Described as "by far the best book of its kind" (Henry McHenry, Evolution) and "the best introduction to the problems and data of modern palaeoanthropology yet published" (R. A. Foley, Antiquity), The Human Career has proved to be an indispensable tool in teaching human origins since its publication in 1989.

The Human Career chronicles the evolution of people from the earliest primates through the emergence of fully modern humans within the past 200,000 years. Its comprehensive treatment stresses recent advances in knowledge, including, for example, ever more abundant evidence that fully modern humans originated in Africa and spread from there, replacing the Neanderthals in Europe and equally archaic people in Asia. With its coverage of both the fossil record and the archeological record over the 2.5 million years for which both are available, Klein emphasizes that human morphology and behavior evolved together. Throughout the text, Klein presents evidence for alternative points of view, but also does not hesitate to take a position.

In addition to outlining the broad pattern of human evolution, The Human Career details the kinds of data that support this pattern, including information on archeological sites, artifacts, fossils, and methods for establishing dates in geological time.