The discovery and initial interpretation of ‘Lucy’ as a tipping-point in paleoanthropology

In retrospect, it is possible to see the middle-1970s discovery and initial analysis of the fossil NME AL 288-1, affectionately known as “Lucy,” as a major symbol, and even the driver, of a significant reorientation in the science of paleoanthropology. That change of perspective affected both the conceptualization and the practice of the science of human evolution. Before Lucy was discovered, the interpretation of the human fossil record had been dominated by practitioners of traditional expert pronouncement or by followers of the newer linear gradualism preached by Ernst Mayr. Either way, paleoanthropologists had earlier seen fossil hominin species as mere heuristic conveniences, rather than as real, bounded, entities that had played critical—and in principle identifiable—roles in the human evolutionary drama. But with the addition to the hominin roster of the new species Australopithecus afarensis, exemplified if not typified by “Lucy,” it began to be obvious that, in stark contrast to accepted practice, hominin fossil species needed not only to be properly defined, but also to be situated within specifically articulated hypotheses of relationship. Nowhere was the clash between the old and the new perspectives more dramatically displayed than in the famous 1981 “debate” between Richard Leakey and Donald Johanson, moderated by the venerated Walter Cronkite. When challenged by Johanson to provide an alternative to his phylogenetic framework for A. afarensis, Leakey, a classic practitioner of authoritarian pronouncement, brusquely declined to do so and abruptly terminated discussion. There could have been no better way than this abandonment of dialogue to dramatize the deficiencies of traditional paleoanthropological practice; and it is possible to argue that this nationally televised event marked an important stage in the transition to the current era, in which paleoanthropologists, while often regrettably clinging to an ultimately Mayrian taxonomic minimalism, nonetheless at some level acknowledge not only the diversity implicit in the morphological heterogeneity of the hominin fossil record, but also the importance of organizing that diversity via explicit and testable phylogenies.