Despite more recent debate regarding the discovery of the Lomekwi 3 stone tools, which were mostly produced by a block-on-block method involving less fine manipulation, that were dated to 3.3 million years ago, it is largely recognized that the intentionally modified stone tools started to appear at approximately 2.6 million years ago. Some scholars argued that early hominins had used possibly modified tools before that time and that those tools were not preserved for different reasons. Past research has alluded to the correlation between continuous heavy use of muscles and the possible presence of entheseal changes on bones. The purpose of this study is to identify the entheses related to heavy habitual use of forearms and hands. Individuals from both the Robert J. Terry Collection and the William M Bass Collection were evaluated utilizing the protocols of previous studies of the arm and hand muscle usage during the manufacture of Oldowan tools. This study also observes entheseal developments on chimpanzee skeletons. The research contributes to what is known about entheses stimulated by heavy labors and may be a reference for future studies concerned with the tool-making capabilities among early hominins predating the Oldowan technology.