Human Physiology and Acheulean Handaxe Design
Acheulean handaxes have played a leading role in our understanding of the cognitive and behavioural abilities of early hominins. An enormous amount of scholarly attention has been dedicated to better understanding the role these tools played in human evolution. Since the 1960’s, experimental archaeology and increasingly sophisticated quantitative analyses have brought us much closer to answering many fundamental questions about their true nature. Nonetheless, uncertainty remains about morphological differences, symmetry, and the meaning behind Acheulean handaxes’ remarkable longevity and spatial distribution. This dissertation presents the results of a series of experiments designed to study handaxe design and sources of shape variation using novel methodological approaches. The main goal is to examine their shape variation from a physiological perspective since most studies focus on functional and/or cultural aspects of handaxe manufacture and use. This is accomplished in two ways, one by looking at limitations in humans’ visual perception, and the second by examining how mass is distributed in Acheulean handaxes. The first goal examines limitations in humans’ visual perceptive abilities for distinguishing size differences between three-dimensional (3D) objects by using a series of different sized 3D printed models which were presented to participants who were asked to iii differentiate the size differences. The results indicate that our ability to distinguish size differences drops significantly below 3%. As such, it is suggested that this physiological limitation would introduce shape variation in handaxe assemblages. The second goal examines the role that balance played in handaxe design and manufacturing since neuroscience studies indicate that humans manipulate handheld tools according to their center of mass (CM) location and well-balanced tools reduce stresses and injuries in the hands, arms, and shoulders. Therefore, a novel methodology was developed that turns the CM location into a ratio that can be compared between handaxes. The results indicate that the CM location was tightly controlled and is less variable than any other shape trait and is relatively independent from symmetry. Furthermore, 3D geometric morphometrics and K-means clustering analysis was conducted on South African and British handaxe handaxes in order to examine shape variation at the assemblage level.
Acheulean handaxe, Balance, Geometric morphometrics, Physiology, Symmetry, Weber fractions
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