Abstract

Units as they exist today are highly abstract. Meters, miles, and other modern measures have no obvious basis in concrete phenomena and can apply to anything, anywhere. We show here, however, that units have not always been this way. Focusing on length, we first analyze the origins of length units in the Oxford English Dictionary; next, we review ethnographic observations about length measurement in 111 cultures. Our survey shows that length units have overwhelmingly come from concrete sources—body parts, artifacts, and other tangible phenomena—and are often tied to particular contexts. We next propose a reconstruction of how abstract units might have emerged gradually over cultural time through processes of comparison. Evidence from how children understand length and measurement provides support for this account. The case of units offers a powerful illustration of how some of our most important, pervasive abstractions can arise from decidedly concrete, often embodied origins.