Dinosaurs | Egypt | Mesopotamia |Human Ancestors
The half scale replica is based on a skull discovered in 1975. The specimen was found at East Turkana by Mr. Bernard Ngeneo, a member of Richard Leakey's field expedition. The skull has the accession number KNM-ER 3733. KNM is an abbreviation for Kenya National Museum, and ER is the prefix given to all the specimens from East Turkana. This prefix was introduced prior to 1973 when Lake Turkana was known as Lake Rudolf, the name given it by Count Teleki when he first set eyes on the lake in 1888. The specimen is housed at the National Museum of Kenya.
At the time of its discovery, the skull was the most complete known for Homo ergaster. Previously none of the specimens had a face articulated with the cranium. It was not until the discovery of the 'Nariokotome Boy' that an associated skull and mandible of this species was found.
Overview
Homo erectus was first recognised in Java, when Eugene
Dubois discovered
a tooth, skullcap and femur in 1892. He named his discovery Pithecanthropus
erectus believing that the specimens represented a human ancestor that was too primitive
to be included in the genus Homo. Pithecanthropus means 'ape-man', and the
species name erectus reflects the very human-like femur which told Dubois that
this early human ancestor walked upright. It was not until 1960 that the name
Pithecanthropus was formerly revised to Homo. Subsequent to Dubois' discovery,
Davidson Black worked in the Chinese site of Zhoukoudian and in 1929 discovered
a skull cap more complete than Dubois' but very similar in shape. This was
followed by further specimens aswell as stone tools. Later finds by the in
Africa by the Leakey family were given the name Homo ergaster. The names ergaster and erectus have both been applied to the same finds, but ergaster is finding
more use lately to differentiate them from the later (and geographically distinct)
H. erectus.
The ergaster skull is quite distinctive. It has a much larger braincase than the australopithecines - almost twice as large as that of Australopithecus boisei, but smaller than Homo sapiens. The average cranial capacity for Homo ergaster is 910cc; the volume for KNM-ER 3733 is 850cc. Homo ergaster had a relatively small face, small teeth and weak jaw muscles. In many respects the skull is closely similar to Homo sapiens, but it lacks a high forehead and has prominent ridges (supraorbital tori) above the eye sockets. KNM-3733 is believed to be female because the brow ridges are thinner than in other presumed male specimens. Another Homo ergaster cranial character is the 'occipital bun', the distinct bun-shaped protrusion at the back of the skull. The mandible is more lightly built than that of the australopithecines, but it lacks the chin that is typical of Homo sapiens.
Hypervitaminosis A can be caused by eating raw carnivore livers which are rich in this vitamin. Early explorers in the Arctic and Antarctic who ran out of food and had to eat their dogs, frequently died from this disease not knowing why they were becoming sick. The East Turkana specimen provides an interesting insight into Homo ergaster behaviour. Not only does it confirm that H. ergaster ate meat but also, because the disease was so advanced, it shows that Homo ergaster was compassionate and cared for the sick.
Homo ergaster made quite sophisticated stone tools. The H. ergaster technology is known as the Acheulian Industry. Large flakes taken from large cores, were fashioned into sharp edged implements called bifaces (or handaxes). Bifaces are so versatile that they have been said to equate with a complex tool kit. They could be used to chop, cut, smash, beat and throw. Wherever Homo ergaster is known Acheulian tools are found, and wherever they are found they are very similar . The versatile tools enabled Homo ergaster to eat meat, a high calorie nutritious food. Brains require energy and the switch to a diet that included a significant proportion of meat provided the fuel to feed an enlarged brain. It was presumably this increased intelligence that enabled Homo erectus to live in the colder environments of Europe and Asia.
Homo erectus first appears in Europe and Asia almost immediately after it is first found in Africa. The earliest Homo ergaster in Africa is the skull KNM-ER 3733, dated at almost 1.8 million years. New dates suggest that Homo erectus reached Java sometime between 1.8 and 1.6 million years ago, and a Homo erectus mandible from Dmanisi in the Georgian Republic is believed to be of a similar age. It seems that Homo ergaster moved out of Africa almost as soon as it arose.
