekend of 1984 when Zihlman was alerted that Bwana was dying. She immediately started making phone calls and a few hours later was on her way to “save” Bwana’s invaluable flesh from the hazardous-waste dumpster. She arrived just in time to negotiate with a California Academy of Sciences representative who was after the bones: “I’ll give you the skeleton after I’ve taken all the flesh off,” bargained Zihlman[M1] .
Zihlman had been waiting to dissect a silverback for a long time. When the UC Santa Cruz anthropology building was eligible for an upgrade in the early 1980’s, lab-less Zihlman joined the building committee. “I wanted a walk-in freezer and an elevator big enough to fit a full-size male gorilla,” she explained matter-of-factly as we sat at a round table in her anatomy lab. She moved into her dream lab in spring of 1984, a mere six months before getting the call about her dream silverback[M2] .

Zihlman’s lab is a peculiar space. It’s a big fluorescently lit room, centered around a tall table covered with colored markers and large white sheets of drawing paper. Lab coats drape on the chair backs. A poster of “El Copito de Nieve”, the only known albino gorilla to ever exist, hangs beside a floor-to-ceiling glass shelving fixture displaying enough skulls for a great haunted house, ranging in size from the size of a kiwi to a small watermelon.  Plastic baboon, gorilla and elephant masks dangle from a hook adjacent to a life-size watercolor painting of a gibbon skeleton. A couple dozen stuffed toy apes look down on the room from the top of tall filing cabinets – some chimps, some gorillas, some dressed in safari gear. Apparently, stuffed primates are a go-to birthday gift for Zihlman.

Dressed in khakis, a turquoise blazer, and matching earrings, she looks “put together” as my grandmother would say. Though her crisp outfit and straight posture make Zihlman intimidating at first glance, she warms immediately once we’re one the subject of primates.

Zihlman has been moving and shaking the field of physical anthropology since she began her grad school work in the 1960’s under the renowned physical anthropologist Sherwood Washburn at UC Berkeley. Since her days dissecting chimps in the Cal labs, she has been on the cover of both Time and Discover magazines and has served as Vice President of the California Academy of Sciences for a number of years. Zihlman is best known for her daring work examining female roles in human evolution and for her groundbreaking research on bipedalism. Her current venture, a two-decade comparative ape anatomy project is equally radical in its own right[M3] .

Zihlman’s current endeavor is to compare the anatomy of orangutans, gorillas, gibbons, chimps and humans through dissection, looking at what exactly each species’ anatomy is meant to do. While Zihlman is working on the bodies of other apes to understand our entire ape family, in making sense of our family, we can better make sense of ourselves. In our modern urban lives, far from the jungles our ancestors inhabited, we often forget our animal-ness, and often to our own detriment. It is not that humans evolved from apes, Zihlman points out. We are apes.

Humans are part of the primate order, a group of mammals comprising 16 families and about 200 individual species, who all originated from small rodent-like, tree-dwelling creatures in the Cenozoic era, about 65 million years ago[M4] . The primate family today includes a diverse cast of characters. There are the nocturnal slow lorises, who render their bite venomous by licking an arm gland and mixing the secretion with saliva. There’s the mandrill, a baboon who lives in complex social groups wherein the males physiologically respond to changes in their rank in dominance hierarchies through an enlargement or shrinking of their testicles and reddening or fading of facial [M5] skin[M6]. [IY7] And there are the wanton bonobos, close relatives of chimpanzees who are now famous for their liberal sex habits. Bonobos are known to get it on with just about anyone in the family: males on male, female on male, adult and child, in positions that seem even too wacky for the Kama Sutra.[M8]

Other than a common ancestor, what primates have in common is hard to pin down. Carolus Linneaus described four key traits in 1758 that delineated primates as creatures with hands, breasts, a collar bone, and set of flat front teeth for cutting[M9] . Since Linneaus, researchers have continued to tinker with the qualifications for primatehood. They are grappling with the question to this day, mostly because unlike other animal groups, there is no single defining feature. Today, there twelve primate characteristics mostly agreed upon, but each has exceptions. To Linneaus’s list, we’ve added flattened fingernails, extremely sensitive fleshy hands, fingerprints, a poor sense of smell relative to our impressive visual acuity, lengthy pregnancies and infant-rearing periods, and a sizable brain compared to body size, and of course locomotion. It’s thanks to our family history, and of course natural selection, that you can read this small type, feel the smoothness of this page of paper, and cannot smell the remnants of the dog poop you stepped in yesterday on the bottom of your shoe.

 

Zihlman studies a specific sub-group within the Primate order, a super-family in Linnean terms, called the hominoids. The hominoids are a group of tail-less primates with relatively big brains and arms that are shaped differently from legs who diverged from the rest of the primates 30 million years ago (mya[M13] ). The hominoids split apart into two families, the gibbons, known as hylobatidaes, and the hominidae, composed today of orangutans, gorillas, chimps, bonobos, and the humans. The orangutans broke off from this group a while back, about 14mya, leaving a sub-family of related individuals called the homininae. Not long after the gorillas diverted, leaving the human lineage and chimps together under the banner hominini. Finally, around 10mya, in a move that would have drastic consequences for all species across the planet, the chimps and the homo lineage split apart, sending each species off to adapt to different environmental niches, and become completely different animals.

The terminology of the hominoids is confusing, but that’s the point. All of these creatures are very closely related. Chimps and humans could be compared to siblings, while gorillas could be considered a sort of cousin. Gibbons are that group of people at a family reunion who you’ve never actually met, but have distinctly similar facial features and ways of talking to your own. Zihlman is working to understand both the similarities amongst all the hominoids, and what sets each species apart.

 

Evolutionism’s two main vanguards, Charles Darwin and Thomas Huxley, were the earliest proponents of comparative anatomy, making extensive use of skeletal comparisons in constructing the concepts of evolution and species relatedness described in Darwin’s An Origin of Species. It was Huxley who constructed the famous diagram “Evidence to a Man’s Place in Nature” in 1863 – depicting the human skeleton adjacent to chimp, gorilla, orangutan, gibbon skeleton – to show the biological intimacy between apes and humans, a heretic notion in his day. But for all Darwin and Huxley’s genius, they completely overlooked the guts of the matter.

