Good News, Endurance Runners: One Scientist Says We're Not All Nuts

By: Matt Frazier

The next time your doctor or well-meaning family member tells you running is bad for you, you’ve got an ally.

If you’ve read Born to Run, then you already know his name: Dr. Dan Lieberman.

Image from Dr. Lieberman’s talk, “The Evolution and Dysevolution of Humans”

Dr. Lieberman is the Harvard evolutionary biologist whose theories are challenging the traditional idea that humans aren’t born runners, and the belief that running 13.1, 26.2, or 50 miles at a clip can only do us harm.

Recently, he’s been in the news for his work on barefoot running.  If you haven’t seen the website he and his colleagues put together that shows what happens when runners take off their shoes, you owe it to your legs and feet to watch it.

I had the pleasure of hearing Dr. Lieberman speak at the University of Delaware last week.  Cozy up; this is his exciting take on why humans are, in fact, born to run.  (Please excuse any anthropological botches I make here; I’m a math guy.)

Walking on Two Legs Makes Banana-Getting Easier

About 5 to 7 million years ago, humans branched off from our last common ancestor with chimpanzees and began to walk upright.  As climate change turned lush forests into sparser woodlands, finding bananas to eat became a lot tougher.  (Chimps eat bananas, right?)

You see, walking around hunched over on four legs is hard.  It’s good for climbing trees, but not so good for traveling.  It takes a lot of energy to cover any considerable distance this way.  This is why chimps run only 100 meters a day.  They hate it.

Those who could walk on two legs had an advantage.  They could still climb decently, but now they could travel miles in search of greener pastures.  Or yellower trees.

When Bananas Aren’t Enough

Fast forward a few million years, to about 2.5 million years ago.  Climate change has turned many of those woodlands into plains.  Meanwhile, we’ve evolved to the genus homo, and our big brains now require that we get more calories than we used to.

As bananas (and other fruits and vegetables, of course) become even harder to find, some smarty pants realizes that if we can kill big animals, we can get thousands of calories by eating their flesh, brains, and bone marrow.  (Sorry vegetarians, Dr. Lieberman can’t help us with this one.)  So about 1.8 million years ago, we start hunting.

How to Kill an Antelope Without a Throwing Spear

At this point, we haven’t figured out that we can sharpen something and throw it to become deadly hunters.  And we’re not particularly fast, either.  So how do we acquire all this luscious meat, brain, and bone marrow?

This is where Lieberman’s ideas are new.  He hypothesizes that at this point, we became endurance runners.

Even though humans can’t sprint worth a lick, we’re pretty damn good at jogging, or whatever you call running at 10K pace or even marathon pace.  We can cover these distances much faster than most animals can because we can cool ourselves efficiently.  As evidence of this, four-legged animals are physically unable to pant while they gallop. (Lieberman suggested trying it at home with the family dog; I’ll pass on that one.)

And so persistence hunting was born.  We would wait until the hottest part of the day, head out to the plains in a group, put on our race numbers and stand nervously in line at the porta-pot, and start the hunt.

Here’s how it works.  One person sprints after the prey.  The prey escapes temporarily, but the sprinter stays close enough to point the rest of the group to where the prey is recovering from its sprint.  Repeat a few more times, the prey collapses from hyperthermia, and someone kills it with a rock.

Safe, inexpensive, reliable.  While the prey was doing a deadly interval workout, the group only had to run an easy 15K.

We’re really good at running slowly.  Better than anyone else.  It’s in our blood, and that’s why it feels so good.

The Dysevolution of Humans

The point of Dr. Lieberman’s talk was not to demonstrate that running marathons is healthy behavior.  That’s old news to him, and you can read about it in far more detail in Chapter 28 of Born to Run.

What Lieberman is interested in now is what’s next for humans.  Sure, natural selection turned us into persistence hunting machines.  The problem is that everyone sits around watching Dancing With the Stars and eats at McDonald’s.  Almost nobody lives a “biologically normal” life.  And our technology and medicine have advanced to the point at which people who’d have been the first ones dead in a famine or rough winter a million years ago are today able to live comfortable lives.

Lieberman was careful to point out that he is absolutely in favor of helping people live quality lives, and that to suggest we stop treating them is preposterous.  But he argues that many conditions, like cancer, flat-footedness, and obesity, persist precisely because we can treat them.  A million years ago, people predisposed to these disadvantages would not have survived for long, and natural selection would have removed their genes from the population.

Nowadays, in what Lieberman calls “dysevolution,” their genes are passed on.  Which leads to their offspring having the same conditions.  Which leads to more treatment.  A positive feedback loop ensues.  The reign of natural selection as we know it is over.  What happens next is anybody’s guess.

Dr. Lieberman also spoke a bit about barefoot running.  I’d love to get into it, but that must wait for another post, as this one is getting long.  Check out his barefoot running website for yourself.