Part of the diversity is historical. The species names were given long ago
and were given during a period that considered any small difference enough
to be the definition for a new species. Some of the motivation is a
recognition that history has saddled us with some relatively improper
biological definitions. Consider this from Boaz,
"The biggest bombshell dropped on the Old Guard, however, came from
Ernst Mayr, a German-trained ornithologist and specialist in the naming
(taxonomy) of species in nature. Using the new yardstick of variability within
populations, he stated that 'after due consideration of the many differences
between Modern man, Java man, and the South African ape-man, I did not find any
morphological characters that would necessitate separating them into several
genera.' He suggested that all the fossil human-like specimens that
anthropologists had discovered after so much laborious effort over the
preceding century be simply ascribed to one genus, our own--Homo. In other
words, the entire 'Age of Description,' from before Darwin to Cold Spring
Harbor, was a waste of time. His opinion was that the differences were not as
great as between genera of other animals. This assertion meant that the
wonderfully diverse lexicon of human paleontology, a virtual liguistic
playground for the classically educated, with melliferous names such as
Plesianthropus transvaalensis, Meganthropus palaeojavanicus, Africanthropus
njarensis, Sinanthropus pekinensis, Pithecanthropus erectus, and so on, were to
be replaced. Everything was now to be simply Homo, with three species: Homo
transvaalensis, Homo erectus, and Homo sapiens."
"Mayr's proposal went so far that even Washburn argued that at least the
South African Australopithecus be retained (instead of Homo transvaalensis)
because it showed such significantly more primitive anatomy than members of the
genus Homo. Mayr simply countered that the population is what the species
designates. How one determines a genus is arbitrary. The definition is gauged
by the relative amount of difference that one sees between the genera of other
animals and, in Mayr's opinion, hominid fossils don't show very much
difference. To anthropologists, this statement was a bit like telling a new
mother that her baby looks like every other baby. It did not go over
well."~Noel Boaz, Quarry, (New York: The Free Press, 1993), p. 10
glenn
Foundation, Fall and Flood
http://www.isource.net/~grmorton/dmd.htm