It may seem intuitive to study both flesh and bone to understand anatomy, but Zihlman’s emphasis on the whole body and dissection makes her an iconoclast in the field. Physical anthropology has myopically focused on hominid bones and brains since the field’s beginning, overlooking the other 60-70% of body mass. While fossils recurrently make the cover of Time, and ape intelligence studies abound – recall the household names Leakey and Goodall – relatively little is known about the muscles and ligaments – the meat, shall we say – of our hominid relatives. In throwing out the flesh and ignoring the habitat context in which apes evolved, researchers are literally left with a skeleton of the available data, perhaps missing valuable insights into still-debated questions about human evolution.

“It’s hard work finding ape specimens, especially the males,” explains Zihlman who has now dissected an unprecedented five silverback gorillas, four “orangs”, innumerable chimps, and many gibbons. Most of the time zoos dump the flesh and ship off the bones to be made into skeletons, spending their afterlives on museum shelves. A self-proclaimed “ambulance chaser”, Zihlman expends lots of energy networking with zoos and conservation organizations across the nation, but the hassle is well worth it for the insights into the hominoid family that she can’t get from any other technique[M14] .

Today, we have sophisticated DNA technologies to cross-examine pre-existing evidence of human evolution and numerically define species linkages by comparing  genomes. But there are limitations of these increasingly exact, increasingly narrow ways of knowing. Consider the oft-touted statistic, that we share about 95% of our genes with chimps. It seems remarkable until we learn that humans also share 90% with lab mice and 85% [M16] with a zebrafish[M17] . Zihlman’s project pushes against “quantitative, pseudo-science” skeletal analyses of anatomy to see each creature as a whole being, adapted for a certain niche in a certain environment.

Zihlman’s project focuses on locomotion strategies, because as she puts it, “locomotion underpins everything.” It’s the arms and legs that propel an animal toward food, to find mates, to avoid predators. You name it, the locomotor system enables it. “Anatomy underlies behavior,” she explains.

Much as only a mechanic really knows cars, you can’t know a species without a thorough understanding of how the creature’s mechanics work. “It’s essential to understand the underlying infrastructure to understand the species,” explains Zihlman. “It’s not just about seeing that they’re running through the trees, it’s understanding the equipment they have to run through the trees,” she says, pointing to a poster of what looks like a human skeleton with its arms stretched to the ground.

“We all come from the same basic plan,” says Zihlman: “It’s understanding the precise adaptations that’s important.” It’s the small tweaks in the locomotor systems that make huge differences in how we live our lives[M18] .

Zihlman opens a thick binder full of laminated pages, which I soon learn is the beginnings of her new book. She flips to a page depicting a skeleton with salmon-colored muscles lightly painted over the bones and percentages of the individual mass inscribed adjacent each muscle. As I look closer, I see the skeleton is split down the center; it’s half silverback gorilla, half male orang. At first, the two halves look fairly similar to me, two big-bodied primates. But after ten minutes of Zihlman explaining the differences, I can’t even see the similarities.

“They’re about the same total mass, but the mass is in totally different places,” Zihlman begins. “To put it shortly, the orang’s all arms and the gorilla is just the reverse[M19] .”

The orangutan, or “man of the forest” in Malay, is an acrobat, equipped for life high in the fruit-laden forest canopies of Sumatra and Borneo. He’s got muscular arms stretching twice the length of his legs, enormous hands and feet, and bendy joints all over.

“The ‘orangs’ have such a high center of gravity,” Zihlman explains, lifting her arms above her head and slowly tilting her torso to demo. “When they cross gaps in the trees they just kind of leeeean over,” she continues, dragging out each syllable to emphasize the leisurely pace of orangutan movement[M20] .

“And his fingers are as long as his tibia!” Zihlman exclaims, springing up from her chair to rifle through a filing cabinet. She returns holding what looks like a human hand, except the fingers are each about a foot long and the phalanges are as thick as a wine cork.

“Oh, and their feet: they are not meant for walking,” she says, retrieving an orangutan foot from the same drawer and placing it sideways on the table. It looks almost identical to the orangutan hand, with long, thick phalanges and an opposable thumb or in this case, toe. The feet are like extra hands, adept at grasping branches. “They walk putting pressure on the outside of the foot.” Try this and you’ll see why they rarely come down from the trees.

The orang’s gymnast body is specialized to satisfy his mostly frugivorous diet of jackfruit, durian, and any of the 400 other types of food orangs are known to eat[M21].

The gorilla on the other hand is king of the forest floor. There are two species of gorilla, Eastern and Western, each with two subspecies, and they’re all “built for propulsion”. Gorillas have “bulky” quads and shoulders, allowing them to run quadrupedally across uneven forest floor at speeds reaching 25mph [M22] [M23] .

Gorillas have broad, flat hind feet like doublewide human feet and thick knucklebones meant to be pounded into the ground at a full run. Gorillas do climb trees, but they climb slowly and carefully, taking precautions as they ascend, staying close to the trunk and far from risky branches [M24] .

Like orangs, gorillas are casual vegetarians, focusing on plant material foods, but occasionally indulging in an ant-covered stick. Gorillas are experts on the mostly fibrous foliage available on the forest floor, consuming up to 60 lbs of mostly plant materials each day [M25] , due not in small part to their agile frame. They eat bamboo, barks, leaves, ants and berries, over a hundred plant species and are very particular about which part of the plant is edible.

Each species has its staple foods, but what sets ape diets apart from other animals is our lack of focus. Apes are “generalists,” says Zihlman [M26] . Like mobile compost bins, we can digest just about anything, which is really quite impressive considering that most mammals are strict carnivores or herbivores. Adaptible and unrestricted, we’re “opportunivores”.

Similarly, apes stand out for our locomotor flexibility. Orangs can walk bipedally for short distances, and gorillas can brachiate cautiously, and humans can climb. We’re made to make do.

So what sets humans apart from our ape brethren? “We’re long distance walkers, we’re bipeds,” declares Zihlman without a second thought. Chances are you don’t reflect daily upon how lucky you are to have the locomotor system you have, but try thinking of what you would do without it. No legs, no wheelchair. 24 hours. Go. Could you make breakfast? Did you make it to work? Answer the phone? How long did it take? Locomotion is no trivial matter; it’s the framework that allows animals to live the way they live. And for humans, it’s our gait that defines us.

