Designer Feet: Foundations for Walking, but Not up the Evolutionary Ladder

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God designed the feet of humans and apes differently, each to suit the way they walk.

Among living primates, only humans walk efficiently and easily on two legs. And many evolutionists believe bipedal locomotion was the springboard for our braininess. Are our feet the foundational distinction between knuckle-walking apes and us? How did we learn to walk this way? Enquiring evolutionists want to know!

When trying to parse out just how humans evolved a walk unlike that of our supposed chimpanzee cousins, evolutionary scientists like to compare our feet and ankles. They are similar, each with 26 bones, but they bend and flex in different ways while walking. A new study comparing the feet of humans and chimps during bipedal locomotion has revealed surprising facts about the way our feet move. Some of these paradoxical and hitherto unappreciated features do not fit easily into conventional evolutionary ideas about our walk up the evolutionary ladder.

Foot Form and Function: To Arch or Not to Arch

Certain features of the human foot contribute to the efficiency and balance of our upright gait. For instance, with each step, after a bone-loosening heel strike allows the foot to adjust to the surface underneath, the foot’s bones momentarily lock together, forming a rigid lever to heave us forward. Arches also make bipedal locomotion natural for us. Our longitudinal arch, running front to back, has a higher part on the inside of the foot (the medial longitudinal arch) and a lower part on the outside of the foot (the lateral longitudinal arch). The human foot also has another arch (the transverse arch) spanning from side to side, roughly perpendicular to the longitudinal arches.

Our arches act like springy shock absorbers. As we walk, our arches also transfer our weight around the foot’s outer edge to the ball of the foot. With the ball as a fulcrum, we then push off, catching ourselves with the other foot. As our arches stretch downward and snap back, they gather and release energy into each step. Furthermore, as we will discuss below, new research has uncovered an additional uniquely human source of springy power that, at the last moment, energizes each step’s push forward. Is it any wonder that Leonardo da Vinci reputedly called the human foot “a masterpiece of engineering and a work of art”?1

Arched feet are a signature feature of humans, even so-called flat-footed ones. And it isn’t just the bones that form our arches but the soft tissues that tug on them, securing them in just the right dimensions, allowing and restricting their motion so that they function properly.2 Arched feet are, by the way, the basis for the evolutionary interpretation of the famous Laetoli footprints, for they appear to have been made by human feet at a time evolutionists believe humans did not yet exist.

Chimpanzees do not have arched feet. Chimp feet do not form a rigid lever. And they bend and flatten dramatically in ways most normal human feet do not. With its opposable thumb-like toes, the chimp’s very mobile foot is better suited for grasping tree limbs or walking on all fours than strolling down Main Street.

The Pathway to Walking: Two Roads Diverging Over Evolutionary Time

Evolutionists believe humans and chimpanzees share a common ancestor from which each of our lineages diverged millions of years ago. Their side of the supposed split continued to swing in the trees and knuckle-walk through the fields. Our side of the “family” evolved to walk all over the world, think great thoughts, and fly to the moon. Walking upright is considered a crucial step in the evolution of our bigger, better brains.

The human foot . . . differs from the chimpanzee foot in even more ways than previously thought.

To compare the chimp and human foot in hopes of learning more about the evolution of walking, Nathan Thompson and colleagues have been watching subjects walk at Stony Brook University. Really watching! They’ve been using sophisticated technology to compare chimp and human feet and ankles at multiple points from multiple angles. Until now, much of what was known about chimp and human feet has come from less technological methodology. The human foot, they have learned, differs from the chimpanzee foot in even more ways than previously thought. And those differences are so paradoxical that the evolutionary story of their kinship through a common ancestor has become even more twisted and untraceable.

Though bipedal locomotion is not particularly efficient for chimps, they can do it and obligingly did so for this study. That way, the behavior of the chimp’s foot bones and joints could be compared directly to those of humans performing the same function. The researchers used motion capture imaging to analyze the feet of five men and two male chimpanzees while they walked. It turns out that the human foot’s bones shift a lot more during walking than anyone previously realized. In fact, despite the human foot’s ability to morph itself into a rigid lever during each step, a multidimensional perspective revealed a surprise. By viewing the foot from different angles and comparing it to chimp feet, researchers discovered that parts of a human’s walking foot are even more mobile than a chimpanzee’s! This information will force evolutionists to adjust the way they tell their story of bipedality.

