In his 1982 book Man, the Tottering Biped the South African-born anatomist and paleoanthropologist, Philip V Tobias (1925 – 2012), questioned the conventional wisdom, developed from Charles Darwin onwards, that standing in an upright stance on two feet freed our arms for tool making and tool using and marked a significant advance in human evolutionary history.
Tobias argued, instead, that the capacity to sit upright occurred long before the ability to stand on two feet and walk bipedally. It was sitting, in his view, that allowed our ancestors to develop a range of manual skills and with them the growth of a large brain.
But Tobias made a further point about Homo sapiens’ achievement in standing upright:
“The way in which the body adjusted its structure and its bio-mechanics to the new way of uprightness and bipedalism may be described as little short of ingenious. Nonetheless, after perhaps four million years or more, we have not yet evolved a fault-free mechanism. Our bodies are still subject to what Sir Arthur Keith called the ills of uprightness. They include flat feet, slipped discs, hernias, prolapses and malposture. These maladies of uprightness account for much that keeps today’s orthopaedic surgeons busy. So the mechanism of man’s posture and gait, though resourceful and craftily contrived, is imperfect. The first human ancestors to come upright became heir to a host of new problems.”
That’s an impressive list but even so, it leaves out: plantar fasciitis, Achilles tendinitis, ankle sprains, shin splints, fallen pelvic floors, hernias, sway back (lordosis), a sideways curvature of the spine (scoliosis), a rounded upper back or hunch back (kyphosis), and spontaneously fractured vertebrae.
No one would disagree that standing upright, the head poised on top of the spine, is a truly remarkable achievement. Many biological anthropologists, such as Craig Stanford of the University of Southern California, believe it is the key defining feature of Homo sapiens. As he says in his 2003 book Upright:
“Of the more than two hundred species of primates on earth today, one is bipedal. Of more than 4000 species of mammals, one – the same one – is fully bipedal when walking (a few oddities such as kangaroo rats and meerkats stand bipedally for a few moments at a time). If we include thousands more kinds of animals – such as amphibians and reptiles – walking on two feet emerges as the most unlikely way to get around. Kangaroos and birds such as ostriches and penguins are bipedal – sort of. But they are built on an entirely different body plan, and are not, strictly speaking, relying only on their legs for transport.”
Only the human primate, then, is able to come to a truly upright stance with fully extended knees and hips – that is, without the bent leg joints found amongst bonobos and chimpanzees, our nearest relatives – and has the capacity to remain in that attitude for a significant amount of time.
Nevertheless, Tobias’s perspective on the problems of uprightness has plenty of contemporary supporters. “The human vertebral column is unique in its sinusoidal curvatures that allow the upper body to balance over the hips,” anatomist and physical anthropologist Bruce Latimer of Case Western Reserve University recently argued at a meeting of the American Association for the Advancement of Science (AAAS). “Turning a spine originally adapted for a quadruped into one that is perpendicular to the ground has resulted in numerous problems that are unique to our species. If you take care of it, your spine will get you through to about 40 or 50. After that you are on your own.”
At the AAAS meeting Latimer was backed by Boston University’s Jeremy DeSilva, a functional morphologist and an expert on the evolution of the foot and ankle joint. DeSilva notes that humans are peculiarly susceptible to a wide variety of injuries in the lower limbs. Appealing to evidence from fossil records he says, “We have long suffered foot problems, demonstrating that many modern foot ailments are not solely the result of our more recent sedentary lifestyle.”
On the other hand, some anatomists and paleoanthropologists do not accept the assumption that selective pressures are responsible for the many problems that contemporary humans often develop. “If that were true, natural selection would have its toll and we’d be extinct,” argues evolutionary biologist Daniel E Lieberman of Harvard University. “What is more likely is that many people sit in chairs all day, get no exercise, and thus have weak backs. We did not evolve to sit in chairs all day.”
Lieberman is, of course, famous for promoting the benefits of barefoot running. In 2004, he co-authored a paper with the University of Utah’s Dennis Bramble, ‘Endurance Running and the Evolution of Homo’, published in Nature in which the theory was advanced that running without shoes was preferable to shod feet because it promoted a forefoot or mid-foot contact with the ground, rather than an injury-inducing heel strike caused by the elevated heel of the modern running shoe.
So there is a split between the theories. How to adjudicate between the competing claims? Differences among social groups and individuals within those groups in terms of general coordination must be part of the explanation. Indeed, it’s interesting to consider that Tobias’s immediate predecessor as director of the School of Anatomy at the University of Witwatersrand, Australian-born Raymond Dart (1893 – 1988), took a very different line about the evolution and significance of uprightness. In a 1961 paper, ‘Weightlessness’, he anticipates Lieberman’s “we weren’t built to sit all day” argument:
“Our muscular mechanisms were elaborated by nature over a thousand million years not to be the types of static painful machines into which society and its machines have so far transformed the vast majority of them. They were built up against the forces of gravity specifically to make us capable of such perfection in balancing as to float as it were in space over the surface of the Earth, joyfully, painlessly.”
That perspective is underpinned by researchers at the University of York, who in a recently published paper in Antiquity, reject the traditional theory that climate change forced our early forebears out of the trees and onto two feet. Instead, according to lead researcher paleoanthropologist Isabelle Winder the key to the development of bipedalism were the adaptations required to negotiate the rugged landscape of east Africa shaped by volcanoes and shifting tectonic plates during the Pliocene era: “‘Scrambler man’ pursued his prey up hill and down dale and in so doing became that agile, sprinting, enduring, grasping, jumping two-legged athlete that we know today.”
The practical lesson for those of us who sit around most of our waking time? Get up on your own two feet and take a walk. Alternatively, run up and down that hill.
A version of this article has appeared at anthropologyworks.com
Dr Sean Carey is research fellow in the School of Social Sciences, University of Roehampton
* Published in print edition on 28 June 2013