In L'Homme et la matière , Leroi-Gourhan proposes the concept of technical tendencies, that is, universal technical dynamics that operate independently of the ethnic groupings which are nevertheless the only forms through which these tendencies are concretised. The concretisation of the technical tendency in a particular ethnicity he calls a technical fact. In Milieu et techniques , Leroi-Gourhan develops this into a general theory of the relation between the technical and the ethnic. The human group, according to Leroi-Gourhan, behaves as though it were a living organism, assimilating its exterior milieu via "a curtain of objects", which he also calls an "interposed membrane" and an "artificial envelope", that is, technology. The milieu of the organism is divisible into the exterior milieu and the interior milieu. This division enables a clarification of the concept of technical tendency. A tendency, according to Leroi-Gourhan, is a movement, within the interior milieu, that gains progressive foothold in the exterior milieu. Leroi-Gourhan contributed to the methods of studying prehistoric technology, introducing the concept chaîne opératoire which denotes all the social acts involved in the life cycle of an artifact.
Evolution, memory, program
Crucial to Leroi-Gourhan's understanding of human evolution is the notion that the transition to bipedality freed the hands for grasping, and the face for gesturing and speaking, and thus that the development of the cortex, of technology, and of language all follow from the adoption of an upright stance. What characterises humanity in its distinction from animals is thus the fact that tools and technology are a third kind of memory, and thus a new form of anticipation, or programming. Anthropogenesis corresponds to technogenesis.
Legacy
The French philosopherJacques Derrida discusses Leroi-Gourhan in Of Grammatology, in particular the concepts of "exteriorisation", "program", and "liberation of memory." This discussion was particularly important in the formulation of Derrida's neologism, différance. Leroi-Gourhan is frequently cited in the two volume collaboration by French philosopher Gilles Deleuze and psychiatrist Félix Guattari entitled Capitalism and Schizophrenia. The hand/tool and face/vocalization couplings of Leroi-Gourhan play an important role in the development of Deleuze and Guattari's concepts of becoming and deterritorialisation. The French philosopher Bernard Stiegler gives an extensive reading of Leroi-Gourhan in .