The last common ancestor we had with apes was the forefather of chimps and humans. This creature, neither fully chimp nor fully human, lived about 7-8 million years ago, at the tail end of the balmy Miocene epoch. Much of Africa was blanketed in tropical forest at the time, and the primate order was multiplying, consisting of many more species than are alive today[M27] .

A small group of these African apes descended from the forest canopy to split their time between the trees and the forest floor, and started walking upright. The reason(s) for this transition are hotly debated, but all the theories point to food sources as a factor. “Chances are it was multi-factoral; one theory is not right and the others wrong… that’s just too simple,” says Zihlman. Plus, chances are we’ll never know. The tropical environments these creatures inhabited had extremely acidic soils, dissolving any bones long before they could even begin to fossilize.  But this transition was consequential in magnitudes difficult to fathom, as their shift onto two legs was what set in motion the divergence of the Homo, or human lineage, from the [M28] chimpanzees.

Fossil evidence of the earliest potential candidates our first distinctly bipedal ancestor around 7 million years ago is meager, but we can tell from fossil fragments that these apes had bipedal locomotion or upright posture, that their brain size was comparable to that of a modern-day chimp, and that there was not a single bipedal ape but many, each adapted to a slightly different environmental niche. There was Sahelanthropus tchadensis from 7 mya, Orrorin tugenensis from 6 mya, and Ardipithecus kadabba from 5.5 mya [M29] .

Over the next few million years, armed with legs for walking and a flexible diet, the Homos migrated out of the forest and into the grasslands. Luckily for scientists, this new habitat’s soil preserved crisp fossils.

The earliest clearly proto-human fossils come from the East African Rift Valley, an area stretching from Turkey all the way to Mozambique where tectonic forces are literally ripping the continent apart, exposing millions of years of rock, and millions of years of human history. This area was also where the first Homos lived. In fact, there are areas where you can literally see back in time as you look down the canyon at multimillion year old rock layers [M30] .

The fossil record becomes very rich when the Australopithecine show up around 4 mya. Best known by the “Lucy” skeleton found in the 1970’s, the five known species of Australopithecine all lived in the savannahs and grasslands of East Africa around the same time.

Based on their pelvis shape, the Australopithecine were clearly bipedal. “There is only one group that has an ilium like ours and that’s the really early hominids. Everybody else: the apes, monkeys, ungulates, insectivores, everything has a different shaped-pelvis,” explains Zihlman. A slight broadening of the ilium, the bone forming the upper part of the pelvis, was the first domino to fall, propelling the Homos to separate from their kin in the trees [M31].

But the transition from arboreal life to upright walking did not occur in a single step. The Australopithecine anatomy was hybrid ape-human, making their stride not nearly as graceful as us seasoned bipeds. “For one thing, they didn’t have trunk rotation,” explains Zihlman, who did biomechanical analyses of Australopithecine pelvises and chimp pelvises to determine how the Australopithecine walked. The Australopithecine were stout creatures averaging 4 feet in height and 80 lbs, and some evidence suggests that while principally bipedal, they periodically spent time in the trees. Australopithecine could walk, but they were no eggheads. In fact, based on their puny brains, a protruding brow bones, minuscule neck and nonexistent waist, early hominids probably looked more like an upright chimp than a modern human [M32] .

The anatomical tweaks that propelled bipedalism seem minute: a slight broadening of the ilium, a knee that can fully extend, a curved lower spine — but it was these changes that made Homo Homo. “Bipedalism changed everything,” says Zihlman. It’s thanks to our upright stance that we have manual dexterity, unhampered by bulky knuckle-walker hands.  Bipedalism was the original key to the success of our forefathers, allowing them to carry long distances, to throw, to run, to do things with their hands while running, to gather the extra food sources that supported an increase in brain size, and to eventually spread all over the planet [M33] .

A second trait that allowed us to spread and thrive in new places was that we are not picky eaters. “The dietary diversity of the hunter-gatherers is quite impressive,” says bioarchaeologist Dianne Gifford-Gonzalez, who studies animal bones for evidence of past human diets in the same UC Santa Cruz anthropology department as Zihlman. “Compare human diets to just about any other mammal and there’s just no comparison.” We made do. In Arctic regions, diets consist mostly of blubber and no plant foods with an average of 95% fat while the natives of California ate a multitude of species including shell fish, seeds, nuts, berries and game, depending on the season [M34] .

The combination of legs for long distance walking and an adaptable diet were essential in making humans one of the most successful invasive species on the planet. “How do you think humans spread across the planet? We didn’t get there by boat, airplane, train car. We walked!” exclaims Zihlman. “In just a few thousand years, the Homos colonized Asia, Australia, Europe.” The fact that our species is characterized by its ability to move long distances and eat anything seems quite odd considering our stationary carbohydrate-loaded modern lives. In many ways, human life is incredibly comfortable and leisurely compared to the lives of our hunting and gathering ancestors. However, the human body was not constructed for life on the sofa or daily drive-thru meals, and the impacts of modern lifestyles are evident in the mushrooming of the diet-related diseases, many of which were non-existent in past societies [M35] .

We are living in an “alien ecology” says anthropologist Richard Deacon. “It’s as though we’ve been taken out of the context we evolved in and stuck into a very strange environment,” he explains in his acclaimed Human Evolution course at UC Berkeley. For the vast majority of our evolutionary history, we were hunting and gathering, subsisting on diverse diets and walking everyday. Today, we’re doing neither.

The advent of agriculture some 10,000 years ago is the main cause for our dietary simplification. Whereas hunter-gatherers collected many types of food based on availability, farmers grew just a few crops and accumulated stores so they could eat these same foods after harvest season was over. Now 10,000 years may seem like a long time n relation to our lifetime, but it’s a mere blink in evolutionary time. We spent 99% of our history living as hunter-gatherers meaning we also spent 99% of our history adapting genes to digest hunting and gathering diets. So if hunting and gathering can be seen as our “state of nature,” the question is, has 10,000 years been enough time for our bodies to adapt?

“Essentially, the whole bottom part of the food pyramid was nonexistent before agriculture,” says Gifford-Gonzalez. Agriculture introduced starch as mainstay in the human diet. Rice, wheat, corn, potatoes, cassava, and sorghum, were all domesticated by early farmers from wild strains [M36] .