Important Finds
The first discovery of this species was made at Olduvai Gorge where Louis and
Mary Leakey recovered several specimens. One of these, OH 9, has thick, well-developed
brow ridges and a large cranial capacity. Another, OH 12, has a rather small
braincase and very thick skull. Richard Leakey, Louis and Mary's son, led many
successful expeditions which recovered specimens of Homo ergaster on both the
eastern and western shores of Lake Turkana in addition to the cranium KNM-ER
3733, and the mandible KNM-ER 992. The most spectacular discovery was the Nariokotome
boy, a skeleton of a 12 year old boy discovered by Kamoya Kimeu on the eastern
shores of Lake Turkana. This has provided more evidence relevant to this species
than any other single discovery.
Accounts of the discoveries of both KNM-ER 3733 and 992 are given in Richard Leakey's autobiography One Life. The description for the former was taken from Meave Leakey's diary and is quite detailed. Both accounts follow:
The discovery of KNM-ER 3733:
" August 1st.
Friday When Kamoya and his team returned to camp they reported that Ngeneo
had found a hominid brow ridge and maxillary fragments in Area
104..... Our curiosity was roused when we asked Kamoya if the brow ridge was
attached to a skull and he replied 'Well we cannot say because we can only
see a very small piece, most of it is buried.' Might it be a complete skull? "August
2nd. Saturday I went with Richard in the Toyota to see Ngeneo's brow ridge
following Kamoya and the team in their Land-Rover. They showed us the site
on the slope of a small gulley. There were two fragments of maxilla on the
surface and the frontals and the top of the orbits were just beginning to erode
out. It is impossible to say how much is there. The others all went off not
wanting to do any damage. Richard began to excavate the skull slowly while
I took photographs and collected the maxillary fragments and numerous other
tiny pieces of bone on the surface.
" The skull is in very bad condition with small plant roots growing through
numerous tiny cracks, but it does seem to go on back. Richard exposed part of
the parietals
and then left it to dry and harden. We returned to camp ..... After lunch Richard
went back to the skull with Kamoya and exposed some of the temporals and one
ear hole. It is an extremely slow job as the skull is so fragile and the ground
is wet from recent rain. There would be nothing left if it had eroded out naturally;
Ngeneo found it just in time, though how he spotted it I cannot imagine. There
is some matrix on it but the main problem is the numerous tiny roots which
get into the bone and break it up...
In the evening we covered the skull with an upside down metal basin and some
thorn bush before returning to camp. It would be terrible if an oryx trod on
it now!
" August 3rd. Sunday. Day in camp. Light rain. Rather cold.
" August 4th Monday. I went with Richard to the hominid skull. He worked on it
until 10.30. It looks as if it has a large cranial capacity and it may well
be complete. It is a very slow and difficult job though. We then went to see
where Kamoya had set up his camp. He had left with the team early in the morning
with enormous loads on the cars, but they had arrived safely. Richard went
back again after lunch to continue his excavation. Weather at last seems more
'normal'.
" August 5th. Tuesday. We returned to the hominid site and as Richard worked
the skull began to look all that we had hoped and very exciting... It is in
very bad condition with roots growing into the bone and everywhere the bone
is broken into tiny pieces which by some miracle still remain in their original
positions. Richard really has remarkable patience for this type of excavation,
and this specimen certainly needs it.
" Richard went back to the skull after lunch but he could not do too much
because it was so hot. We saw Kamoya had arranged for some of his team to start
sieving
the hominid site in the mornings...
Richard seems to have a temperature on and off, he puts it down to too much
sun while excavating. He has to fly to Nairobi tomorrow and has decided to
persuade Bob Campbell to come back with him to film the final stages of the
excavation.
" August 9th. Saturday. Richard arrived with Bob Campbell at about eleven o'clock.
After lunch we went to take out and film the skull. It came out well with no
disasters and the bone is now hard. It looks amazingly complete. An added bonus
is that the sieving has produced some teeth...
