Yohannes Haile-Selassie is an expert on the paleobiology and paleoecology of early human ancestors based on the fossil record.He has made fossil discoveries that are significant in human origins research and leads an international multidisciplinary team that conducts fieldwork in the Afar Region of Ethiopia. He has been instrumental in the discoveries of the principal reference fossil for Australopithecus garhi and Ardipithecus kadabba (both discovered in 1997), and he has also found fossil specimens of Ardipithecus ramidus, Australopithecus afarensis, and species of Homo including Homo erectus, as well as Homo sapiens.

Haile-Selassie is the Virginia M. Ullman Professor of Natural History and the Environment and Director of the Institute of Human Origins. He is the lead investigator for the Woranso-Mille field site, only 30 miles from the Hadar site where the Lucy fossil was discovered.