An enthesis is the interface where tendon meets bone, providing both muscle anchorage and stress dissipation. Previous anthropological research suggests size and complexity of entheses observable in osteological material, are indicative of the strain magnitude resulting from repetitive muscle contractions during the performance of daily routines. These proposed “musculoskeletal stress markers” are routinely incorporated into bioarcheological studies as evidence of general activity patterns past human populations participated in. However, much of how this complex osteotendinous interface develops and responds to mechanical strains is poorly understood. The following review seeks to shed light on this structural enigma by synthesizing current findings in both the clinical and anthropological literature, in the interest of generating new conversations in how entheses respond to contractual forces and the systemic influences (i.e., genetics, hormones), that surround their morphological development. Only once we truly understand the etiology of tendon insertion sites, will the value of enthesial research in reconstructing human behavior be determined. Anat Rec, 2012. © 2012 Wiley Periodicals, Inc.