Biomedical Engineering Reference
In-Depth Information
the great chain of being—with qualifications that I shall mention in a
moment. The single species hypothesis popular in the 1950s and 1960s
championed a linear, nonbranching evolutionary sequence according
to which
Australopithecus
begat
erectus
,
erectus
begat Neanderthal,
Neanderthal begat
sapiens
, and so forth. The newer family trees, by con-
trast, are often bushy, with many false starts and dead ends (extinctions),
and often more than one species living concurrently.
What accounts for the rise of the single species hypothesis and the
reluctance to appreciate fossil hominid diversity? Gould and others have
stressed the perennial bias of uniformitarianism, with its
scala natura
progressivism and preference for linear “chains” over diversifying
“bushes,” but changing local sensitivities also have to be taken into
account.
45
I have already mentioned Brace's odd ecological rationaliza-
tion, but there was also the fact that with the exposé of the Piltdown
hoax in the early 1950s, paleoanthropologists were suddenly faced with
a much narrower range of hominid skeletal morphology. (Piltdown was
a modern human cranium attached to an orangutan jaw.) Yet another
impulse was the growing concern over the out-of-control proliferation
of hominid taxa. “Lumper” Ernst Mayr, for example, contributed to the
hypothesis with his effort to reduce the clutter of hominid generic names.
In 1950, Mayr maintained that the proliferation of hominid generic
names made little taxonomic sense, and he proposed that the zoo of
names circulating at that time—such as
Australopithecus
,
Plesianthro-
pus
,
Paranthropus
,
Pithecanthropus
,
Sinanthropus
,
Paleoanthropus
—be
reduced to a single genus,
Homo
, defined by upright posture. Mayr also
maintained, though, following Theodosius Dobzhansky, and with race
clearly on his mind, that “never more than one species of man existed
on the earth at any given time.”
46
Mayr's pronouncement has to be read against the backdrop of chang-
ing views on race. Ever since Carolus Linnaeus, and interestingly unper-
turbed by Darwin, racial theorists had squabbled over how many races
humanity should be divided into. Darwin had noted the absurdity of such
exercises, with Jean-Joseph Virey distinguishing two races of humans,
Immanuel Kant four, Johann Friedrich Blumenbach five, Buffon six, John
Hunter seven, Louis Agassiz eight, Charles Pickering eleven, Samuel
George Morton twenty-two, Edmund Burke sixty-three, and so forth.
47
Long into the twentieth century, human phyletic trees often showed a
