Olduvai Gorge (History)
The spot where the first A. boisei was discovered in TanzaniaOThe spot where the first A. boisei was discovered in Tanzanialduvai Gorge or Oldupai Gorge in Tanzania is one of the most
important paleoanthropological sites in the world and has been
instrumental in furthering the understanding of early human
evolution. This site was occupied by Homo habilis approximately 1.9
million years ago, Paranthropus boisei 1.8 million years ago, and
Homo erectus 1.2 million years ago. Homo sapiens is dated to have
occupied the site 17,000 years ago. Olduvai Gorge is a steep-sided
ravine in the Great Rift Valley that stretches through eastern Africa . It
is in the eastern Serengeti Plains in Arusha Region , Tanzania and is
about 48 km (30 mi) long. It is located 45 km (28 mi) from the Laetoli
archaeological site.
This site is significant in showing increased developmental and
social complexities in hominins . Evidence of this is shown in the
production and use of stone tools, which indicates the increase in
cognitive capacities. Evidence also indicates the practices of both
scavenging and hunting, which are highlighted by the evidence of
gnaw marks predating cut marks, and comparisons on percentages of
meat versus plant in the early hominid diet. Furthermore, the
collection of tools and animal remains in a central area is evidence of
increases in social interaction and communal activity.
History
Research
Researchers dated Olduvai Gorge using radiometric dating of the
embedded artifacts , mostly through potassium-argon dating and
argon–argon dating. German neurologist Wilhelm Kattwinkel traveled
to Olduvai Gorge in 1911, where he noticed many fossil bones of
an extinct three-toed horse. Kattwinkel's discovery inspired Professor
Hans Reck to lead a team to Olduvai Gorge in 1913. There, he found a
hominid skeleton, but unfortunately the start of World War I halted his
research .
In 1931, Louis Leakey found Olduvai fossils in Berlin and thought
Olduvai Gorge held information on human origins, and thus began
excavating there. Louis and Mary Leakey are the archaeologists
responsible for most of the excavations and discoveries of the
hominid fossils in Olduvai Gorge. Their finds, when added to the prior
work of Raymond Dart and Robert Broom , convinced most
paleoanthropologists that humans originally evolved in Africa. At the
Frida Leakey Korongo (FLK) site (named after Louis' first wife) in
1959, Mary found remains of the robust australopithecine
Zinjanthropus boisei (now known as Paranthropus boisei). The
specimen's age of 1.75 million years radically altered the accepted
ideas about the time scale of human evolution. They also found and
studied more than 2,000 stone tools and flakes at the site, which
were classified as Oldowan tools, in addition to an abundance of
faunal remains. Louis Leakey's son Jonathan found the first specimen
of Homo habilis, a jaw fragment, at Olduvai in 1960.
In the late 1990s and early 2000s, Professor Fidelis Masao of the
Open University of Tanzania led his team to excavate at Olduvai
Gorge. These researchers focused on stone tools and animal bones
bearing butchery marks to reveal the activities of long-ago human
ancestors. Masao also studied the rock art paintings found in the
region.
The geology of Olduvai Gorge and the surrounding region was
studied in detail by Richard L. Hay, who worked at the site between
1961 and 2002. His finding revealed, millions of years ago, the site
was a large lake, with shores covered with deposits of volcanic ash .
Around 500,000 years ago, seismic activity diverted a nearby stream
which began to cut down into the sediments, revealing seven main
layers in the walls of the gorge.
The name Olduvai is a misspelling of Oldupai Gorge, which was
adopted as the official name in 2005. Oldupai is the Maasai word for
the wild sisal plant Sansevieria ehrenbergii , which grows in the
gorge.
Occupation
Homo habilis is thought to have occupied the site from 1.9 to 1.2
million years ago. Paranthropus boisei was found to occupy the site
from approximately 1.8 million years ago until 1.2 million years ago.
Homo erectus remains were found and dated at the site from 1.2
million years ago until 700,000 years ago. Homo sapiens came to
occupy the gorge 17,000 years ago.
Significance
Toolmaking
In the 1930s, as Mary and Louis Leakey searched for earliest stone
tools in east Africa, many people were skeptical that Africa was the
place where humans evolved. Yet, when the Leakeys found tools in
Olduvai Gorge, evidence turned in their favor. These Oldowan tools
had sharp and shaped edges. Lithic flakes were taken off in the
intentional shaping of the tools' points.
The Leakeys recorded the particular locations in which the tools were
found and compared these positions to locations where the raw
materials originated. When these tools were found to have been
transported up to 9 miles from the materials' place of origin, this
suggested cognitive capacities to plan and think, and also to carry
materials. While these Oldowan tools were found in the same stratum
as the Australopithecus specimen, the multitude of other hominin
fossils found dating back to two million years ago complicated the
discussion of which species was, in fact, the toolmaker.
