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Why Your Gluteus Is So Maximus?

By Alex Linderman
Posted on 02 Jul, 2015

Human bodies are beautifully tuned running machines. But we weren’t built this way originally. Physical anthropologists have shown how our species have evolved over the ages and adopted certain physical traits, traits specifically adapted for running.

Why Run?

So why did early humans run when they could walk?

Archaeological studies at hominid sites offer one strong clue. About 2.6 million years ago, our forebears started eating meat and marrow, to compete with other carnivores for access to the protein needed to grow larger brains.

We know from the earliest sites that early hominids smashed open limb bones of animals killed by predators and extracted marrow. So another possibility is that humans used their swift feet to reach dead mammals before other scavengers. They would have followed clues such as vultures circling in the distance.


Man Vs Horse (And Other Animals)

Humans are considered unaccomplished runners when compared to mammals such as pronghorn antelopes, which can sprint at 40 miles an hour (60 kilometers an hour) for several minutes.

But human running ability is often underestimated. We tend to overlook the combination of our reasonable speed with exceptional endurance.

Not only can humans outlast horses, but over long distances and under the right conditions, they can also outrun just about any other animal on the planet—including dogs, wolves, hyenas, and antelope, the other great endurance runners.


Can A Man Run Down An Animal To Exhaustion?

Through ethnographers' accounts of indigenous peoples, it is conceivable that endurance running helped hunters pursue prey such as deer, antelope, and kangaroos and run them to exhaustion, usually only when temperatures neared 100 degrees F. Essentially, they're pushing the animal to overheat. The animal will eventually collapse, or it will slow down to a point where it just stands there with glazed-over eyes.

During a chase, hunters maintain speeds of around 4 to 6 miles per hour, for anywhere from two to six and a half hours, and traverse up to 22 miles of terrain. These stats fall well within the performance range of the world's fastest competitive marathoners, who set a pace of roughly 12 miles an hour to cover 26 miles, albeit under far less harsh conditions.


Evolution Of The Achilles And Other Foot Tendons

Through fossil records, we can see that early humans in the Australopithecus era did not have Achilles tendons. Likewise, the longitudinal arch of the foot—another well-developed set of springs important to running—appears to have evolved with Homo habilis.

In running, the legs become springs. You land on and compress the entire arch. Kinetic energy from this landing is stored in the many stretchy tendons of the arch and the leg, most notably the huge Achilles tendon. Like rubber bands, the tendons then recoil to launch you into the next step. The presence of the Achilles tendon reduces the metabolic costs of running by half.

You don't evolve big tendons unless you're a runner. Kangaroos, antelope, and other serious animal runners all have a great set of springs, which do nothing for walking. So our tendons can't be explained as being necessary for walking.


How A Big Human Buttocks Helps Running

From the perspective of a vertebrate morphologist, humans lack one of the most obvious features of animals adapted for serious speed: a tail. In creatures that cover ground bipedally, such as kangaroos, and roadrunners, the tail is the major balance organ. In the whole history of vertebrates on Earth, humans are the only striding biped that's tailless. But still, humans turn in remarkable performances.

Without the balancing help of a tail, how do we avoid falling over when we run? The butt, it turns out, is crucial. Chimps and other primates have little buns. In comparison our rear ends are huge. Although few scholars have studied its role in running, the butt is basically a substitute for a tail.

The butt isn't much involved during walking. In running, however, the body leans forward so that each time the leading foot strikes the ground, the trunk wants to topple forward. The gluteus maximus prevents that: It fires just before the foot slams into the floor, creating a braking action that keeps the torso from falling down.


Other Human Adaptations That Have Aided Running

People can shed heat quickly—not by panting, like most animals, but by perspiring through millions of sweat glands. A lack of fur also helps dissipate heat more quickly.

A look into human facial features also shows that our appearance was shaped by selection for running. Compared to our apish ancestors, which could run only short distances, we have a more balanced head, flatter face, and smaller teeth and nose. This shifts the center of mass back, so it's easier to balance your head when you are bobbing up and down.

Similarly, broader shoulders, a narrower waist, and shorter forearms—all characteristic of humans among primates—help the upper body counterbalance the lower body while running. The back and forth pumping motions of our shoulders and arms help counterbalance the head, preventing it from pitching forward on each landing. Simultaneously, with each heel strike, certain shoulder muscles contract and put tension on the nuchal ligament, pulling up the skull and keeping it level.


In a nutshell, if natural selection had not favored running, we would still look a lot like apes. Today running is regarded as a form of exercise. But perhaps a jog in the park goes much deeper than that: It could be affirmation of the very reason that we are human.

Adapted From:
Discover Magazine, May 2006 Issue
Born To Run By Ingfei Chen

National Geographic News, November 17, 2004
Humans Were Born to Run, Fossil Study Suggests by James Owen

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