The first afarensis fossils were found in the mid 1970s. Their initial interpretation was controversial and remains so today, albeit to a lesser degree. While many anthropologists accept that the multitude of fossil specimens that have been attributed to afarensis do indeed represent a single, sexually dimorphic species, others believe that the fossils belong to two, and perhaps more, species. For a long time afarensis was assumed to have represented the founding species of the hominine clade and the ancestor of all later species.

The Ethiopian hominine fossils were first found in the mid-1970s in the Hadar region of that country, by an international team led by Donald Johanson, of the Institute of Human Origins, Berkeley, and Maurice Taieb, a French paleontologist. The many hundreds of fosils recovered included mostly cranial and dental specimens (but no complete cranium) and postcranial elements. The most spectacular of these finds was the partial skeleton named "Lucy"; in addition, remains of 13 individuals were found at a single site and were subsequently dubbed the First Family. It was clear from the start that some of the homninines were small while others were large.

Work continued in the region until the early 1980s, but was then suspended for almost a decade. Recent prospecting in Hadar by Johanson and his colleagues at IHO, and in the nearby Middle Awash region by Tim White, or the University of California at Berkeley, has yielded many more fossils specimens, including the first complete cranium, details of which were published in 1993 and 1994.

In addition to the fossils, a 30-yard-long humanlike footprint trail of three bipedal individuals was unearthed, which had been made (presumably by Laetoli hominines) some 3.6 million years ago in a newly deposited layer of volcanic ash. The trail provides one of the more haunting relics of human prehistory, recording a few moments in the lives of three individuals, one of whom stopped briefly, turned to look eastward (possibly at the still-erupting distant volcano), and then continued onward.

Johanson and White described A. afarensis as being much more primitive than other known hominies, with a strongly apelike appearance above the neck and a stronly humanlike form below the neck; as having extreme sexual dimorphism in body size (males larger than females); and as being ancestral to all later hominines.

 Reference: Johanson, DC, White, TD. A systematic assessment of early African hominids. Science 1979; 203, p. 321-330.