Nicholas Holowka of Harvard's Department of Human Evolutionary Biology, lead author of the study published in the Journal of Human Evolution, explains,

This finding upended our assumptions about how the feet of both humans and chimpanzees work. Based on simple visual observation, we've long known that human feet are stiffer than those of chimpanzees and other apes when the heel is first lifted off the ground in a walking step. What surprised us was that the human midfoot region flexes dramatically at the end of a step as the foot's arch springs back into place following its compression during weight-bearing. This flexion motion is greater than the entire range of motion in the chimpanzee midfoot joints during a walking step, leading us to conclude that high midfoot joint mobility is actually advantageous for human walking. We never would have discovered this without being able to study chimpanzees with advanced motion capture technology.3

Our Incredibly Flexible Feet

By zooming in more precisely on the differences between the chimpanzee and the human foot during bipedal walking, Holowka’s team hoped to learn more about the evolution of the human foot and bipedal locomotion. In the process, they learned more about the complex ways in which the human foot moves. Our foot’s marvelous design, it turns out, is even more marvelous than we knew.

The discovery that the mid-section of many people’s feet has more chimp-like mobility than had been considered normal is not new. For instance, passive manipulation of the foot and ankle bones in cadaveric human and chimpanzee feet has shown that they have a similar range of motion. The feet of the living have likewise already shown that the human foot has more mobility than some thought it should. For instance, in 2013, Jeremy DiSilva and Simone Gill measured the downward pressure exerted by different parts of the foot in barefoot adults visiting the Boston Museum. Eight percent of them had an exaggerated flattening of the foot as it rolled forward.4

A similar downward bend normally forms in a chimp’s midfoot as it walks. This bend is called a midtarsal break. DeSilva and Gill interpreted their observation as a reflection of our common ancestry with apes, a feature our forebears had left in the trees. As we discussed in “Flexi-feet: Did Some Humans Fail to Leave Them in the Trees?” They suggested the midtarsal break decreases bipedal walking efficiency and had therefore evolved away in most people. Others disagreed, suggesting that such midfoot flexion would make the foot more stable in the event of a sudden change of speed. Clearly more research was needed.

This video shows the complex dynamic shifts in the position of the human foot and ankle bones during bipedal walking.

Holowka’s Stony Brook study has added greatly to the understanding of our surprisingly flexible foot. While acting as a rigid lever to help propel our body weight up and forward, the foot and ankle bones are temporarily locked in an arrangement that is quite stable. Yet at the same time, researchers have found, muscle movements cause these same bones to move relative to each other, preparing the foot to suddenly flex as we push off from the ground. The sudden midfoot flexion adds power to our push. And the push-off movements are all coordinated with the ankle bones’ movements, adjustments that not only optimize the foot’s leverage but also work with the leg and hip to optimize power and balance.

From a biophysical engineering point of view, our foot is a masterpiece. While preparing to push off, the foot and ankle bones turn in such a way that the ball of the foot becomes the fulcrum over which the ankle propels us forward. Because the fulcrum for this anatomical lever is as far as possible from the ankle’s axis of rotation, this is the best possible arrangement for gaining a powerful step. And because the human foot remains rigid and then dramatically flexes—pushing the ball of the foot and the big toe to the ground as the calf muscles contract—humans achieve a powerful push forward, a push chimpanzee feet cannot produce.

Chimpanzees were not designed to walk habitually on two legs. Therefore, their feet were not designed to make it easy. No surprise, really. The ape’s foot is not engineered to facilitate bipedal locomotion, and ours was.

Despite the resemblance of the human’s sudden foot bend to a chimpanzee’s midtarsal break, researchers found that the sudden flexion that occurs as a human foot pushes forward does not occur at the same time as the chimp’s midtarsal break. And timing here is everything. While there is a lot more motion going on in both chimp and human feet than previously thought, the moments when their bones move do not match up. Finally, the human big toe, far less mobile than an ape’s, provides a robust push-off from which the long lever of the foot and its attached calf muscles push off with power unmatched in the chimpanzee’s step.5

Foot Arches

Even more amazing than manmade arches, which bear the weight of stationary buildings, our feet are designed with three different arches that bear the shifting weight of moving bodies. Image from Answers magazine.

Implications of Our Incredibly Springy Step

Evolutionary scientists are already convinced that ape-like ancestors evolved into humans over millions of years. They are trying to find the footprints for that transition in the fossils of extinct varieties of apes and humans as well as in the anatomy of living humans and apes. They will merely view the Stony Brook study as evidence that the evolution of bipedality was more complex than previously thought. When stripped of evolutionary presuppositions, however, what the study affirms is that each foot—human and ape—is designed with enormous complexity, superficial similarities, and vital distinctions equipping its owner to move in the way God designed.

Can paleontologists tell from fossilized feet how a primate walked? Well, the study’s authors reviewed the fossils of various hominid6 feet to see if the interpretation commonly applied to the fossil record is reliable. What they found is that the feet of a Homo habilis fossil and two Homo erectus fossils clearly had a human type of longitudinal arch, a human big toe, and other features associated with the modern human’s way of walking. The fossil feet of various australopithecines, however, while possessing a few specific joints resembling those in humans, lack the definitive features it would take to be bipedal.7 This is, of course, not a surprise to creationists. After all, humans—but not apes—were designed by God with all they needed to walk upright. Because God also designed both humans and animals to reproduce and vary only within their created kinds, all varieties of humans throughout our 6,000-year history would have still exhibited the ability to stand up and walk on their own two feet.

