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Chapter Outline
Chapter 8
Hominid Origins and
Paleoanthropology
Paleoanthropology
‡
Paleoanthropologists reconstruct the
anatomy, behavior, and ecology of our
ancestors:
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Dating methods
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Definition of Hominid
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Geologists work with anthropologists to
locate potential early hominid sites.
Archeologists excavate the site and search
for hominid traces.
How do we “age” hominid finds?
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Early Hominids from Africa
Australopithecus from East Africa
‡ Early Homo
‡ South African Hominids
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Relative dating:
‡ Can tell you older or younger than
something else, but not by how much
‡ Based on laws of stratigraphy
ƒ Uppermost layer is “earliest” layer
Three characteristics significant in
defining hominids:
„ Large brain size
„ Tool making behavior
„ Bipedal locomotion
Relative Dating Techniques
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Stratigraphy - based on the law of
superposition, that a lower stratum (layer)
is older than a higher stratum.
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Fluorine analysis
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Applies to bone only
The longer a bone is in the ground, the more
flourine it will contain
Flourine is an element found in the earth’s
crust
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Relative Dating Techniques
‡
Biostratigraphy - related to changes in
the dentition of animals.
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Can trace changes in dentition fairly regularly
Can date rocks/geology by the types of
dentition in the strata
Major sites/geographic areas
Earliest Traces of
East African Hominids
The oldest specimen that is believed to be
a hominid comes from Lothagam,
northern Kenya.
‡ Several other fragmentary specimens
have also been found around the same
area of east Africa
Potassium/argon dating
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‡
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Traces “ancient compasses” based on historic
shifts in the magnetic poles of the earth
Where are these fossils
found?
The age of an object can be determined
by measuring the rate of disintegration:
„
Paleomagnetism - based on the shifting
of the geomagnetic pole
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Chronometric Dating Techniques
the only viable technique for dating very old (5 mya
– 1 mya) archaeological materials
Measures the rate of decay of potassium isotopes
into argon gas
Carbon-14 dating
‡
used in dating things such as bone, cloth, wood and
plant fibers that were created in the relatively recent
past by human activities.
The East African Rift Valley
Associated with faulting and volcanic
activity.
‡ Early sediments surfaced and located by
paleoanthropologists.
‡
Aramis – Middle Awash, Ethiopia
Dated at 4.4 million years old, this is the
oldest collection of hominids discovered.
‡ The remains provide anatomical evidence
of bipedalism, the criterion for hominid
status.
‡ The excavators suggested that the Aramis
hominids be assigned to a new genus and
species, Ardipithecus ramidus.
‡
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Laetoli - Tanzania
Laetoli footprints
‡
Dated at between 3.5 and 3.7 m.y.a.
Fossilized hominid footprints were found in
an ancient volcanic bed.
‡ Despite agreement that these individuals
were bipedal, some researchers feel they
were not bipedal in the same way as
modern humans.
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Hadar (Afar Triangle) - Ethiopia
Koobi Fora
(East Lake Turkana)
‡
Recovered:
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"Lucy" an Australopithecus afarensis female,
was recovered here.
Group of bones representing 13 individuals,
including 4 infants, suggest a social unit died
at the same time.
Some stone tools may be 2.5 million years old,
making them the oldest cultural evidence yet
found.
Likely make by australopithecus afarensis
Two hominids walking
side by side
‡ One with clear burden on
one side
(perhaps a child on a hip)
This site yielded the richest assemblage of
hominids from Africa.
‡ 150 hominid specimens recovered at
Koobi Fora represent at least 100
individuals.
‡ Hominids recovered include specimens
Homo habilis, Homo rudolfensis, Homo
erectus
‡
Olduvai Gorge
Central Africa
Louis and Mary Leakey conducted
continuous excavations from the 1930's to
early 1980.
‡ Paleontological evidence includes more
than 150 species of extinct animals which
can provide clues to the ecological
conditions of early hominid habitats.
‡ Homo habilis found here (the toolmaker)
‡
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A hominid mandible was discovered in
Chad dating from 3.5 to 3.0 m.y.a.
‡ Preliminary analysis suggests that this
fossil's closest affinity is to
Australopithecus afarensis.
‡ The fossil was found more than 1,500
miles west of the previously established
range of early hominids.
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South African Sites
The first australopithecine “the missing
link” between apes and humans was
discovered at a quarry at Taung (Taung
Child).
‡ As the number of discoveries
accumulated, it became clear that the
australopithecines were not simply
aberrant apes.
‡ The acceptance of the australopithecines
as hominids required revision of human
evolutionary theory.
‡
Australopithecine characteristics
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Anatomy and biology:
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Bipedal apes with modified dentition.
Hominid structure of teeth and jaws appear to
have required more grinding that an ape’s diet.
Males were larger in body size.
Australopithecines were social animals.
Australopithecines were principally vegetarian.
Australopithecines of 2 million years ago
occurred in 2 forms:
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More results from quarry activity
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Sterkfontein
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The most “prolific” fossil site in South Africa
Former quarry that “blew up” fossils to the
surface
Swartkrans
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The second most prolific site in South Africa
Robust vs. gracile australopithecines
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Robust Australopithecines
„ Larger body size
„ Small cranial capacities
„ Very large, broad faces
„ Massive back teeth and lower jaws
Gracile Australopithecines
„ Different face dentition
Gracile (means slender)
Robust
Early Homo (2.4-1.8 m.y.a.)
The earliest appearance of our genus,
Homo may be as ancient as the robust
Australopithecines.
‡ Leakey named these specimens Homo
habilis ("handy man")
‡ H. habilis differs from Australopithecus in
cranial cavity and dental proportions.
‡
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