Hominid
Fossils
Are
Likely
3.8
to 4
Million
Years
Old
A
team
led
by
Drs.
Yohannes
Haile-Selassie
and
Bruce
Latimer
of
the
Cleveland
Museum
of
Natural
History,
Cleveland,
Ohio,
has
been
conducting
a
paleoanthropological
survey
in
the
Mille-Chifra-Kasa
Gita
area
of
the
Afar
Region.
The
survey
was
conducted
under
a
permit
from
the
Authority
for
Research
and
Conservation
of
Cultural
Heritage
(ARCCH)
of
the
Ministry
of
Youth,
Sports,
and
Culture
and
was
financially
supported
by
the
Leakey
Foundation
and
the
Wenner-Gren
Foundation
of
the
United
States
of
America.
The
team
located
new
hominid-bearing
localities
in
the
Burtele
Kebele
of
Mille
district
in
Zone
One
of
the
Afar
Regional
State.
The
survey
team
has
designated
14
new
fossil
bearing
localities.
Three
of
the
localities
have
yielded
early
hominid
remains.
Major
fossiliferous
areas
are
around
the
Mille
River
east
of
Mille
Town.
Mille
is
520
KM
northeast
of
Addis
Ababa,
and
the
new
site
is
approximately
60
kilometers
north
of
the
famous
Lucy
site.
Several
additional
areas
have
been
documented
as
fossiliferous
although
localities
were
not
designated
and
fossils
were
not
collected.
THE
FOSSILS
The
survey
team
collected
a
number
of
fossils
that
were
exposed
on
the
ground's
surface.
In
their
exposed
position,
these
specimens
could
be
subjected
to
erosional
forces
and
had
to
be
collected
before
they
were
seriously
damaged
or
destroyed.
A
total
of
12
early
hominid
fossil
specimens
were
discovered,
including
parts
of
one
individual's
skeleton.
Portions
recovered
thus
far
include
a
complete
tibia,
parts
of a
femur,
ribs,
vertebrae,
clavicle,
pelvis,
and
a
complete
scapula
of
an
adult
whose
sex
and
stature
are
yet
to
be
determined,
although
it
is
already
clear
that
the
individual
was
larger
than
Lucy.
In
addition
to
this
discovery,
skeletal
parts
of
other
individuals
were
found
in
different
localities
in
the
area.
These
discoveries
include
isolated
teeth,
and
elements
from
below
the
neck
(arm
bones,
leg
bones,
phalanges).
The
non-hominid
fossil
assemblage
includes
animals
such
as
monkeys,
horses,
large
and
small
carnivores,
a
variety
of
antelopes
multiple
species
of
pigs,
giraffes,
rhinoceros,
elephants,
and
deinotheres.
Among
small
mammals,
porcupines,
cane
rats,
and
other
species
of
rats
were
discovered.
The
faunal
assemblage
also
includes
crocodiles,
fish,
and
hippopotamus.
GEOLOGY
AND
DATING
Exposed
sediments
in
the
new
fossiliferous
area
are
mostly
silty
sand
and
silty
clay
horizons
interbedded
with
a
number
of
volcanic
tuffs
and
basaltic
flows
suitable
for
dating.
The
total
section
in
the
area
is
estimated
to
be
about
50
meters
thick.
Geochronologist
Dr.
Alan
Deino
has
collected
16
rock
samples
and
the
most
critical
samples
above
and
below
the
fossiliferous
horizon
will
be
dated
soon
at
the
Berkeley
Geochronology
Center
in
Berkeley,
California.
The
estimated
age
of
the
site,
based
on
preliminary
field
analysis
of
the
associated
animal
fossils,
is
roughly
3.8
to 4
million
years.
However,
confirmation
has
to
await
radiometric
dating
of
the
rock
samples.
SIGNIFICANCE
Based
on
the
associated
animal
remains,
the
team
believes
that
the
hominid
fossils
are
likely
between
3.8
to 4
million
years
old.
This
will
place
the
new
fossils
in
time
between
the
earlier
4.4
million
year
old
Ardipithecus
ramidus
partial
skeleton
and
the
younger
3.2
million
year
old
"Lucy"
partial
skeleton
of
A.
afarensis.
The
team
hopes
that
the
new
discoveries
will
allow
scientists
to
connect
the
dots
--
furthering
our
knowledge
of
this
important
time
period
in
human
evolution.
Numerous
highly
important
scientific
issues
will
be
tackled
by
the
researchers
as
work
continues.
However,
it
is
already
clear
that
planned
scientific
studies
of
this
once
in a
lifetime
discovery
will
tell
us
much
about
how
our
four-million-year-old
ancestors
walked,
how
tall
they
were,
and
what
they
looked
like.