The evolutionist authors of the study have highlighted a number of distinctions between the human and the chimpanzee foot.

Thus, the evolutionist authors of the study have highlighted a number of distinctions between the human and the chimpanzee foot. They, like others, have also shown that the bony anatomy of the foot and ankle does not reveal whether their owners walked upright or not. This calls into question the claims of those who see ancestral bipedality in the bones of various extinct apes. Their discovery does nothing to reveal common ancestry between chimps and humans. Neither does it map some sort of evolutionary pathway to bipedality. Those who think it does are basing their conclusions on preconceived beliefs that apes and humans do share a common ancestor and that walking bipedally was something that had to evolve and helped us become human.

On the contrary, the uniqueness of the human foot highlights the wisdom of our Creator God. Its dynamic design allows it to change characteristics at each moment of every step. But the anatomical manifestations of His wisdom do not stop there. The foot is not an isolated structure. An alternating connection to the ground beneath as we move, each foot’s movements are coordinated with movements in the ankle, leg, knee, thigh, hip, and back. These great designs all work together, enabling us to walk upright.8 The Creator God of the Bible knew just what it would take anatomically to equip His creatures—be they the humans made in His image or the apes and other animals—to walk in the ways He intended.

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Footnotes

  1. This statement is widely quoted and commonly attributed to Leonardo da Vinci, whose sketches of the human foot confirm his familiarity with its design.
  2. For example, the transverse arch, which is formed by the bases of the metatarsal bones and the four adjacent ankle bones (the cuboid and the three cuneiforms), is supported by ligaments, fascia, and the fibularis longus muscle. This muscle originates laterally just below the knee, and its long tendon curls around the ankle, passes through a groove designed for it on the cuboid bone, and spans across the arch under the foot. Similarly, the longitudinal arches are formed by the arrangement and shape of the metatarsals and the heel and ankle bones. The longitudinal arches are held in place and supported, however, by several ligaments, tendons, muscles between the foot and ankle bones, and muscles that originate in the leg.
  3. New York Institute of Technology, “Chimpanzee Feet Allow Scientists a New Grasp on Human Foot Evolution,” ScienceDaily, February 8, 2017, https://www.sciencedaily.com/releases/2017/02/170208131906.htm.
  4. This higher-than-expected midfoot flexibility was associated with people who tend to hyperpronate their feet as they walk, which includes the more flat-footed among us. DeSilva and colleagues have published additional work exploring the significance of a midtarsal break in humans.
  5. Nicholas B. Holowka, Matthew C. O'Neill, Nathan E. Thompson, and Brigitte Demes, “Chimpanzee and Human Midfoot Motion During Bipedal Walking and the Evolution of the Longitudinal Arch of the Foot” (Journal of Human Evolution 104 [2017]: 23–31, doi:10.1016/j.jhevol.2016.12.002), 28.
  6. The terms hominid and hominin are both words whose definitions embody the evolutionary assumptions (1) that humans evolved from an ape-like ancestor through a series of pre-human and extinct human species and (2) that humans and modern Great Apes (chimpanzees, gorillas, and orangutans) share a common ancestor. Hominid (as it is currently used by most writers) refers to all these individuals—modern humans, modern Great Apes, and all presumed ancestors of both, back to the common ape-like ancestor. Hominin refers only to the human side of the evolutionary lineage after it branched off from the common ancestor supposedly shared with apes. Hominins are thus modern and extinct humans and all their immediate ancestors, back to the common ape-like ancestor.
  7. Holowka, O’Neill, Thompson, and Demes, “Chimpanzee and Human Midfoot Motion During Bipedal Walking and the Evolution of the Longitudinal Arch of the Foot,” 29.
  8. Those foot bones that loosen as the heel strikes the ground do so as the lower leg and hip rotate inward, prompting the joint between the uppermost ankle bone and the heel bone (the subtalar joint) to evert slightly. This loosens the foot and ankle bones, allowing them to adjust to uneven surfaces and absorb impact while they slide into the optimal positions to bear our weight. Then, balanced by our curved lower back and guided by the orientation of the gluteus medius muscle in our uniquely human hip anatomy, the entire lower limb reverses the direction of its rotation as the foot rocks forward, causing that subtalar joint to now rotate inwardly. This begins locking the bones of the foot into their more rigid arrangement. The ligaments, tendons, and tough plantar fascia that support the foot’s arch all contribute to this developing longitudinal rigidity, maintaining the arch’s stability and the springiness as the foot propels the body forward. And now, thanks to the Stony Brook chimp-human-walking foot study, we know that the bones in the human midfoot retain a lot of mobility even while they are locked together, mobility that increases the power of our every step.

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