The Beauty of Our Butts

By Shlomo Maital   

    I am endlessly fascinated by human evolutionary biology – how we have become who we are, through Darwin’s natural selection.  In my next reincarnation, I would like to be like Daniel Lieberman, a Professor of Evolutionary Biology at Harvard University.

    Lieberman was featured on an episode of one of my favorite podcasts, Radio Lab.  The topic:  Human ‘butts’.  Our behinds.  Our gluteus maximus.

    What in the world is interesting about our butts?  A lot.

     It turns out that evolution has given us a precious gift – the ability to run, with the vital help of the largest muscle in our body, our butts.  Here is how Prof. Lieberman explains it:

     “So butts are not only, you know, beautiful, and they’re helping me sit on this chair right now, but—but the butt is, of course, the largest—the gluteus maximus, its technical term, is the largest muscle in the human body. And when we’ve done electromyographic studies, so yes, I have been paid to put EMGs on the rear ends of—of people, and we do it very discreetly and very carefully and modestly, but nonetheless when we do that, what we find is that the gluteus maximus fires twice in every stride. Once and most importantly, and most—to prevent the trunk from pitching forward. So every time you hit the ground when you’re running, your upper body wants to fall forward.   

    “Running is a controlled fall. Very different from walking. And so your gluteus maximus fires just before your body’s about to—your trunk is about to pitch forward and make you hit your nose on the ground, and it helps pull your trunk backward.

    “And the other time the gluteus maximus fires is when your leg is swinging forward when you’re in the air, and it helps decelerate the leg so that you bring your leg down onto the ground. So the gluteus maximus plays a very important role when you’re—when you’re running, and turns out to barely be active when you’re walking. And, you know, you don’t need the fancy equipment in my lab to figure this out. You can just do this yourself at home. Just walk around the room and hold your butt and, you know, clench your kind of butt. And—and when you’re walking your butt will just stay kind of normal, right? It’ll stay kind of, you know …”

     OK.  This is doubtless a lot more than you need or want to know about your butt, right?

     But it’s still amazing, how evolution has shaped us – including the key part we sit on, without which we could not run or even jog, without falling.