Soon, the breadth of human diets plummeted. It was not unusual for hunter-gatherer groups to utilize over a hundred different species for food, much like our gorilla and orang relatives. The world has over 50,000 edible plants yet, three of them – rice, corn and wheat – provide 60% of the world’s food energy intake [M37] .

It seems that all of our favorite foods – potato chips, cake, cookies, bread, french fries, pasta – are bad for us. High fat, high sugar foods in hunter-gatherer societies were fruits and nuts, foods chock-full of nutrition. We have inherited taste buds with proclivities for the sweet and fatty; hence the delicious smell of baking cookies and the satisfying crunch of Doritos. Unfortunately for us, these foods aren’t rare finds on day-long food collection journeys; rather, they crowd our fridges, pantries, supermarket aisles and convenience store shelves, leaving us in a constant battle between what we crave and what’s good for us.

If a complete reorganization of the human diet wasn’t enough of a shocker to our system, we hit it with a second blow over the course of the last century. We stopped moving. Well, kind of.

For a number of reasons, humans are moving much less. Long gone are the long days of hunting and gathering for meals. Now we just pull up to the drive-thru and hand over a twenty.

A second locomotor transition around the turn of the 20th century was a big part of this. After spending millions of years fine-tuning our bipedal gait, we traded our legs in for autos. In 1920, one in every 14 Americans owned automobiles, and today the average American household owns 2.28 cars [M38] [M39] . Just as our bipedal locomotor system underpinned the way we lived our lives in the past, our modern transportation systems enables our lives today.  We drive more and more each year; to the store, to the bank, to work. And we’re training our offsring to do the same. 42% of school children walked to school in 1969 today that number is less than half that about, a mere 16%.

In addition, our daily lives used to involve rigorous physical labor, but today movement is called “exercise,” this extra thing some people do in their spare time. In the US, sedentary jobs have increased 83% since 1950, and the amount of time spent sitting increased 8% in just 20 years between 1980 and 2000. Our bodies are built to move, and we’re not moving [M40] .

“What we’re seeing now is people making the transition from doing a lot of physical labor, either working in their own fields or working for other people, working on the railroad, working in factories where they’re really using their bodies to not using their bodies very much, but eating the same food because that’s what they’re used to,” explains Gifford-Gonzalez [M41] .

The ramifications of the mismatch between our biology and the environments we inhabit are easy to see. Sixty five percent of American adults are obese. The three leading causes of death in the US — heart disease, cancer, and strokes — are all linked to diet and exercise. The clash of our biology and our culture is killing us [M42] .

But not everyone is rotting away on la-z-boys, stuffing their faces with processed carbs. Millions of people are fighting their sedentary fate with gym memberships, cardio-kickboxing, Zumba, Tae Kwan Do, Bikram Yoga; anything that might make movement fun. Similarly a new diet plan seems to mesmerize Americans each year, only to slowly fizzle out as people give up on stringent off-limits lists and point systems. Americans fork out 35 billion dollars per year on diet products desperately searching for the one magic diet [M43] .

Within all the exercise and diet mumbo-jumbo, one growing trend stands out as a potential cure in its credo of addressing health from a human evolution standpoint. Crossfit is a “lifestyle” plan based loosely on the idea of aligning diet and exercise with our evolutionary adaptations. “We do stuff your body’s meant to do,” explains Austin Einhorn, an exuberant member of a Crossfit gym in Santa Cruz, CA, where the whole movement started back in 1995. “It’s like a cult, and it all started in Santa Cruz,” he explains. Einhorn’s an ideal representative of Crossfit. At 6’5”, with pecs popping out of his t-shirt and globular shoulders, his towering presence is a paragon of human fitness, with the exception of the unexplained pain he has in his “right shoulder or bicep.” He’s been doing Crossfit for two years and doesn’t plan on stopping anytime soon.

A self-proclaimed “functionalist,” Einhorn lives by the mantra: “constantly varied, high- intensity, functional movement.”  Crossfit uses free weights, calisthenics, pull-ups and kettle bells, and is based on the Crossfit mantra, “constantly varied, high- intensity, functional movement,” essentially doing “what we would do in he wild [M44] .”

Crossfit workouts, which are often named after women, may seem like punishments to the rest of us.  The Mary involves five handstand pushups, ten one-legged squats, and fifteen pullups continuously for 20 minutes. The Sarah might be even more grueling, involving heaving a 20lbs ball against a wall, “sumo squats” with 75lbs dumb bells, jumping onto 20” tall boxes, bench pressing 75lbs and finishing off with a 500m sprint. “Half way through, you wonder why in the world you ever choose to do this,” says Einhorn. “But once it’s over, there’s no better feeling on Earth.”

According to Einhorn, these caveman feats are what we should be doing. “Our body wasn’t designed to do the same repetitive motions over and over. “Cross-fit prepares you for the real world.” A “real world,” involving spear hunting and nomadic latitude-changing migrations, that we no longer live in. About 80% of people who try Crossfit never return, but the 20% who do can’t seem to get enough.

Today, there are over 450 Crossfit gyms worldwide, and its following is growing rapidly thanks to the interactive website with daily YouTube video posts of workouts of the day, or ‘wods’ as Crossfitters say, people can do in living rooms and garages. Videos often bring in over 200 comments ranging from affirmations, to detailed descriptions of “sore quads” to stopwatch times.

The Crossfit lifestyle combines militant exercise with equally vigorous dieting. “We’re actually in the middle of the ‘Paleo Challenge’ right now. Everyone’s tested before and after and we take before and after pictures, so we all go through it together,” says Einhorn [M45] .

“Everyone’s on either Zone or Paleo,” says Einhorn, later estimating 40%. “You can’t go to a Crossfit gym and not talk about diet, everyone’s comparing recipes and tips.” Crossfit advocates two diets: Zone and Paleo. In Zone, you can eat as much as you want in the correct proportions, 40:30:30 carbs:proteins:fats. This means measuring you eat down to the gram and charting it on a Zone grid. The Zone diet chart Einhorn showed me took me back to high school algebra and my eyes glazed over. Each person has a different “block” requirement. Blocks are either 7 grams of protein, 9 grams of carbs or 1.5 grams of fat. So if I allow myself two blocks for breakfast I can either have 14 grams of protein or 1.5 grams of fat and 9 grams of carbs. In Zone, diet becomes an algebra equation and a science experiment [M46] .