The discovery of KNM-ER 992:
" Despite the trouble we take to be methodical, sometimes the most exciting
finds are still pure accidents. One morning in 1971, for instance, three of Kamoya's
team were sitting round a sieve, quietly looking for tiny fragments of bone
from a hominid jaw that had been found several days before. Apart from the
low murmur of voices there was no other sound of human activity. It was a particularly
still and peaceful scene with the gentle rustle of the wind in the bushes and
the periodic call of the African Laughing Dove contributing to the mood of
tranquility. Suddenly a shot rang out and there was the unmistakable sound
of a bullet hitting the ground very close at hand. The three men at the sieve
fled for cover as fast as they could, running one hundred yards before they
reached a bush high up on a river bank. They hid there for at least an hour
and fortunately nothing else happened and they never saw a soul. As they came
out from under the bushes one of them almost trod on a complete fossil jaw
of a hominid partially exposed on the bank. Had they not scrambled up the bank
to hide after being shot at, that specimen would probably never have been found
and one more piece of the jigsaw of man's origins would have eluded us.
Preparation of KNM-ER 3733
Once the 3733 skull was back in Nairobi there was still a lot of work that
had to be done, cleaning the rock off the bone and gluing the tiny pieces
that had been collected in the field back together. Alan Walker, who has
remarkable skills in the reconstruction and preparation of fossils, and has
prepared many of the Kenyan fossil hominids, worked on 3733. Richard describes
the unusual problems with this skull in his autobiography One Life:
"One of the problems
with the new find, ....was that the inside of the braincase was completely
filled with very hard calcified rock. This made the
fossil extremely heavy and difficult to handle and had it fallen the impact
would have shattered it. In addition it was quite impossible to think about
reconstructing and attaching the delicate facial bones to the skull because
if the specimen were handled carelessly the excessive weight would certainly
crush them. How to remove this solid rock from the braincase posed quite a
problem. Normally, fossil skulls are found broken and so the question does
not arise or alternatively, if the specimen is relatively robust it is considered
reasonable to leave the rock inside the braincase.....
" Fortunately,....I had the assistance of Alan Walker......Alan has extraordinary
skills and has devoted months of his life to the tedious business of cleaning
rock off our more precious and fragile specimens. The challenge presented
by KNM-ER 3733 seemed to appeal to him and he was soon spending a great deal
of valuable research time working on the specimen. I was very curious to
know how he proposed to remove the rock from the inside of the skull, but
I decided to keep my silence until he was ready to tell me. His plan of action,
when he eventually disclosed it, came as quite a shock. He wanted to split
the skull into two or more large fragments by driving a large cold chisel
into the rock-filled braincase with a heavy mason's hammer!
" Alan went on to explain his plan in detail. First, he was going to cover
the outer surface of the skull with a number of layers of tissue paper, each
bonded on with a water-soluble glue. This was to produce a firm casing that
would prevent the skull from bursting or shattering when the chisel was being
driven in through the small opening at its base, the foramen magnum. The
rock in the immediate vicinity of this opening was to be drilled away as
far as was possible, making it easier to use the chisel. It all sounded perfectly
sensible but I confess I had terrible qualms. What was to happen if the skull
did shatter? 'Well' said Alan, 'at least all the pieces will be inside the
paper lining and we will simply have to put them all together again.'
" Over the next day or two the skull was duly covered with its paper jacket
and left to dry. Several days later Alan was ready and, assisted by Meave
and Tim White ...he set to work. I preferred to be away for the whole day.
The skull was firmly set down on a sand-filled bag while Alan operated the
mason's hammer and chisel. Blow after blow and nothing happened. Alan was
exasperated and finally put the chisel to the stone wall on the veranda and
with a very moderate blow he knocked off a huge flake of stone! A larger
chisel was purchased from a hardware store in town and soon after Alan had
obtained the result that he expected: the skull broke into three pieces and
the breaks were absolutely clean. Several weeks later, after Alan had removed
the rock from the inner surfaces, the pieces fitted back together again perfectly
and today there are no external signs that the fossil was subjected to such
extraordinary treatment.
