The causes of morphological variation within Lower Palaeolithic stone tool assemblages have been subject to debate for decades. As a result of numerous explanatory hypotheses, it forms one of the most substantial areas of research within Palaeolithic archaeology. To date, however, very little research has ever been undertaken into the functional causes and consequences of Lower Palaeolithic stone tool form variation. Indeed, despite stone tools being functional objects tasked with the cutting and modification of aspects of the physical environment, previous researchers have preferentially sought to explain their morphology as a result of social, aesthetic, cultural, cognitive, reductive, and raw material influences. Here, this imbalance is addressed and the two principal technological components of the Lower Palaeolithic, ‘basic’ flakes and handaxes, are subject to a number of controlled, statistically robust, and archaeologically inferable experiments investigating relationships between variable tool-forms and functional performance characteristics. Results and subsequent discussion identify a number of important evolutionary, behavioural, and technological implications for Lower Palaeolithic hominins.