The other Crossfit diet, Paleo, is based on a quasi-back-to-the-land ethic requiring canine-like meat consumption. “We weren’t meant to eat all these processed carbs. We’re essentially putting our insulin levels on a daily rollercoaster,” says Einhorn. The Paleo diet is based on the idea that the human body should only foods available in the Paleolithic era, meaning pre-agriculture. No grains, legumes, dairy, refined sugars, salt or processed oils. What’s left is mostly fruit, nuts, and a whole lot of meat. “It’s what our ancestors did,” says Einhorn. Unfortunately, this diet may exclude more than it includes: “It’s almost impossible to go out to eat,” says Einhorn, “something’s bound to have gluten.”

Yet the popularity of Paleo is mushrooming. Einhorn and his Crossfit buddies have a monthly “Paleo potluck” where they bring dishes and share recipes and diet tips. Paleo-dieters now can choose from whole market of Paleo products on the web including reheatable Paleo dinners, Paleo beefsticks, and even grain-less, sugar-less, processed oil-less cookies.

“I went from Paleo to Zone to Zone-Paleo to Paleo with portion control to take off some weight. Now I’m back on straight Paleo to bulk up my muscle.” Einhorn’s discipline is impressive. He’s been Crossfitting six days a week, sometimes twice a day, and bouncing in between Zone and Paleo for two years now. And he’s not unusual amongst Crossfitters. The Crossfit lifestyle isn’t a yo-yo diet or a quick fix to “shed a few pounds for swimsuit season,” says Einhorn, “a whole lifestyle improvement is what we’re going for.”

But the Crossfit/Paleo lifestyle may reflect a caveman fantasy and a broader societal obsession with diet regimens than anything. The hunter gathers didn’t eat one specific diet; they ate whatever they could find.

“The challenge is to think about what we can take from that ancient history, and it’s really nothing specific,” says Professor Zihlman. As primates, we’re generalists by nature, known for versatile and diverse diets. We don’t really know the exact nutritional magic in fruit and vegetables, we just know they’re good for us. “Eat your colors, eat low on the food chain, and eat a variety,” says Zihlman. There was no single hunter-gatherer diet and no single primate diet, it’s the flexibility that makes us special.

“We can eat just about anything,” says Gifford [M47] -Gonzalez, “but once the variety goes down and the starches up, we see the ‘diseases of civilization’.” Gifford-Gonzalez’s advice for our gathering in the supermarket aisles: “If you can’t picture it growing, don’t put it in your mouth.” Gifford complicates her recommendations by adding that certain ancestries are better adapted for different diets. For instance, Arctic peoples who lived for thousands of years on high-fat diets start eating typical modern diets and acquire diabetes almost instantly. “Their bodies haven’t had as much time to adapt to heavy starch available at the market.” But it’s the inextricable linkage of diet and exercise that are both the problem and solution.

It’s not a surprise that exercise is good for us, but the more we study it, the more we see it may be the ultimate preventative medicine. Heart disease, blood pressure, cancers, diabetes, osteoporosis, back pain, arthritis, depression, colon cancer, breast tumors, weakened immune system, all of these ailments can be avoided by moving more.

New research is even linking mental faculties to exercise. Most recently, a study on Alzheimer’s Disease, an incurable devastating ailment in which people lose memory and a sense of self, found that the disease can be avoided by routine exercise. However, the study participants who walked or jogged daily reaped the benefits, while those who did exercise but less regularly did not [M48].

The conclusions of this study aren’t a surprise for Zihlman, “Our brains need the oxygen!” the daily walker cries. The benefits of exercise are not linked to any single activity, it’s just getting out and moving that’s important.

Zihlman warns against the exercise zealotry of Crossfit, which she says does not even remotely mimic the lives of hunter-gatherers. “It’s really just about getting out and moving,” she explains. “There is no single exercise regimen, walking, running, swimming, getting your heart rate up and limbs working is what matters.”

We evolved to be distance-walkers, and spent millions of years evolving bodies fine-tuned for moving, and yet today we have stopped doing what it is that makes us human. We’ve used our mental abilities to think our way out of exercise with online shopping, automobiles and grocery stores, and cubicle jobs, but our couch lives are killing us.

After all this talk about primates, I decide to visit our family members at the San Francisco Zoo. — another group of primates in a 21st-century alien ecology.

Strolling the winding paths, passing cages filled with beings of all shapes, sizes, colors, and locomotor systems can feel like walking on atop an enormous Linnean taxonomy diagram. A haphazard amalgamation of the best, brightest and cutest Anamalia has to offer are loosely categorized by orders, families, or at least geographical region. Humans, the species that built the arc in the Bible, always stand on the outside of the pens, looking in at “Cat Kingdom”, “Bear Country”, and the “Primate Discovery Center”.

As I wind through the concrete paths of the Primate Discovery Center, the primate family tree diagram found in the beginning pages of every physical anthropology textbook comes to mind. If you aren’t familiar with this diagram, just picture a family tree that began 65 million years ago with the common ancestor we all share as the trunk from which the rest of the tree owes its existence. Like an oak tree, a few thick arms that split relatively close to the ground, representing the two primate suborders, Prosimii and Anthropoidea that broke about 40 mya. The Prosimii branch went off to make a family of saucer-eyed, nocturnal, leaf-eating creatures like lorises and lemurs. The Anthropoidea branch split into two families about 30 mya that each radiated out into genera, and finally those genera sprouted the leaves, or individual primate species. The last three twigs on the hominoidea superfamily divide gibbons, great apes and humans, siblings on this primate family tree [M49] .

I enter a hallway of wire mesh enclosures where our obnoxious and adorable twice-removed distant second cousins New World monkeys are yieeking and howling. The New World monkeys or the Platyrrhines (pronounced plat-a-rynes if you have to say it out loud), split off from the rest of the primates when they rafted to America about 30 million of years ago and evolved their own unique characteristics in the jungles of South America. Chirping squirrel monkeys swing by their prehensile tails across rope bridges onto wooden pedestals with dizzying ease. A pair of emperor tamarinds cuddle upon a platform, their handle-bar mustached faces intent as one appears to pull bugs from the other’s head and their baby scampers down a metal pole. Something about the Amazon and South American sun seem to produce good looks in monkeys and people alike. Platyrrhines all have cute flat noses and a “prehensile” tail which serves as a fifth limb to swing through the forest canopy. I take one last look at a jet-black spider monkey staring straight at me, hooting with his mouth wide open like he’s astonished at something I’ve done, and proceed towards my intelligent and not quite as cuddly kin, the Old World monkeys [M50] .

