This week I'm reading Lone Survivors, a new book in which British anthropologist Christopher Stringer reports that some Homo sapiens wore shoes as early as 40,000 years ago.
This paleo-fact caught my eye because my husband, who is keenly interested in matters of fitness, has been talking to me lately about barefoot running. The idea — as it's been popularized — is that the natural, best way for us to run today is the same way humans have been running for hundreds of thousands of years: with our bare feet striking the earth.
I tend toward skepticism when health advice is based on what our ancestors did, without regard to variation in past behavior. So I'm wondering, if shoes are as old in some early-human populations as Stringer claims, is the barefoot-running phenomenon just another paleo-fad?
Stringer explains that the degree of robustness in toe bones allows experts to distinguish from the condition of skeletal material whether people wore shoes or went barefoot during their lives. Skeletons from 40,000 years ago at Tianyuan, China, and also 28,000 years ago from Sungir, Russia, clearly bear on their bones the marks of shoe-wearing.
Stringer writes that this ancient footwear "would have eased travel across difficult terrain and, if waterproof, could also have provided protection from the cold, wet, and snow."
If shoe-wearing has been practiced by at least some humans for so long, should barefoot-running advocates think twice?
I learned that the debate isn't correctly framed as being about shod versus barefoot running. Instead it's about whether our exercise and foot health really benefit from the expensive running shoes pushed on us as part of consumer culture.
"For most of human evolutionary history," Lieberman and his colleagues write, "runners were either barefoot or wore minimal footwear such as sandals or moccasins with smaller heels and little cushioning relative to modern running shoes."
No paleo-Nikes were available 40,000 years ago, of course, so any shoes from the time period Stringer writes about would fit well with the evolutionary pattern.
The think-twice-about-barefoot-running issue compels a look, though, at injuries in shod versus barefoot runners.
In their article "Foot strike patterns and collision forces in habitually barefoot versus shod runners," Lieberman and his colleagues explain the three ways our feet may collide with the ground during running: a rear-foot strike, when the heel lands first; a mid-foot-strike when the heel and the ball land together; and a forefoot strike when the ball lands before anything else.
The scientists took data on five groups of runners, from elite athletes in the United States and Kenya to children, and controlled for their subjects' footwear.
The key results were (forgive the inevitable pun) striking: More often than habitually barefoot endurance runners, habitually shod runners "mostly rear-foot strike, facilitated by the elevated and cushioned heel of the modern running shoe." Because of this difference, even on hard surfaces barefoot runners experience smaller collision impacts than shod runners.
By this measure, barefoot running has high potential to be beneficial. As the Well blog reported last year, however, "anecdotal evidence has mounted that some runners, after kicking off their shoes, have wound up hobbled by newly acquired injuries. These maladies, instead of being prevented by barefoot running, seem to have been induced by it."
In a point also emphasized by anthropologist Greg Downey, Lieberman notes that how we run barefoot in our modern environment matters a great deal. The Well blog quoted him as joking, "We did not evolve to run barefoot with bad form," a statement he clarified in an email reply to me this week: "I suspect one actually can run barefoot with bad form, but it is harder and more painful to do so. I think running barefoot is a great way to learn good form."
At the "Running Barefoot" website — which features the skeletal biology work of Lieberman and his colleagues — there's a great FAQ designed for people who may want to give barefoot running, or running with minimal shoes, a try. I like the site's disclaimer, too: "Please note that we present no data on how people should run, whether shoes cause some injuries, or whether barefoot running causes other kinds of injuries. We believe there is a strong need for controlled, prospective studies on these issues."
Barefoot runners can be, as the Well blog phrases it, "disproportionately enthusiastic and evangelical." Lieberman, who himself runs barefoot, adds into the mix the sensible voice of a scientist who's about hypothesis-testing and not paleo-fads.
You can keep up with more of what Barbara is thinking on Twitter: @bjkingape