Where it is found ?
Homo ergaster was the first human ancestor to move out
of Africa into Europe and Asia. This species is known outside Africa in China
and Java as Homo erectus.
Within Africa it is found in Ethiopia, Eritrea, Kenya, Tanzania and South Africa
East Turkana is part of the Turkana Basin sedimentary regime called the Omo Group deposits. These fossiliferous sediments were first discovered in the Omo Valley by a French expedition led by Compte de Boaz in the early part of the century. A series of expeditions have subsequently. The Compte collected a number of fossils and took them back to France for study. As a result, Professor Camille Arambourg undertook a larger expedition in 1930 when, over a period of two years he collected more than a hundred tons of fossils! During the war years Louis Leakey took advantage of British troop movements in southern Ethiopia to arrange for his assistant Heslon Mukiri, to spend a few weeks in the Omo Valley collecting for the Nairobi Museum and in the late fifties, Professor Clark Howell, arranged a short collecting expedition to follow up on the earlier work but unfortunately the Ethiopian border police confiscated all his fossils. It was not until Louis Leakey met with Emperor Hailie Selassie and persuaded him that an expedition to the Omo Valley might produce fossil human ancestors as important as those at Olduvai that a multidisciplinary International Expedition was mounted to the area led by Camille Arambourg (France), Clark Howell (USA) and Louis Leakey (Kenya).
The sediments to the east of Lake Turkana are known as the Koobi Fora Formation. Koobi Fora is the name given the area where the expedition built its base camp on a sandy spit by the lake shore. The sediments extend back to over 4 million years, but those between just over 2 and 1.3 million are the most richly fossiliferous and have yielded the greatest number of fossil hominids.
West Turkana, Kenya
West Turkana is part of the Turkana Basin sedimentary regime called the Omo
Group deposits.
Other sites where Homo ergaster has been found:
Fossil remains of Homo ergaster have been recovered at sites in Ethiopia, Kenya,
Tanzania and Eritrea. Many specimens have been recovered from the Omo Group
deposits to the west of Lake Turkana (known as the Nachukui Formation) and
in the Omo Valley (known as the Shungura Formation). Homo erectus has also
been recovered from other sites in East Africa including the Baringo basin
to the south of Lake Turkana, and Olduvai Gorge in Tanzania. Recently a complete
Homo ergaster skull was recovered by an Italian expedition in Eritrea. In
South Africa, specimens originally called Telanthropus , but now recognised
as Homo ergaster, have been recovered from Swartkrans.
Classification
There are differences in opinion as to what the correct name
for the African specimens should be. When Homo ergaster was first recognised
in Africa,
several researchers suggested that this was not the same species as that
found in
Java and China. In due course a new name, Homo ergaster was given to the
African Homo erectus and the mandible KNM-ER 992 was designated the type
specimen. Additional specimens have not resolved this issue and the difference
of opinion remains. We will use H. ergaster to represent the African material.
The classification of life is called taxonomy. The following shows the taxonomic sequence for Homo erectus:
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class Mammalia
Order Primates
Superfamily Hominoidea
Family Hominidae
Subfamily Homininae
Genus Homo
Species ergaster
Researchers
Field expeditions all over the world have led to the recovery of
the fossils on which we base the interpretation of human evolution. Homo
erectus and
Homo ergaster are known from many sites in Africa, Asia and Europe and
numerous field expeditions working in these areas have resulted in our current
knowledge
of this species.
Several famous names are associated with these discoveries because they organised the expeditions that found the most significant specimens. These include Eugene Dubois who found the first specimen of Homo erectus, Davidson Black who found the first specimens in China and Franz Weidenreich who continued Black's work on the Zhoukoudian excavations. Homo erectus has also been found at Swartkrans in South Africa, where John Robinson first named it Telanthropus. Louis, Mary, Richard, and Meave Leakey all worked on various East African expeditions along with co-workers Alan Walker and Kamoya Kimeu.
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