Immediately, I start to see the family resemblance as I enter the area where the Old World monkeys live. A baboon distinctly resembles an ex-next door neighbor. The furrowed brow, the nervous pacing — with the exception of his apple-red booty he’s a dead on doppelganger. The patas monkeys are a team of angry elves; their pointed ears, stern countenance and mini human faces are eerie in their familiarity.

The path steers off into a bamboo-walled passageway leading me to my blood relatives (literally gorilla blood transfusions use human blood). Gorillas to the left, chimps to the right, hominids everywhere; it’s a family reunion. Children line up with their hands against the glass wall and parents snap iPhone pictures of one of the zoo celebrities, Oscar the silverback Western Lowland Gorilla. He sits just feet from the glass, still and dignified. His broad shoulders are back, fists to the ground as his steady gaze keeps watch over the troop. Even if he didn’t have the distinct glistening silver fur, there is no question who’s in charge here.

A playful baby gorilla scampers down the hill to visit mom, tumbling and somersaulting between knuckle-walk skips on his way down. Mom seems tired, but pulls him into her long arms for an affectionate hug. The toddler sits with her for a few moments, then squirms free and frolics back up the hill, looking for better entertainment.

The divide between humans and animals is literally manifested before my eyes at the zoo. The Homos stand on the concrete paths, licking ice cream cones and reading maps pointing and laughing at the tumbling baby gorilla. The glass wall separating us from our quadruped relatives does much more than just protect the humans from the “wild,” it constructs these categories, categories that may only exist in our minds.

We tend to forget that we too have a slot on Linnean diagrams, nestled tightly beside chimps, gorillas and orangutans. It’s unsettling that all of the characteristics considered distinctly human such as our big brain, language abilities and so on, arose from a change in the shape of our ilium. We’ve grown up in a world dominated by humans, and so it’s natural that we consider ourselves as separate from the rest of the planet. We do have this giant brain that allows us to reason and speak complex languages; I am not saying humans are not different. But understanding that we are more similar than different is important for a number of reasons.

In exploring the deep history of the human species and how we came to be, what stands out is not our specialness, but the luck, chance and role of environmental conditions that made us into the species we are.

Eroding the edifice of human exceptionalism and taking a step back to see our species’ trajectory gives us insight into the health problems we face today by pointing to the inextricable linkage between our biology and environment.

We seem to have completely forgotten our animal-ness, neglecting our biological needs for movement and varied diets in favor of lives that are comfortable, but overall bad for longevity. This mismatch between biology and our modern ecology is harming us. Humans may have the ability to reason and create complex systems where we don’t need to do the physical labor our ancestors did, but we cannot reason our way out of our biological injunctions.

As long as orangutans live in jungles, they will live their lives swinging through the trees eating fruit, and as long as we live in habitats of supermarkets and freeways, we will drive cars and eat processed industrialized food. Changing these habits, then, is not a simple matter of a diet plan or an exercise regimen. Austin Einhorn is right, “what we’re going for is a lifestyle change.” Habit and behavior changes are extremely difficult, because as we are animals, we are also products of our environment.

Examination of our evolutionary history reminds us that we are part of the primate family, a group known for our versatility and adaptability. Evolution does not show us a single “natural” or “right” way to be human, but shows us that being human means we have options.

“Movement is absolutely fundamental,” says Zihlman. “All the studies show that you can increase your longevity, mental capacity, avoid cancer if you move more. That’s what we’re about: motion, motion, motion.”

Her dietary advice is similarly broad. “The main thing is to eat as broadly as possible,” says Zihlman. “The health literature is always saying to ‘eat your colors’ because they don’t really know what’s in fruits and vegetables. There are so many different kinds of chemicals working together. And we don’t really know what’s in fish, but it seems to be important. There’s a lot that we just don’t know.” It seems we might be best off giving up restrictive “diets” altogether and trying to expand what we eat rather than limit it. “We know that diet is connected to health, but in a way that’s an extreme because we can survive doing an awful lot of things.”

While acknowledging of our animal-ness teaches us about ourselves, it also pushes us to reconsider our species’ narcissism. While human health and longevity is important, we must also be aware that the environment does not only influence us, we influence it.

In recent years, our impact on natural systems has greatly intensified. As we spread to new, unconquered territories with our technologies and avarice for resources, we push out other species and completely reorganize entire ecosystems.

The success of the homo sapiens is at odds with the survival of our kin. Our last remaining relatives are all dying off due to our gluttony. While the homo sapien population edges towards 7 billion, great ape populations fall to triple digits. Seven hundred Eastern Mountain gorillas are left and just 3,000 Sumatran orangutans. The impending extinctions of many of our closest relatives bring up moral questions about our role as a species. And given our acclaimed reasoning abilities, I think it’s only right we ask them. How do we proceed knowing that the way we live our lives is killing off our greater family? Does our biologic similarity to apes obligate us to take care of their habitats more than other species?

They say that blood is thicker than water, but endangered ape populations indicate otherwise. We are losing our ape brothers and sisters, and in some ways, we are losing ourselves.

Works Cited

Alexander, D. (2010). Primate Locomotion. In H. J. Birx (Ed.), 21st Century Anthropology: A Reference Handbook (pp. 624-633). Thousand Oaks, CA: SAGE. Retrieved from http://sage-ereference.com/view/21stcenturyanthro/n62.xml

Cachel, Susan. (2006) Primate and Human Evolution. Cambridge University Press: NY, NY.

(1920) Cars per person in the USA 1920. Transportation History Sources. Retrieved from http://www.railsandtrails.com/AutoFacts/1920p37-100-8.jpg

Meal Plans. (2004, May) Crossfit Journal. Issue 21. Retrieved from http://library.crossfit.com/free/pdf/cfjissue21_May04.pdf

Crossfit (2008, April 18) History of Crossfit. Crossfit Info. Retrieved from http://www.crossfitinfo.com/history-of-crossfit/

Deacon, Terrence. (2009) Lecture 11: Primate locomotion, feeding ecology, and social systems. Intro to Physical Anthropology. UC Berkeley. iTunes U.

