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Lucy’s feet were
made for walking
By Bruce Bower
A tiny 3.2-million-year-old fossil found in
East Africa gives Lucy’s kind an unprecedented toehold on humanlike walking.
Australopithecus afarensis, an ancient
hominid species best known for a partial female skeleton called Lucy, had stiff
foot arches like those of people today,
say anthropologist Carol Ward of the
University of Missouri in Columbia and
her colleagues. A bone from the fourth
toe — the first such A. afarensis fossil
unearthed — provides crucial evidence
that bends in this hominid’s feet supported and cushioned a two-legged stride,
the scientists report in the Feb. 11 Science.
“ We now have the evidence we’ve been
lacking that A. afarensis had fully developed, permanent arches in its feet,” Ward
says. Survival for Lucy and her comrades
must have hinged on abandoning trees
for a ground-based lifestyle, she proposes.
The new fossil confirms that members of Lucy’s species could have made
3.6-million-year-old footprints previously found in hardened volcanic ash at
Laetoli in Tanzania (SN Online: 3/22/10),
she says. A. afarensis lived from about
4 million to 3 million years ago.
Scientists have argued for more
than 30 years about whether Lucy and
her kin mainly strode across the landscape or split time between walking and
climbing trees.
News of arched feet in these hominids
follows a report that a recently discovered A. afarensis skeleton dubbed Big
Man, though footless, displays long legs, a
relatively narrow chest and an inwardly
curving back—all signs of a nearly
humanlike gait (SN: 7/17/10, p. 5).
“There were far too many highly
detailed adaptations in every part of the
A 3.2-million-year-old Australopithecus
afarensis fossil curves like the match-
ing bone in the human foot below it.
A. afarensis skeleton for upright walking
and exclusive ground travel not to have
emerged,” remarks anthropologist O wen
Lovejoy of Kent State University in Ohio,
who studied Big Man’s remains.
In fact, Lovejoy says, a walking-adapted
foot much like that attributed to Lucy’s
kind by Ward’s group had already evolved
by 4. 4 million years ago in the early hominid Ardipithecus (SN: 1/16/10, p. 22).
Though Ardipithecus had an opposable
big toe incapable of propelling a two-legged gait, he argues that this creature
could have walked using its other toes.
Based on the new find, A. afarensis
does appear to have had arched feet,
remarks anthropologist William Jungers
of Stony Brook University School of
Medicine in New York. But other foot
features — including long, curved little
toes — indicate that a skeletal system for
upright walking had not fully evolved in
Lucy’s kind, Jungers asserts.
Humans could outrun Neandertals
Homo sapiens’ heels more suited to long-distance trotting
Achilles tendons. The
runners displayed short
lower heel bones, even
shorter for those who used oxygen
most efficiently.
By Bruce Bower
Stone Age humans, unlike Neandertals,
had heel bones spring-loaded for long
runs, a new study suggests.
In ancient Homo sapiens, as in people
today, a short lower heel stretched the
Achilles tendon taut, say anthropologist
David Raichlen of the University of Arizona in Tucson and his colleagues. That
arrangement increased the tendon’s
springlike action during running and cut
energy consumption, the scientists report
in a paper published online January 26
in the Journal of Human Evolution.
Raichlen’s team calculated oxygen
consumption for eight
experienced distance
runners running on
a treadmill at 16 kilo-
meters per hour. On a
separate day, an MRI
scanner took images of
each man’s heels and
Heel-bone measurements of 13 fossil
Homo sapiens that lived between about
30,000 and 100,000 years ago resemble
those of today’s runners, the scientists
say. On average, the measurements indicate that the ancient humans expended
6. 9 percent more energy while running
than their counterparts today did — not
a substantial difference, the researchers say. Heel bones of seven Neandertals
from the same period indicate that these
hominids used an average of 11. 4 percent
more energy while running than the modern athletes did, a statistically notable
disparity, Raichlen says.
Raichlen’s study
“provides a new line of
evidence that Neandertals were not as adept at
long-distance running as
modern humans were,”
remarks anthropologist
Herman Pontzer of
Hunter College in New
York City.
Heel bone length (red, in
modern runner) helped
early humans run more effi-
ciently than Neandertals.
