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Chapter 13

Chapter 13- From Hominin to Homo.docx


Department
Biology
Course Code
BIOLOGY 1M03
Professor
Jon Stone
Chapter
13

Page:
of 11
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Chapter 13: From Hominin to Homo
-about 1.8 ma, a new creature called Homo ergaster appeared
overy similar to humans in that these developed slowly, and infants must
have been helpless at birth
olarge, robust bodies with long legs and short arms
committed to life on ground
oprobably learned to master fire and to hunt large game
ohave smaller brains that humans do, and their subsistence technology
seems to have been much less flexible than ours
Hominins of the Lower Pleistocene: Homo ergaster
-Pleistocene epoch began 1.8 mya and saw a cooling of world’s climate
odivided Pleistocene into three parts: Lower, Middle, and Upper
lower
1.8 mya
sharp cooling of world’s climate
middle
sharply increased fluctuations in temperature and first
appearance of immense continental glaciers that covered
northern Europe 900 kya
upper
ended about 12 kya when a warm, interglacial phase of
world climate began
-Homo ergaster appears in African fossil record about 1.8 mya and disappears 0.6
mya
ofossils found in Ethiopia, Tanzania, Kenya, and South Africa
omost paleontologists assigned these African fossils to the species Homo
erectus, but a growing number of paleontologists have come to believe
that African specimens have become too distinct
onew name given was Homo ergaster or “work man”
-Homo ergaster appeared in Eurasia about the same time it was first known from
Africa
oHomo ergaster was the first hominin to make its way out of Africa
know this because there was a discovery of a lower jaw and
Oldowan tools in sediments dated to 1.1 or 1.8 mya in Georgian (at
archeological site Dmnaisi)
also uncovered two nearly complete crania at Dmnaisi that are very
similar to African specimens of H. ergaster and dated around 1.7
mya
H. ergaster migrated out of Africa to Eurasia about 1.7 mya, taking their
tools with them
Morphology
-skulls of H. ergaster differ from those of both earlier hominins and modern
humans
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2
oretain many of characteristics of earlier hominins (marked narrowing
behind eyes, receding forehead, no chin)
oalso show many derived traits, some of which are shared by modern
humans
smaller , less prognathic face, a higher skull, and smaller jaws and
teeth
oalso has some derived traits not shared by humans
horizontal ridge at back of skull (occipital torus)
large brow ridges
oderived traits are probably related to diet
better adapted for tearing and biting with canines and incisors
less suited for heavy chewing with molars
teeth are smaller than australopithecines and paranthropines, but
molars are reduced relatively more in comparison with incisors
ohas substantially larger brain than earlier hominins
average brain volume was about 800 cc (larger than brains of
earlier apelike hominins- 500-700 cc)
olarger body than earlier hominins
-Postcranial skeleton of H. ergaster is much more similar to skeleton of modern
humans that to that of earlier hominins, but it still differs from ours in interesting
ways
ofound skeleton where fossils of Australopithecus anamensis,
Paranthropus aethiopicus, and Kenyanthropus platyops were also found
skeleton of the H. ergaster was named KNM-WT 15000
oKNM-WT 15000 had same body proportions as people who live in tropical
savannas today: long legs, narrow hips, and narrow shoulders
also had short arms, compared with earlier hominins
quite tall and also robust and heavily muscled
infants probably matured slowly and were dependent on their
mothers for a long period of time
mother’s birth canal was same as it is in modern humans
sexual dimorphism was reduced
males were about 20% to 30% larger than females, making
them less dimorphic than apelike hominins and only slightly
more dimorphic than modern humans
may not have had spoken language
vertebral canal in thoracic region of back is larger in modern
humans than in apes, and it contains proportionally thicker
spinal cord
studies show that extra nerves that enlarge spinal cord
innervate muscles of rib cage and diaphragm
othe KNM-WT 15000 probably had less precise control
over muscle of his rib cage and diaphragm
was first hominin that could run for long distances
may be useful in long-distance scavenging and hunting in
open country
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-H. ergaster may have developed more rapidly than modern humans
oresearchers estimate that H. ergaster developed more slowly than
australopithecines but still faster than modern humans
if this is true, that means H. ergaster did not have same long
childhood period as humans
suggests that learning was not important in lives of creatures
still uncertain whether this is true
Tools and Subsistence
-H. ergaster made fancier tools than earlier hominins had made
oassociated with Oldowan tools
oaround 1.6 to 1.4 mya in Africa, H. ergaster added a new kind of stone tool
called a biface
biface
omost common type of biface is called a hand ax (shaped like a teardrop
and has a sharp point at narrow end)
ocleaver: lozenge-shaped biface with a flat, sharp edge on one end
opick: thicker, more triangular biface
obifaces are classified as Mode 2 technology
call the Mode 2 industries of Africa and western Eurasia (Europe
and Middle East) Acheulean industry
suggests that toolmakers had a specific design in mind
Mode 1 tools of Oldowan industry had a haphazard appearance; no
two are alike
ohand axes have regular proportions: ratio of height to width to thickness
Implies makers had shared an idea for design
-Hand axes were probably used to butcher large animals
-hand axes were designed for:
1. butchering large animals
2. digging up tubers, burrowing animals, water
3. stripping bark from trees to get at nutritious cambium layer
underneath
4. hurling at prey animals
5. dispensing flake tools
-from experiments, Schick and Toth conclude that hand axes are best
suited for butchery
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