Washington,
DC (3/21/01)- A 3.5 million year-old hominid skull recently discovered
in Kenya could lead to a major rethink of mankind's earliest origins. The
skull appears to be that of not merely a new specie, but possibly an entirely
new genus, says Meave Leakey
of
the National Museums of Kenya.
Right: Skull
of the
Flat-Faced Man of Kenya, Kenyanthropus platyops
Credit:
photo by Fred Spoor, copyright National Museums of Kenya.
Leakey and colleagues discovered the nearly complete
skull on the arid shore of Lake Turkana in northern Kenya. The resemblance
of the skull to modern humans is said to be its most striking feature. The
discovers have dubbed it Kenyanthropus
platyops - the Flat-Faced Man of Kenya. Until now, many paleontologists
believed the oldest human ancestor to be Australopithecus afarensis,
popularly known as Lucy, after the partial female skeletal remains discovered
in Ethiopia in 1974. The 'Flat-Faced Man' is contemporaneous with Lucy, suggesting
a possible alternative ancestry for humans.
"Kenyanthropus shows persuasively that at least two lineages of early
human relatives existed as far back as 3.5 million years. The early stages
of human evolution are more complex than we previously thought," said
Leakey in a statement issued by the National Museums of Kenya.
While the two hominids may have lived in the same time and place, they are
remarkably different. The skull of Kenyanthropus, for example has a
much flatter face than Australopithecus. The new new skull also has particularly
small molar teeth. The researchers speculate that the two hominids may have
had separate diets and did not compete for food.
“We’ve always assumed Lucy was our ancestor and now we need to
re-evaluate that idea. In the absence of any other fossils in the time between
about 3.8 million and 3 million years ago, the only possible human ancestor
that could be claimed was Australopithecus afarensis. Now that we have
a new form of early hominid from the same time period that is quite distinct
from afarensis, the anthropologists will have to decide which of these
forms of early human actually lies in our ancestral tree. It cannot be both,”
said geologist Frank Brown, dean of the College of Mines and Earth Sciences
at the University of Utah.
The Kenyanthropus platyops skull was discovered in August 1999 by
Kenyan research assistant Justus Erus, who noticed a tooth protruding from
the mudstone sediment. It is the oldest known, nearly complete cranium of
any form of early human. The skull is similar to an earlier discovery known
as 'skull 1470' that was found in the eastern Turkana basin in the 1970s.
Called Homo rudolfensis by some and a member of genus Australopithecus
by others, the most recent discovery suggests it might actually be a descendant
of Kenyanthropus.
"The discovery indicates that at almost every time in the past back
to 4 million years, there were two or more species of hominid existing on
Earth. So where we used to see a very simple ladder of evolution from one
form to the next, the current thinking is that the evolutionary history of
man and manlike creatures is more like a bush with many dead ends and only
one stem that leads all the way to us," explained Brown.
The research appears in the March 22, 2001 issue of Nature.
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