Deacon, Terrence. (2009) Lecture 12:Great apes: Orangutans, Gorillas, Chimpanzees, and Bonobos. Intro to Physical Anthropology. UC Berkeley. iTunes U.

Deacon, Terrence. (2009) Lecture 13: Apes to Australopithecines. Intro to Physical Anthropology. UC Berkeley. iTunes U.

Diouf, Jacques. Food and People. United Nations Food and Agriculture Organization (FAO). Retrieved from http://www.fao.org/docrep/u8480e/u8480e07.htm

Einhorn, Austin. (2012, February 17) Interview. 760-419-1356.

Gifford-Gonzalez, Diane. (2012, 16 February) Interview. UC Santa Cruz. dianegg@ucsc.edu

Great Ape Statistics. The Great Ape Trust. Retrieved from http://www.greatapetrust.org/great-apes/statistics/

Gupta, Sanjay. (2007, September 22) If we are what we eat, Americans are corn and soy. CNN.com. Retrieved from http://articles.cnn.com/2007-09-22/health/kd.gupta.column_1_high-fructose-corn-syrup-corn-refiners-association-soybean-oil?_s=PM:HEALTH

Huxley. Thomas Henry. (1863) Evidence as to Man’s Place in Nature.

Haagen, Klaus D. (2011) Non-Human Primate and Human Evolution. Grzimek’s Animal Life Encycolpedia. From Gale Virtual Reference Library. 299-309.

Hartwell Moore, John. (2008) Human and Primate Evolution. Encyclopedia of Race and Racism. From Gale Virtual Reference Library. 116-121.

(2008, February 25) Kids Walk to School: Then and Now. Centers for Disease Control. http://www.cdc.gov/nccdphp/dnpa/kidswalk/then_and_now.htm

“Learning About Gorillas.” The Dian Fossey Gorilla Fund International Website. Retrieved from http://gorillafund.org/

Leakey, Richard. (1994) The Origin of Humankind. NY, NY: Basic Books

McNamara, Melissa. (2009, February 11) Diet Industry Is Big Business. Retrieved from

http://www.cbsnews.com/stories/2006/12/01/eveningnews/main2222867.shtml

Our Genetic Identity. American Museum of Natural History. Retrieved at http://www.amnh.org/exhibitions/genomics/1_identity/alike.html

Reynolds, Gretchen. (2012, 18 January) How Exercise May Keep Alzheimer’s at Bay. The NY Times. http://well.blogs.nytimes.com/2012/01/18/how-exercise-may-keep-alzheimers-at-bay/

Setchell JM, Smith T, Wickings EJ, Knapp LA. (2008) Social correlates of testosterone and ornamentation in male mandrills. Horm Behav 54(3):365-72.

Swedell, Larissa. (2011) Baboon Sociality. Imfene, part of the South Africa Primate Ecology and Genetics Group. Retrieved from http://www.imfene.org/baboon-biology/baboon-social-organization

Stein, Rob. (2005, November 15) A Daily Workout Could add 4 Years to Life, Study Says. The Washington Post. Retrieved from http://www.washingtonpost.com/wp-dyn/content/article/2005/11/14/AR2005111401051.html

The Price of Inactivity. (2011) The American Heart Association. Retrieved from http://www.heart.org/HEARTORG/GettingHealthy/PhysicalActivity/StartWalking/The-Price-of-Inactivity_UCM_307974_Article.jsp#.T0_LaXKXSGY

Zihlman, A., Underwood, C., McFarlane, R. (2011) Functional Anatomy and Adaptation of Male Gorillas With Comparison to Male Orangutans. The Anatomical Record.  294(11) 1842-1855.

Zihlman, Adrienne. (2012, January 19) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

Zihlman, Adrienne. (2012, February 1) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

Zihlman, Adrienne. (2012, January 8) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

White, Tim D. et al. (October 2009) Ardipithecus ramidus and the Paleobiology of Early Hominids. Science, 326. Retrieved from http://www.sciencemag.org/content/326/5949/64.full.pdf?sid=4d42e252-eacd-470a-bd0f-1f938de10ee5

Russon AE, Wich SA, Ancrenaz M, Kanamori T, Knott CD, Kuze N, Morrogh-Bernard HC, Pratje P, Ramlee H, Rodman P, Sawang A, Sidiyasa, S, Singleton I & van Schaik CP. (2009).  Geographic variation in orangutan diets.  In SA Wich, SS Utami, T Mitra Setia & CP van Schaik (ed.). Orangutans:  Geographic Variation in Behavioral Ecology and Conservation, pp. 135-156.  Oxford:  Oxford University Press.

Why Good Nutrition is Important. (2011) Nutrition Policy. Retrieved from http://www.cspinet.org/nutritionpolicy/nutrition_policy.html

Zimmerman, Jess. (2012, February 23) If People Got rid of their cars, they could afford and extra house. Grist.org. Retrieved from http://grist.org/list/if-people-got-rid-of-their-extra-cars-they-could-afford-an-extra-house/

 [M1]Zihlman, Adrienne. (2012, January 19) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

 [M2]Zihlman, Adrienne. (2012, January 19) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

 [M3]Zihlman, Adrienne. (2012, February 1) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

 [M4]Cachel, Susan. (2006) Primate and Human Evolution. Cambridge University Press: NY, NY.

 [M5]Swedell, Larissa. (2011) Baboon Sociality. Imfene, part of the South Africa Primate Ecology and Genetics Group. Retrieved from http://www.imfene.org/baboon-biology/baboon-social-organization

 

 [M6]Setchell JM, Smith T, Wickings EJ, Knapp LA. (2008) Social correlates of testosterone and ornamentation in male mandrills. Horm Behav 54(3):365-72.

 [IY7]I cut this sentence down to try to preserve some parallel structure in the paragraph

 [M8]Alexander, D. (2010). Primate Locomotion. In H. J. Birx (Ed.), 21st Century Anthropology: A Reference Handbook (pp. 624-633). Thousand Oaks, CA: SAGE. Retrieved from http://sage-ereference.com/view/21stcenturyanthro/n62.xml

 [M9]Cachel, Susan. (2006) Primate and Human Evolution. Cambridge University Press: NY, NY. P.6

 [IY10]I think the go-to primate traits are usually opposable thumbs and binocular vision

 [IY11]removed locomtion because it is non-specific; all creatures have locomotion, and there is not a motion specific to primates.

