Biomedical Engineering Reference
In-Depth Information
radio-dated volcanic ash) and the first real evidence that
Homo
must
have lived contemporaneously with the Australopithecines. The reigning
assumption had been that early, ape-like hominids were fully replaced
by more human-like hominids, but here was a new and disturbing idea—
multiple co-existing hominid genera—that took some time to assimilate.
The nail in the coffin came in 1975, when Richard Leakey announced
the discovery of a
Homo erectus
skull old enough to have coexisted with
Australopithecus boisei
.
49
Could this be possible? Might two or three different kinds of ape-men
have lived at the same time? If so, how did they interact? Could they
have conversed with one another? Traded with one another? Fought with
one another? The idea of multiple coexisting human lineages seemed to
some a rather unsettling prospect—albeit fertile ground for sci-fi, as
writers for more than a century had already realized.
50
The story was made still more complex when it became clear that there
were more than two kinds of
Australopithecus
. A key discovery here
came in 1974 when Donald Johanson, a graduate student working at a
dig near Hadar, in Ethiopia, discovered a 3.2-million-year-old hominid
soon regarded as the first-found member of a new species, dubbed
Australopithecus afarensis
(southern ape of Afar), better known as
“Lucy” from the fact that the paleoanthropologists were rocking to the
Beatles song “Lucy in the Sky with Diamonds” (LSD), as they returned
to camp. The skeleton was only 40 percent complete, but clearly showed
that “humans” walked upright more than three million years ago.
It eventually became apparent that there were several different species
of these apelike humans (or humanlike apes) of Africa, including
Aus-
tralopithecus anamensis
, a fossil hominid found in 1995 by Meave
Leakey of the National Museum of Kenya and Alan Walker of Johns
Hopkins, and
Ardipithecus ramidus
, an enigmatic and fragmentary crea-
ture (a piece of a jaw and several other bits) found in 1994 by Tim White
in Ethiopia. The former is 4.2 million years old and the latter is about
4.4, which is not so long after the point when the ancestors of (what are
now) chimps and humans branched off from one another. The new mil-
lennium has seen a flood of other early finds, including the 6-million-
year-old
Orrorin tugenensis
unearthed by Martin Pickford and Brigitte
Senut, and the 3.5-million-year-old
Kenyanthropus platyops
dug up by
Meave Leakey, both found in Kenya in 2001.
51
No one knows whether
anamensis
,
ramidus
,
tugenensis
, or
platyops
is our direct ancestor: in a
