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Why does the human body look and function the way it does?

The basic question I ask — why does the human body look and function the way it does— requires an evolutionary perspective because nothing in biology makes sense except in the light of evolution. An evolutionary approach to human anatomy and physiology not only helps us to understand better why humans are the way they are, but also helps provide key insights on how to prevent many kinds of illnesses and injuries.

Heads    »  Locomotion    »   Fossils, Bones, and Experiments     


pictures of heads and skullsSome of my research focuses on the unusual nature of the human head (for a summary, see my book: The Evolution of the Human Head, Harvard University Press, 2011). Unlike other mammals, we have very large brains, nearly balanced heads with short vertical necks that attach near the center of the skull’s base, no snouts, external noses, small teeth, short round tongues, a descended larynx, and tiny faces that are tucked almost beneath the frontal lobes. How, when, and why did these features evolve? What do they tell us about the selective forces that acted during human evolution? And how can we use an evolutionary approach to the head’s anatomy to prevent common problems such as malocclusions and myopia?


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The human body below the neck is also unusual in several respects related to locomotion. I am especially interested in four questions:

1. When, how and why early hominins became bipeds? In collaboration with other researchers, I study early hominins such as Sahelanthropus and Australopithecus to understand how and why these hominins became bipeds, how they walked, ran and climbed, and how the evolution of human locomotion transformed the human body. 

2. When, how and why did humans become so exceptional as long distance endurance runners? My research with Dennis Bramble and other colleagues, suggests that long distance endurance running played a key role in the evolution of the genus Homo.  We have found and continue to study novel human features, from head to toe, that help us be great endurance runners, including spring-like arches in the foot, short toes, long tendons in the legs, a large gluteus maximus, unusually large joints in the legs and spine, a nuchal ligament connecting the head and neck, low and wide shoulders that are decoupled from the head, an elaboration of sweat glands, and loss of body fur. 

3. How does the human foot work during walking and running without shoes? Humans have been walking and running for millions of years, and until recently we did so mostly barefoot or in very simple shoes such as sandals or moccasins. Our research shows that habitually barefoot or minimally shod humans tend to walk and run differently than shod people, often in a way that leads to very low collision forces, even on very hard surfaces. We are currently studying how barefoot styles of walking running may prevent common deformities and injuries.

4. How do bipedal humans maintain stability when standing, walking and running?  Since being bipedal is inherently less stable than being quadrupedal, hominins have had to evolve all sorts of mechanisms to save energy when standing (especially pregnant females), and to save energy and maintain stability of the center of gravity and the head when walking and even more so during running.

Fossils, Bones, and Experiments

pictures of heads and skullsMy lab employs a host of experimental and comparative methods to examine how key human features grow and develop, how they function, how their function affects performance, and how and when they evolved. Major methods used in my lab include:

  1. morphological analyses of the fossil record
  2. comparative morphological analyses of other primates and mammals
  3. analyses of skeletal growth and development (at cellular, histological and macro levels)
  4. experimental biomechanics of the musculoskeletal system (kinematics, kinetics, strain, EMG, VO2 etc)