• Choose a category
• All
• Classic-Fiction

By Root 1485 0

projection behind the ear. A pneumatized mastoid is characteristic of Australopithecus robustus. The mastoid in the small Hadar individuals (Lucy), A. africanus, and Homo sapiens is nonpneumatized. The difference in mastoid structure between the large and small Hadar individuals, along with dental evidence, convinced Olson that two species rather than one were found at Hadar (Herbert 1983, pp. 10 –11). The larger individuals were, according to Olson, a population related to Australopithecus robustus, and the smaller individuals, including Lucy, were the earliest members of the Homo line. This is an interesting variation of the original two-species interpretation of the Hadar fossils, as proposed by Richard Leakey, who placed the larger individuals in the Homo line and characterized the smaller Lucy as a surviving Ramapithecus. Johanson and his supporters “took great exception to Olson’s analysis, showing that the AL 333-45 basicranium is distorted and, if anything, is Homo-like” (Groves 1989, p. 262 ).

Dental evidence has also caused some workers to question the the view that a single species was present at Hadar. In Lucy, the first premolar has a single cusp, but in the other Hadar jaws, the premolars, like those of modern humans, have a double cusp. Science News reported: “Yves Coppens, director of the Musee de l’Homme in Paris . . . and an original cosigner on the paper identifying A. afarensis as a species has now reversed himself based on the dental evidence — specifically the existence of both single-cusp and bicuspid premolars in the sample — he says there must have been two species coexisting at Hadar” (Herbert 1983, p. 11). Johanson and White, however, said that in an evolving line, some individuals would have the single cusp and others the bicuspid tooth.

Stern and Susman, like Johanson, originally believed the Hadar fossils represented the males and females of a single species exhibiting a high degree of sexual dimorphism. According to their view, the small females, including Lucy, would have been quite arboreal, the larger males less so.

Stern, however, eventually backed down from the sexual dimorphism concept. Science News reported in 1983: “he argues that the finger bones clearly sort themselves into two groups; one group [the small individuals] has strongly curved fingers — exactly like African apes — and the other [the large individuals] has less curved . . . fingers, halfway between gorillas and humans” (Herbert 1983, p. 9).

Stern said: “The finger bones pushed me over the edge. Taken in conjunction with the differences in the ankles and leg bones, I had to ask myself: Do you ever see such difference in living animals? And the answer is no — never. It’s just too big a difference to be sexual dimorphism” (Herbert 1983, p. 9). Apparently, both species would have manifested arboreal behavior. Even the large First Family specimens had finger bones curved more than those of humans. They also had, as we have seen, long curved toes and a femoral anatomy similar to that of apes.

Where does all this leave us regarding our understanding of Australopithecus afarensis? Johanson and White and their supporters say A. afarensis, a terrestrial biped, was ancestral to A. africanus and the robust australopithecines, a line that finished in extinction. They also said A. afarensis was ancestral to the line leading from Homo habilis to Homo sapiens. Others say A. afarensis was a variety of A. africanus, which gave rise to the Homo line. Still others take a two-species approach. Tardieu (1981), studying the postcranial evidence, particularly the femurs, concluded that the larger individuals at Hadar represented the Homo line and the smaller individuals, like Lucy, something else. Y. Coppens, from studies of the dental evidence, reached a similar conclusion (Weaver 1985, pp. 592, 595). Richard Leakey also took the multiple-species approach, claiming that Lucy was a surviving Ramapithecus whereas the larger Hadar specimens represented the Homo line. Olson, studying features of the cranial anatomy, concluded that the larger