McMahon liked to integrate his hobbies and science. He enjoyed rowing his single shell on rivers and lakes. After observing that larger shells with more rowers could glide past him at high speed, he developed a simple mechanical model to explain why. McMahon's rowing project catapulted him into the world of biological scaling, a transition that led him to develop the theory of ‘elastic similarity’. The guiding principle of this theory is that organisms of different sizes are built so that their structures experience similar elastic deformations in their everyday lives. McMahon measured the dimensions of animal bones and trees to see how plausible his theory was. He spent a sabbatical in Vermont, dismantling and measuring the dimensions of an entire tree, and discovered that longer tree limbs are relatively stouter than shorter limbs. As a result, all limbs droop to a similar angle under their own weight — as predicted by the elastic similarity theory.
In 1969, McMahon met the late C. Richard Taylor, a fellow Harvard professor and comparative physiologist, who profoundly influenced McMahon's career by introducing him to the mysteries of animal locomotion. McMahon's interactions with Taylor were extraordinarily fruitful because their scientific styles differed dramatically. When faced with a difficult question about how animals work, McMahon pulled out a piece of paper and derived a mathematical model to answer the question. In contrast, Taylor designed an elegant experiment. Although McMahon and Taylor did not publish many papers together, they shaped the scientific styles of their students, many of whom learned the power of bringing together models and experimentation. McMahon's view of how mathematical modelling can be used to understand locomotion is demonstrated in his influential book Muscles, Reflexes and Locomotion (Princeton Univ. Press, 1984).
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