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Bramble’s reference to today’s running in the evolutionary context he and Lieberman established provides an appropriate introduction to the exploration of the biomechanical differences between male and female marathon runners (Wilford, 2004): Today, endurance running is primarily a form of exercise and recreation, but its roots may be as ancient as the origin of the human genus.'

The description of anatomical differences between men and women,which is focused on anatomical features that are involved in running,begins with a gender-neutral discussion to establish a foundation for the more gender-specific information.

Rossi (2003) emphasizes the complexity of walking, a precursor torunning. He writes that half of the 650 muscles and tendons in thehuman body are involved in what most people consider to be the simpleact of walking. He suggests that, in the evolution of the human body,there were hundreds of adaptations' that had to take place,adaptations that required repositioning of everything in the body'over several million years. Rossi writes:

The arms, no longer needed for branch swinging, became shorter, thelegs longer, the pelvis wider, the shoulders narrower, the neck longerand more slender, the spine changed from C-shape to S-shape. Majorchanges were required in the hip, knee and ankle joints. Hundreds ofmuscles, tendons, ligaments and joints gradually shifted in position,size and function. And of course, the new posture and gait requiredimportant changes in the size and position of all the organs of thechest and abdomen.'

Rossi suggests that some of these changes were extremely significantfrom a biomechanical perspective. For instance, he calls attention tothe blood pumping requirement of the upright human form: Daily in eachindividual, approximately 74,000 quarts of blood must travel through100,000 miles of blood vessels from the brain to the feet and legs in acircular pattern. Rossi emphasizes the human engineering' challengethat was required to design a system that would counteract the effectsof gravity in moving blood vertically in this manner. Rossi’s commentsare particularly important in the context of the current discoursebecause they provide some insight into the current state of relevantanatomical features of today’s runners and how those features werederived.

The anatomy of humans, unlike that of other living creatures,provides for speed and endurance. The unique characteristics related torunning include (Science in Africa, 2005, citing University of Utah Public Relations, 2004):

• - Skull features. These features, which include sweating from the scalp and face, cool the blood.

• - A balanced head. This shape of head with a relatively flat face,small teeth, and short snout moves the center of the mass backwardwhich helps to counter the effects of moving upward and downward duringrunning.

• - A ligament running from the rear of the skill and neck downward tothe thoracic vertebrae. This feature serves as a shock absorber thataids the arms and shoulders in counterbalancing the head during runningactivity.