I have been frequently asked if the huarache (Spaniah for sandal) worn by the Tarahumara, of Copper Canyon, Chihuahua, Mexico, helps them in their distance running performance. This question indicates a deficiency in knowledge about of the history of footwear use in the Americas, and plantar sensory control of mobility.
H. Sapiens have existed for perhaps 300,000 years. Foot coverings began being used by a small group of ,humans in the early Holocene (perhaps 10,000 years ago) for survival in the extreme North. They also began being used by a small group of humans with early civilizations, commencing 5,000 years ago as a symbol of status and an expression of the more ancient tradition of body art through foot decoration. Footwear use became more extensive only with the European Renaissance, when footwear were used by all social classes for the first time in human history. This practice spread beyond Europe through colonization and cultural imperialism. Foot coverings can by functional in terms of aiding survival in particular environments, such as preventing foot damage from hypothermia in the North, but excluding their specific advantage in unique environments, never functional in terms of safe and efficient mobility compared to the barefoot condition. Humans must be considered poorly adapted to footwear because they began using foot coverings so recently in evolutionary terms, there was insufficient time to adapt to them through natural selection. The adaptation for safe mobility with footwear would require extensive biological changes because balance, impact control and locomotory mechanics in humans is largely determined by sensory feedback from mechano-receptors of the plantar skin which were optimized for the condition of the bare foot in direct contact with the support surface.
Humans began populating the Americas in the early Holocene (the end of the last ice age - 10,000-15,000 years ago) through migration from the North across a “bridge” which linked Asia to the Americas. These hunter-gatherers may initially have survived on fish and sea mammals, but soon ventured east and south from the coast following a reliable protein and fat rich foot source humans require - migratory animals herds. The extreme cold of Northern Asia and the Americas made foot coverings that insulated feet essential to their existence. No footwear from this period remains, however it is thought it was initially composed of hides forming sacks that that eventually became optimized in terms of mobility to resemble the modern mukluk (kamak). These consist of the same skins but stitched with sinews which each social grouping having a unique stitching pattern that probably was used to identify the tribe. As humans migrated to more temperate zones, this mid-calf heigh robust footwear was required for thermal protection only seasonally. It was retained for winter, but under warmer conditions they undoubtedly reverted to
barefoot locomotion which allowed safer and more efficient mobility. The moccasin probably originated as an abbreviated mukluk that retained the sole stitching pattern of the mukluk for tribal identification. Despite popular notions of the native people of the Americas, the moccasin was mainly decorative rather than functional, and its use came with a health and mobility cost. Unlike the muklukIf it never was required for survival.
Large numbers of native Americans found their way to the grasslands of central North America and the woodlands of the East probably because both were were rich in grazing animals - their protein source. Wars between native tribes and with humans, however, forced some natives to less favorable locations in terms of agriculture and availability of wild animals, but offered the protection needed for survival from their enemies. This explains how the Tarahumara now occupy Copper Canyon.
Contemporary Tarahumera run barefoot or in their sandal which obviously was a recent development considering it is made of used automobile tires. Accordingly, I assume that the use of footwear by the Tarahumara was mainly due to social norms at a cost to both health and mobility - the same reason footwear are presently used by most humans in the world. Universal footwear use appeared for the first time in humans history in Renaissance Europe and this norm was imposed on native populations in the Americas through colonization and cultural imperialism.
How does the haurache worn by the Tarahumara compare to other shoes? It possesses a relatively thin and rigid interface of uniform thickness, and an effective fixation system. Consistent with the fixation system, this shoe does not permit plantar sensory information emanating from localized vertical and horizontal plantar deformations therefore impairs balance, impact control and alters the gait pattern humans have adapted to through natural selection.