Free Body Farm 2 - Flesh And Bone by Jefferson Bass

it from the bottom of your feet all the way up to the top of your head, a distance of five or six feet, or even more. That’s a lot tougher than pumping it three feet uphill, which is about how tall we are when we’re on all fours. It’s interesting,” I said. “To try to compensate for the circulatory problem we created when we stood up, we’ve evolved this complex system of tiny flaplike valves in our veins, whose job is to keep the blood from flowing back downhill in the pause between heartbeats. But as we get older, those little valves tend to leak a bit, so blood pools in the legs, and the extra pressure makes the veins swell up and sometimes burst.”
    An especially tall young woman—she was one of the star players on the Lady Vols basketball team—raised her hand. I pointed to her. “Yes?”
    “So do other mammals—dogs and lions and whales—not have those little valves in their veins?”
    No one had ever asked that before. I had never asked it myself. “To be honest,” I said, “I don’t know. I’ll find out before our next class. Good question.” She beamed; it was considered a coup to stump me.
    “Okay, now let’s talk briefly about the pelvis and the spine,” I said. “Some of you women will doubtless have babies at some point. The good news is, obstetric medicine is getting better all the time.”
    “What’s the bad news?” a female voice called out.
    “The bad news is, babies’ heads are getting bigger and bigger,” I said.
    “Ouch, man,” the same voice said. “C-section, here I come.”
    “Lots of women are having cesareans these days,” I agreed. “Purely as elective surgery, not because there’s any medical complication that calls for it. And frankly, skittish as I am about the idea of having my belly sliced open, if I were a woman, I might consider it, too.”
    “If you were a woman, Dr. Brockton,” called out a guy who had emerged as the class clown, “I don’t think pregnancy would need to be high on your list of concerns.” Much laughter ensued, including my own.
    “Okay, last dumb-design feature,” I said, opening the box I had brought with me. “There are others, but we’ll stop with this.” I reached into the box and fished out an articulated pelvic girdle, the bones held together with red dental wax. The pubic bones arced together in the front; in back, the sacrum—the fused assemblage of the last five vertebrae—angled between the hip bones. “Notice the shape of the sacrum,” I said. “As you get down to the end of the spine, the vertebrae get smaller and smaller. So it’s shaped like a triangle, a wedge. Now, what do you use to split firewood?”
    “Um, an ax?” offered someone.
    “Well, yes, but I was thinking of a wedge. When you apply pressure to a wedge, it tends to force things apart, doesn’t it? You see where the hip bone, or the ilium, joins the sacrum here on each side? That joint is called the sacroiliac joint. When you put pressure on this wedge, the sacrum—with the weight of your entire upper body—it pushes down, and it tends to force these hip bones apart, and strain that sacroiliac joint. That’s a common cause of lower-back pain in people my age and older.”
    I looked directly at the intelligent-design proponent in the third row. “So you see,” I said, “there are all sorts of structural features in the human body that suggest slow, imperfect evolution, rather than instantaneous, intelligent design.”
    He raised his hand, his face showing a mixture of regret and defiance. “But think about the eyeball, and the brain, and the heart. Those are complicated and amazing structures. The eyeball is a marvel of optical engineering. The brain is more sophisticated and powerful than any computer on earth. The heart makes any man-made pump look flimsy and crude.” I nodded, trying to acknowledge that we shared an admiration for those organs. “Besides,” he challenged, “what’s wrong with teaching both theories? Isn’t