The first species found by the Leakeys, Zinjanthropus boisei or
Australopithecus boisei (renamed and still debated as Paranthropus
boisei), featured a sagittal crest and large molars . These attributes
suggested the species engaged in heavy chewing, indicating a tough
diet consisting of tubers , nuts, and seeds.
Conversely, the Leakeys' 1960s find held many different
characteristics. Firstly, its lack of sagittal crest and much more
rounded braincase suggested it was not an australopithecine. This
newer fossil's skull also suggested a much bigger brain capacity
than the previously found Australopithecus boisei. These stark
differences indicated this fossil must have belonged to a different
species, eventually named Homo habilis. Its cognitive capacity and
decreased teeth size identified Homo as the toolmaker.
The lowest (oldest) tools located were Oldowan which consisted of
pebbles chipped on one edge. Above this were true hand-axe ,
Chellean , and Acheulean industries. Higher still are located
Lavalloisean and finally the Stillbay implements. Mary Leakey
herself developed Oldowan A,B, and C linking them to Modes one
assemblages. Today her work remains a foundation for assessing
local, regional, and continent-wide changes in stone tool-making
during the early Pleistocene. It also helps to consider which species
of hominins were responsible for the changes in stone tool over time.
A significant change took place between Bed I and II at Olduvai Gorge
at around 1.5 m.y.a. Flake size increased, bifacial edges were present
more and their length increased, and signs of battering on artifacts
increased. The implications of these factors, among others, are that
after this pivotal time period hominids became better tool makers,
used tools more, and transported tools more.
Raw materials
To make Oldowan lithics in Olduvai Gorge, lava and quartz were
usually used. And only in specific period (1.65-1.53 m.y.a), chert was
used and it causes huge differences between the each assemblages
of Olduvai Gorge.
Hunters or scavengers?
Though substantial evidence of hunting and scavenging has been
discovered at the site, it is believed by archaeologists [who? ] that the
hominins that inhabited the area between 1.9 and 1.7 million years
ago spent the majority of their time gathering wild plant foods, such
as berries, tubers and roots. Though substantial archaeological
evidence for meat in ancient hominin diets exists, early hominins
were most likely not relying heavily on meat for nutrition . This
speculation about the amount of meat in their diets comes from
comparative studies with a close relative of early humans: the
chimpanzee . The chimpanzee's diet only consists of about 5% meat.
Furthermore, modern hunter-gatherers' diets also do not consist of a
large amount of meat. As a result, the majority of the calories in both
their diets came from plant sources. By the middle-range theory or
bridging arguments, it can be assumed that early hominins also had
similar diet proportions. These bridging arguments are used by
archaeologists to explain past behaviors and include an underlying
assumption of uniformitarianism . Much of the information about early
hominins comes from tools and piles of garbage from the sites such
as the FLK-Zinjanthropus (also known as FLK-Zinj and where the
"Zinj" skull was discovered) in Olduvai Gorge. Early hominins picked
special types of rocks that would break in a predictable manner when
"worked" to create tools, and carried these rocks from deposits
several miles away. By fitting rock fragments back together like a
puzzle, archaeologists, such as Fiona Marshall states in her article
"Life in Olduvai Gorge", have been able to determine the early
hominins, "knew the right angle to hit the cobble, or core, in order to
successfully produce sharp-edged flakes. Such flakes were used to
cut meat off animal carcasses. Shaped cobbles (called choppers)
were probably also used to extract the marrow from inside the bones,
or to chop up plant foods."
Bird , fish , amphibian , and large mammal bone fragments were found
at the FLK-Zinj site, some of which had marks on them. These could
have been made by hominins breaking open the bones for marrow,
using tools to strip the meat, or from carnivores which had gnawed
on the bones. Since both kinds of marks are present on them, some
archaeologists, namely Lewis Binford, think the hominins at FLK-Zinj
scavenged the meat or marrow left over from carnivore kills. Others
like Henry Bunn believe hominins hunted these animals and the
carnivores chewed on the bones left over. This controversial point
is still debated today, but archaeologist Pat Shipman's study proved
the evidence of scavenging was most common, meaning the majority
of carnivore teeth marks came before the cut marks. Other findings
during Shipman's research at FLK-Zinj revealed many of the
wildebeest bones found at the site were of an adult, male wildebeest,
and this indicates humans were hunting these animals, as carnivores,
such as hyenas , tend to hunt the weak, young and elderly. This
would indicate humans were not only scavenging, but hunting, as
well. The issue of hunting versus gathering at Olduvai Gorge is
clearly a controversial one. Further evidence found at nearby sites
helped to clarify some of this debate.
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