 [IY12]Although I like the “this page of paper” conceit, since it will be online it seem a little weird

 [M13]Zihlman, Adrienne. (2012, February 1) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

 [M14]Zihlman, Adrienne. (2012, February 1) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

 [IY15]I would suggest changing fancy to sophisticated, elaborate, specialized, or some other word. Fancy sounds flippant- not that I care, but I have personally been critisized for it in the past.

 [M16]Our Genetic Identity. American Museum of Natural History. Retrieved at http://www.amnh.org/exhibitions/genomics/1_identity/alike.html

 [M17]Cachel, Susan. (2006) Primate and Human Evolution. Cambridge University Press: NY, NY.

 [M18]Zihlman, Adrienne. (2012, February 1) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

 [M19]Zihlman, Adrienne. (2012, January 8) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

 [M20]Zihlman, Adrienne. (2012, January 8) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

 [M21]Russon AE, Wich SA, Ancrenaz M, Kanamori T, Knott CD, Kuze N, Morrogh-Bernard HC, Pratje P, Ramlee H, Rodman P, Sawang A, Sidiyasa, S, Singleton I & van Schaik CP. (2009).  Geographic variation in orangutan diets.  In SA Wich, SS Utami, T Mitra Setia & CP van Schaik (ed.). Orangutans:  Geographic Variation in Behavioral Ecology and Conservation, pp. 135-156.  Oxford:  Oxford University Press.

 [M22]Zihlman, Adrienne. (2012, January 8) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

 [M23]“Learning About Gorillas.” The Dian Fossey Gorilla Fund International Website. Retrieved from http://gorillafund.org/

 [M24]Zihlman, A., Underwood, C., McFarlane, R. (2011) Functional Anatomy and Adaptation of Male Gorillas With Comparison to Male Orangutans. The Anatomical Record.  294(11) 1842-1855.

 [M25]“Learning About Gorillas.” The Dian Fossey Gorilla Fund International Website. Retrieved from http://gorillafund.org/

 [M26]Zihlman, Adrienne. (2012, February 1) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

 [M27]Haagen, Klaus D. (2011) Non-Human Primate and Human Evolution. Grzimek’s Animal Life Encycolpedia. From Gale Virtual Reference Library. 299-309.

 [M28]Deacon, Terrence. (2009) Lecture 13: Apes to Australopithecines. Intro to Physical Anthropology. UC Berkeley. iTunes U.

 

 [M29]White, Tim D. et al. (October 2009) Ardipithecus ramidus and the Paleobiology of Early Hominids. Science, 326. Retrieved from http://www.sciencemag.org/content/326/5949/64.full.pdf?sid=4d42e252-eacd-470a-bd0f-1f938de10ee5

 

 [M30]Deacon, Terrence. (2009) Lecture 13: Apes to Australopithecines. Intro to Physical Anthropology. UC Berkeley. iTunes U.

 

 [M31]Zihlman, Adrienne. (2012, January 19) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

 [M32]Leakey, Richard. (1994) The Origin of Humankind. NY, NY: Basic Books

 [M33]Zihlman, Adrienne. (2012, January 19) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

 [M34]Gifford-Gonzalez, Diane. (2012, 16 February) Interview. UC Santa Cruz. dianegg@ucsc.edu

 [M35]Zihlman, Adrienne. (2012, January 8) Personal Interview. UC Santa Cruz. azihlman@ucsc.edu

 [M36]Gifford-Gonzalez, Diane. (2012, 16 February) Interview. UC Santa Cruz. dianegg@ucsc.edu

 [M37]Diouf, Jacques. Food and People. United Nations Food and Agiculture Organization (FAO). Retrieved from http://www.fao.org/docrep/u8480e/u8480e07.htm

 [M38]Zimmerman, Jess. (2012, February 23) If People Got rid of their cars, they could afford and extra house. Grist.org. Retrieved from http://grist.org/list/if-people-got-rid-of-their-extra-cars-they-could-afford-an-extra-house/

 [M39](2008, February 25) Kids Walk to School: Then and Now. Centers for Disease Control. http://www.cdc.gov/nccdphp/dnpa/kidswalk/then_and_now.htm

 

 [M40]The Price of Inactivity. (2011) The American Heart Association. Retrieved from http://www.heart.org/HEARTORG/GettingHealthy/PhysicalActivity/StartWalking/The-Price-of-Inactivity_UCM_307974_Article.jsp#.T0_LaXKXSGY

 [M41]Gifford-Gonzalez, Diane. (2012, 16 February) Interview. UC Santa Cruz. dianegg@ucsc.edu

 [M42]Why Good Nutrition is Important. (2011) Nutrition Policy. Retrieved from http://www.cspinet.org/nutritionpolicy/nutrition_policy.html

 [M43]McNamara, Melissa. (2009, February 11) Diet Industry Is Big Business. Retrieved from

http://www.cbsnews.com/stories/2006/12/01/eveningnews/main2222867.shtml

 [M44]Einhorn, Austin. (2012, February 17) Interview. 760-419-1356.

 [M45]Einhorn, Austin. (2012, February 17) Interview. 760-419-1356.

 [M46]Meal Plans. (2004, May) Crossfit Journal. Issue 21. Retrieved from http://library.crossfit.com/free/pdf/cfjissue21_May04.pdf

 [M47]Gifford-Gonzalez, Diane. (2012, 16 February) Interview. UC Santa Cruz. dianegg@ucsc.edu

 [M48]Reynolds, Gretchen. (2012, 18 January) How Exercise May Keep Alzheimer’s at Bay. The NY Times. http://well.blogs.nytimes.com/2012/01/18/how-exercise-may-keep-alzheimers-at-bay/

 [M49]Cachel, Susan. (2006) Primate and Human Evolution. Cambridge University Press: NY, NY

 [M50]Deacon, Terrence. (2009) Lecture 11: Primate locomotion, feeding ecology, and social systems. Intro to Physical Anthropology. UC Berkeley. iTunes U.

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