Haile-Selassie
says
that
it
is
too
early
to
tell
what
species
is
represented
by
these
hominids.
This
is
because
the
remains
are
embedded
in
adhering
silt
and
stone,
which
now
must
be
removed
under
a
microscope.
Comparative
studies
are
then
planned,
and
will
be
conducted
as
excavation
proceeds.
The
associated
plant
and
animal
fossils
and
embedding
sediments
will
also
be
subjected
to
study
by
specialists
in
order
to
further
refine
the
age
and
environmental
conditions.
FUTURE
PROSPECTS
The
team
emphasizes
that
this
discovery
and
its
announcement
represent
the
opening
of a
new
door
on a
poorly
known
time
period.
Years
of
research
lie
ahead.
The
new
fossiliferous
areas
are
very
promising.
There
is a
high
chance
of
recovering
more
fossil
hominids.
These
hominids
will
be
important
in
terms
of
understanding
the
early
phases
of
human
evolution
before
Lucy.
With
permit
from
the
Authority
for
Research
and
Conservation
of
Cultural
Heritage
(ARCCH),
the
team
will
continue
the
search
and
collection
of
additional
fossil
hominids
and
also
excavate
next
year
in
an
attempt
to
find
the
rest
of
the
bones
of
this
skeleton.
Africa is the
cradle of human race. Anthropologists have unearthed the oldest human
skeletons in East Africa in places
such as Hadar, Olduvai,
Laetoli. One of the
best preserved human remnants is a female skeleton found at
Hadar in Ethiopia. Anthropologists assembled about 40% of the young girl that was
given the nick name "Lucy". Lucy was dated between 3.8 and 3 million years
ago and belongs to the Australopethicus
category.
HADAR Hadar'spaleontological and anthropological significance
was discovered in 1968 by M. Taieb, a French
geologist. Taieb organized a geological and
paleontological survey of the area in 1971, in
which he was joined by D.C. Johanson, Y.
Coppens, and J. Kalb.
These workers formed the International Afar Research Expedition (INRE). They
chose Hadar from the many other available sites
to begin intensive investigation mainly because of its excellent
preservation of faunal remains.
During the initial field season in 1973 the first early hominid
fossils were recovered from Hadar, a knee joint
and a partial temporal. Nearly 6,000 fossils of mammals, a total of 87
species, were recovered in 1973 and in subsequent seasons. In the fall of
1974 a larger team returned to continue the search and soon made a discovery
of hominid teeth.
At the end of November D.C. Johanson
discovered at locality 288 the partial skeleton of a tiny female hominid,
which was nicknamed "Lucy." The 1975 field season brought even more hominid
remains, this time at Locality 333. This locality has been interpreted as
evidence for the catastrophic death of a group of hominids. The 333 site
yielded, by the close of excavations during the 1976-1977 field season,
hundreds of hominid fossil fragments derived from at least 13 individuals
representing all ages. All of the Hadar fossils
were returned after study to the National Museum of Ethiopia in Addis Ababa,
where they are permanently housed.
The Hadar Formation consists of at
least 280 m. of sediment. Over 100 stratigraphic
sections have been studied thus far, and it has been possible to subdivide
the sedimentary sequence into four stratigraphic
members. Radiometric dating has dated the top of the
Hadar units at ca. 2.9 million years (m.y.)
ago. Dating for the lower units has been more controversial, with estimates
3.6 and 3.3 m.y. ago. Thus it can be stated
confidently that the "Lucy" specimen is ca. 3 m.y.
old, while some of the other, stratigraphically
lower Hadar hominids are at least 3.3 and
possibly as much as 3.6 m.y. old. [Source: Ian
Tattersall, et al. eds,Encyclopedia of Human Evolution and
Prehistory(Chicago:
St James Press, 1988), pp. 239-241]
STONE-TOOL MAKING The
first humans used sharp stones as tools. "The emergence of a flaked-stone
technology during the course of hominid evolution marks a radical
behavioral departure from the rest of the animal
world and constitutes the first definitive evidence in the prehistoric
record of a simple cultural tradition, or one based upon learning.
Although other animals Archaeological evidence shows a
geometric increase in the sophistication and complexity of hominid stone
technology over time since its earliest beginnings 3-2
m.y. ago. Stone is the principal material found in nature that
is both very hard and able to produce superb working edges when fractured
A wide range of tasks can be performed such as
meat cutting and bone breaking". [quoted from
Tattersall et al.eds,
op.cit., p. 542].
Human Fossil Adds Fuel to Evolution Debate
Hillary Mayell
for National Geographic News
March 25, 2002
A one-million-year-old partial
skull found in Ethiopia has added new fuel to the human origins debate
among paleoanthropologists.
