Little Foot
BrendaB007 (brendab007@aol.com)
29 Jul 1995 11:21:27 -0400
By JOHN NOBLE WILFORD
c.1995 N.Y. Times News Service
Footprints preserved in volcanic ash show that human ancestors in Africa
were walking upright as early as 3.7 million years ago, making this
behavior one of their first and most distinctive departures from all other
primates.
But was bipedal walking the only way these protohumans got about? Were
they still climbing trees, in the manner of chimpanzees, for safety,
sleeping and gathering fruits and nuts?
These questions have long puzzled and divided anthropologists studying
crucial evolutionary changes in the early hominids, or human forerunners,
after their divergence from the apes.
Now the discovery of four foot bones in South Africa has produced the best
fossil evidence yet for the nature of ancestral locomotion, and may yield
compelling answers or simply rekindle the flames of old debates.
The four little bones, rather than settling the debate, have already
caused more fur to fly among the small group of contending experts who
study human origins.
In a discovery paleontologists describe as the most important in southern
African hominid exploration in recent decades, the four bones formed the
instep and the beginning of the great toe of a hominid that may have lived
as much as 3.5 million years ago, presumably a member of the
australopithecine genus.
This is the oldest set of connected foot bones of any hominid and the
earliest evidence, by more than half a million years, for the existence of
such ancestors south of tropical Africa.
But of greatest importance to the history of human evolution, analysis of
the bones, dubbed ``Little Foot,'' has revealed that this hominid combined
humanlike and apelike foot characteristics.
The weight-bearing heel and the springy arch of the foot were
unquestionably adapted for upright walking much like modern humans, said
paleontologists who examined the fossils, while the great toe was set at a
wide angle to the other toes and was highly flexible, presumably capable
of grasping and climbing.
In particular, the shape of the joint forming the ball of the foot
indicated that the big toe could rotate inward like the opposable human
thumb, useful in tree climbing.
In a report of their research being published in Friday's issue of the
journal Science, Dr. Ronald J. Clarke and Dr. Phillip V. Tobias,
paleontologists at the University of Witwatersrand in Johannesburg, said
the foot fossils were ``the best available evidence that the earliest
South African australopithecine, while bipedal, was equipped to include
arboreal or climbing activities in its locomotor repertoire.''
The scientists said that Little Foot strongly suggested that this early
ancestor was not exclusively bipedal, as are modern humans, but must have
been at home both on the ground and in the trees.
``The exact proportion of its activities spent on the ground and in the
trees is at present indeterminate,'' they said.
The bones were discovered in 1980 but their significance was not
recognized until last year. They were found in the deepest part of
sediments in the Sterkfontein cave, which is near Johannesburg and has
been the site of numerous early human discoveries.
The bones probably belonged to an early member of Australopithecus
africanus or another early hominid species, the paleontologists said. They
are the first connected bones found from the same foot of a single
individual of such creatures.
``This may be the kind of foot that made Mary Leakey's footprints,''
Tobias said in a telephone interview from Johannesburg.
He was referring to 3.7 million-year-old footprints embedded in hardened
volcanic ash at the Laetoli site in Tanzania. This trail of footsteps,
made by two or three individuals walking with an upright, humanlike gait,
was discovered in 1977 by scientists on an expedition led by Mary Leakey,
the prominent Kenyan archaeologist.
This represents the earliest indisputable evidence of hominid bipedality,
and it is usually attributed to Australopithecus afarensis, the species to
which the famous ``Lucy'' skeleton belonged.
Until recently, afarensis was the earliest known hominid species, but
still older hominid bones have recently been found in Ethiopia and
tentatively dated at 4.4 million years. Whether these hominids were also
bipedal, at least in part, has yet to be determined.
Most paleontologists had seen in the afarensis fossils clear evidence for
upright stance and bipedal walking, but several anatomists, notably Dr.
Jack T. Stern and Dr. Randall L. Susman of the State University of New
York at Stony Brook, have argued that the foot and ankle remains ``reveal
to us an animal that engaged in climbing as well as bipedality.''
Dr. Bernard Wood, a paleontologist at Liverpool University in England,
also has pointed out that Lucy's limb proportions and skeleton suggest
that she was neither predominantly tree-living nor fully upright. Writing
in the Cambridge Encyclopedia of Human Evolution, he said that Lucy and
her relatives might have ``spread out to forage on the ground in the day,
and then congregated, perhaps in caves or trees, at night.''
Clarke and Tobias acknowledged that their findings support the conclusions
of Stern and Susman that hominids of this period represented an
``intermediate degree of adaptation'' in locomotion.
Predictably, Susman in an interview praised the report as a ``conceptually
and theoretically very compelling paper.''
If the South African fossils are indeed of the africanus species, not
afarensis, the findings show, he said, that it is probably ``the blueprint
for all hominids'' that transitional species were part aboreal quadrupeds
and part ground bipeds.
``Fully committed bipeds,'' he said, probably did not emerge until Homo
erectus about 1.5 million years ago.
A leading proponent of completely bipedal early hominids, Dr. Owen Lovejoy
of Kent State University in Ohio, professed to be unshaken by the new
findings.
To him the Laetoli footprints had shown that the great toe of hominids had
already moved in line with the other toes and was no longer opposable,
indicating an individual who had clearly walked away from any four-legged,
tree-living past.
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In an accompanying article in Science, Lovejoy was quoted saying the
conclusions of Clarke and Tobias were ``patently absurd.'' He further
noted that the australopithecine hip, knee and spine had by this time been
adapted for an upright life and so to ignore that evidence in favor of one
foot joint was, in his words, ``mechanically and developmentally naive.''
When these comments were read to him, Susman said: ``That's just Owen
blustering. He still thinks hominids have to be a biped and nothing
else.''
Dr. William Kimbel, a paleontologist at the Institute for Human Origins in
Berkeley, Calif., said that it was ``conceivable to have primitive
features like the divergent big toe without implying that they are
maintained for the function of arboreal activity.''
In other words, he said, the new findings were not likely to satisfy all
scientists because of their differing views on interpreting the
relationships between morphology and function, particularly the function
of retained apelike characteristics.
Other paleontologists generally agreed that the research was an important
contribution to studies of early bipedality. But they expressed
reservations about the dating of the fossils at 3 million and possibly 3.5
million years old, as described in the report.
The age of Little Foot could be provoke other controversies. If it is 3.5
million years old and from the africanus species, Susman noted, this would
mean that it could not be a descendant of afarensis, which many
paleontologists have considered the common ancestor of all subsequent
australopithecine and eventually Homo species.
``There's enough in this paper to get everybody's blood boiling,'' Susman
said.
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