Naming Lucy: Taxonomic reasoning in paleoanthropology

The 3.2-million-year-old female hominin skeleton retrieved in Ethiopia’s Afar region in November 1974 underwrites a paradigmatic history of naming. First known through the locality number assigned to the site of the discovery, AL-288-1, she soon became the human ancestor par excellence and an ambassador of human evolutionary studies with the nickname “Lucy” (also known as Dink’inesh in Amharic). The Linnean naming of the species, Australopithecus afarensis, formalized through the 1978 publication in Kirtlandia after a wave of fossil discoveries at Hadar and Laetoli, channeled debates on the evidence and methods of classification in paleoanthropology.

In this talk I will show how Lucy’s systematics offers an emblematic window into the evidential basis and constraints of taxonomic reasoning in early hominin paleoanthropology, as well as what drives the revision of taxonomic attributions. By looking at changing interpretations of the Hadar and Laetoli fossils, I will highlight how taxonomic judgments are never made in a vacuum but interact with the background knowledge available at each time, sometimes countering prevailing schemes of hominin evolution. Further, I will focus on the inferential strategies that have been employed to justify single species attribution of the Hadar and Laetoli specimens and that represent today a typical logic of interpretation of past morphological variation. These include various forms of comparative thinking applied in analyses of ranges of variation between the fossil material and extant living ape taxa and between the fossil material and other extinct species, and chronological thinking evident in the appreciation of the temporal dimension of variation. Finally, I will draw on Lucy’s example to discuss what taxonomic hypotheses are hypotheses of and the relationship between evidence and conceptualizations of “species” in paleoanthropology.