The skull cap and several other bones from seven individuals—all Homo
erectus— were found in a one-million-year-old layer of sediments known
as the Dakanihylo Member.
Ancient Controversy Do hominid fossils from one to
two million years ago represent a single species or numerous branches
on the family tree, some of which died out? A one-million-year-old
skull cap from Ethiopia rekindles the debate on this issue (above is a
reconstruction of a Homo erectus skull).
Photograph by Bettmann/CORBIS
Reporting in the March 21 issue of the journal
Nature, an international team of researchers says the skull provides
yet another piece of evidence that a single human ancestor, Homo
erectus, ranged across Europe, Asia, and Africa as long ago as 1.8
million years.
For the last two decades, the question of
whether fossils discovered from between two million and one million
years ago represent one species or numerous branches on the family
tree, some of which died out, has been a hot button of debate.
Tim White, a paleoanthropologist at the
University of California, Berkeley and co-author of the study in
Nature, believes the partial skull found in Ethiopia resolves that
question. "The matter of early hominid distribution and species count
is solved—one [species] at a million [years], from Spain to China to
Java to Africa," he said.
The skull, he said, represents an evolutionary
intermediate step linking older, more primitive forms of the species
with younger, more human-like forms.
Other experts, however, disagree with that
conclusion, and the issue remains controversial.
Piecing Together Fossil Evidence
The partial skull generating all the excitement
was found near the village of Bouri in Ethiopia in what is called the
Middle Awash study area. Based on fossils discovered in earlier digs,
hominids appear to have lived in the area for nearly six million
years.
Proponents of the "bushy tree"/multiple-species
view argue that African fossils dating to about two million years ago
belong to Homo ergaster. Homo erectus, the thinking goes, split off
about 1.6 million years ago, and existed only in Asia. The Asian
branch was an evolutionary dead end, and the species Homo erectus died
off.
Under this scenario, modern humans evolved from
the original African branch of Homo ergaster.
The caves and volcanic soil of Africa are
extremely conducive to fossil preservation, and scientists have been
able to accurately date African fossils. Fossils found in Eurasia and
Asia, however, are more difficult to date and until recently were
thought to be much younger than those found in Africa. "Java man" of
Indonesia, for instance, was originally placed in the 500,000-year-old
range.
The nearly one-million-year difference between
African and Asian fossils, along with the more primitive features of
the early African fossils, contributed to the idea that Homo ergaster
and Homo erectus were two species.
New technology has allowed for more precise
dating of fossils, and recent reassessments put the age of Java man at
about 1.5 million years old, contemporaneous with other fossil finds
in Africa. The age of fossils found in China has similarly been
revised upward.
In addition, the researchers found that even
taking precise measurements, it was impossible to differentiate
between the skulls from Asia, Africa, and Eurasia.
The Daka fossils show that as of one million
years ago, Homo erectus was probably a single species with gene flow
across its known range from Java to Italy to Ethiopia, concluded Henry
Gilbert, one of the study's co-authors and a biologist at the
University of California, Berkeley.
"Lumpers" and "Splitters"
The underlying definition of a species is a
group of organisms with common attributes, capable of interbreeding.
The question is, how different is acceptable?
Paleoanthropologists generally fall into one of
two categories based on their views of how much variation can exist
within species. "Lumpers," such as White and his team, believe there
can be a wide range of variation within a species. "Splitters"—the
"bushy tree folk," in White's term—regard the amount of variation seen
in the known fossils as indicative of different species.
Susan Anton, a paleoanthropologist at Rutgers
University, said human origins research is complicated because
scientists look at fossils across large geographic ranges and spans of
time, and try to reach conclusions based on morphological evidence
from a small number of fossils.
The situation is comparable to a researcher, one
million years from now, looking at a few fossil remains of an African
pygmy and an NBA basketball player. Both are members of the same
species, but their features represent a lot of variation within the
species. Without genetic or other supporting evidence, it's easy to
see how questions could arise among anthropologists of the future.
Anton takes a middle-of-the-road position on the
single-species versus multiple-species debate, saying she's willing to
consider "one species with some serious morphs."
Susan Anton, a paleoanthropologist at Rutgers
University, said the Ethiopian skull is "a great specimen and shows
some really neat things," but she is not convinced it bears out
White's claim that the fossil points to a single ancestor one million
to two million years ago.
Early African fossils, she explained, have
morphological characteristics that are very different from those of
island Southeast Asia. "The Daka fossil still shows very African
features," she said. "I was expecting the specimen to show more of a
mix of Asian and African morphology."
