DATING THE FIRST PITCH: THE EVOLUTION OF THROWING IN PRIMATES

Abstract

The evolution of throwing behavior influenced many other aspects of human development. Published research associates the behavior with the development of human language, motor coordination, and highly improved hunting ability. Because most early hominin species are extinct and the fossil evidence is limited, non-human primates are currently the most useful and readily available option for research on fundamental hominin behavior. However, even in chimpanzees, the most advanced non-human thrower, the behavior is undeveloped and inaccurate. The majority of modern research compares living primate throwing tendencies to that of modern humans, but very few have analyzed throwing within the primate phylogeny. The current study expands on the already rich library of primate throwing research by analyzing anatomical changes that occurred during primate evolution that may have contributed to the evolution of throwing. Preliminary data collection was based on e-mails to primate sanctuaries and published literature to identify which species throw and how they do so. Non-human primates were placed into one of three groups based on their throwing tendencies and posture: Thrower, Tosser, or Non-Thrower. Resources provided by the Smithsonian Institute were used to make measurements of two anatomical structures, the scapula and relative arm length, ulna to humerus, which literature indicates are indicative of throwing. Results revealed a significant difference in both anatomical features between Throwers and Non-Throwers. Tossers possess scapula similar to Throwers and relative arm lengths similar to Non-Throwers, which exposes a potential evolutionary relationship between quadrupedalism, throwing, and scapular anatomy. Results confirmed Calvin et al.’s original hypothesis that human throwing originated in underhand tosses, and adds additional detail regarding the anatomy and identity of the first throwers. The first pitch was thrown underhand by a quadrupedal primate. As evolution brought about new anatomical features to cope with a challenging environment, a “true” throwing ability evolved to allow for a more precise delivery. Future analysis should focus on the anatomical differences between the different quadrupedal primates to identify which features allowed underhand tosses to develop into overhand throws.