Ask A Scientist
Why do our feet have so many bones?
Asked by: Gianna Ricci
School: St. John the Evangelist School
Teacher: Anu Rai
Hobbies/Interests: Sewing, crocheting, knitting
Career Interest: Fashion designer, talk show host
Answer from Michael Little
Distinguished Professor of Anthropology
Research area: Human adaptation to the environment Interests/hobbies: Swimming, choral singing, antique toys, books
Human feet each have 26 bones, along with many muscles and joints. This seems like a lot, but we can do a lot of things with all of these bones. We can stand upright, walk and run with these complex feet of ours, and we can even kick, dance, jump and swim!
Our hands each have only one more bone than our feet do (27 bones in total), but our hands can carry out many more tasks than our feet, such as grasping objects, writing, drawing, using tools and playing the piano. Since the hand can do numerous things while the foot is limited, the hand is called a generalized limb and the foot is called a specialized limb.
The bones in the foot include 14 phalanges (toes), 5 metatarsals, and 7 tarsals. Both of our hands and our feet are known as pentadactyl, meaning that each has five fingers or toes. Not all mammals have a pentadactyl hands or feet like humans do. Elephants and camels walk on flat pads, horses and goats walk on hooves, and whales and porpoises have fins.
Our five-toed pentadactyl feet and hands are derived from our earliest fish ancestors, who had fish fins with five sets of bones. These evolved to become the kinds of hands and feet that our primate (monkeys and apes) ancestors have. So we have a sequence of evolutionary events, from fish fins with five sets of bones to amphibians and reptiles who continued with the same pattern of bones, to mammals and then primates—all with this pattern of five sets of bones.
Finally, when primates appeared about 60 million years ago, they lived in trees and had similar hands and feet so that they could grasp tree limbs. But when apes and then humans spent time on the ground and began to walk on their feet, their feet began to evolve and change to provide better support for standing and walking rather than grasping.
One of the ways in which our foot bones are complex is in the pattern of arches that allow us to have a springy walk and to stand with less pressure on our feet. We have three arches along the length and the width of the foot. In fact, several of the tarsal bones act as keystones to support the arches (just like keystones that support a stone bridge). So, our feet are more complex than most of us imagine, and all 26 bones are needed.