Fossils From Ethiopia
May Be Earliest Human Ancestor
David Perlman
San Francisco Chronicle
July 12, 2001
A team of scientists led by an
anthropologist at the University of California-Berkeley has discovered
the fossilized remains of what they believe is humanity's earliest known
ancestor, a creature that walked the wooded highlands of East Africa
nearly 6 million years ago.
The discovery, which occurred in the Middle Awash River Valley of
Ethiopia, is already challenging some existing theories about the
ancestral lineage of humans. It is also changing scientific views about
the nature of the environment that fostered the evolution of pre-humans
as they moved from verdant forests to open grasslands.
The team reporting the discovery in the July 12 issue of the journal
Nature was led by two Ethiopian scholars: Yohannes Haile-Selassie, an
anthropologist still working on his doctorate at the University of
California at Berkeley, and Giday WoldeGabriel, a geologist now at UC's
Los Alamos National Laboratory in New Mexico.
Discovery Site in Ethiopia
The dry washes of the Middle Awash River Valley in Ethiopia are home
to a recent discovery of what is believed to be the fossilized remains
of humanity's earliest known ancestor.
Copyright 2001 National Geographic Society
The fossils were gathered during four years of
demanding expeditions to a harsh and hostile Ethiopian scrubland where
lions and cheetahs hunt at night and few people roam the semi-desert
wilderness by day.
The remains include a jawbone with teeth, hand
bones and foot bones, fragments of arms, and a piece of collarbone.
But most important, the bones also included a single toe bone. Its
form provides strong evidence that the pre-human creatures walked
upright, the scientists said.
The toe bone is a crucial clue to the earliest
days of human evolution as it developed soon after the ancestral lines
of apes and humans split apart, perhaps 6 million to 8 million years
ago.
Lingering Questions
The fossils in Ethiopia were dated by Paul R.
Renne of the Berkeley Geochronology Center. Renne is a co-author of
WoldeGabriel's report in Nature.
Another co-author is Tim D. White, a
paleoanthropologist at UC-Berkeley who in 1994 discovered a pre-human
fossil, named Ardipithecus ramidus, that was then the oldest known, at
4.4 million years.
The latest fossils from Ethiopia vary in age
from about 5.2 million to 5.8 million years old, according to Renne.
Haile-Selassie has tentatively named the fossils Ardipithecus ramidus
kadabba, a subspecies of White's A. ramidus.
In January, a French team headed by Brigitte
Senut and Martin Pickford found fossils in Kenya that they dated about
5.8 million years old, from a creature they nicknamed "Millennium
Man." Pickford said the newly discovered fossils in Ethiopia are
"virtual contemporaries."
It's not yet clear where the fossils of
Haile-Selassie and WoldeGabriel belong on the family tree.
The world of paleoanthropology is highly
contentious, and scientists have been trying for many decades to sort
out the murky ancestry of today's human race by comparing thousands of
fossil bones and skulls. But no evidence is certain and no lineages
are clear.
Anthropologists call all the species and
sub-species of our ancient ancestors hominids, to distinguish them
from the ape lineage, which includes chimpanzees. The two
branches—apes and hominids—are believed to have separated and evolved
from one common ancestor between 6 million and 8 million years ago.
In a telephone interview from Addis Ababa, where
he is analyzing the fossils, Haile-Selassie said he is being extremely
conservative, and the fragments he and Wolde Gabriel plucked from the
sun-baked ground may represent an entirely new species of pre-human
creature.
"It could be the earliest hominid, or it could
be a common ancestor, or it gave rise only to the chimpanzee lineage,
or it went extinct around 6 million years ago without giving rise to
any species," he said.
Climate Factor
A major mystery in the story of human evolution
is how climate affected the environment where creatures that regularly
walked upright—the hominids—first emerged. Now, both sets of recent
finds—in Ethiopia and Kenya—could help resolve the puzzle.
One widely accepted theory holds that after the
ape and hominid lineages split, the earliest human ancestors were
forced into the expanding tropical grasslands of the African savanna
after the continent's thick forests dwindled as a result of climate
change.
But geochemical analysis of the ancient
sedimentary soils where Haile-Selassie's Ardipithecus creatures
lived shows that the region between 5 million and 6 million years ago
was well forested, well watered, and rich in woody plants, according
to anthropologist Stanley Ambrose of the University of Illinois, who
is also a chemist and a co-author of WoldeGabriel's report in
Nature.
The clear inference, according to Haile-Selassie
and WoldeGabriel, is that those early human ancestors of the Miocene
epoch were already thriving in the forests of a land that was then
being shattered by volcanic eruptions, and millions of years later was
to become the stony scrubland it is today.