Download Exam 1 set 4 Hominins

Extant Apes
Even though chimps look more similar
to gorillas and orangutans, they re
actually more closely related to
humans according to current genetic
data.
The facts most scientists agree on
Chimp vs. Human
Brains:
Chimp~320-350cc
Humans ~1350cc
Locomotion:
Chimp knuckle walking
Human habitual biped
What evolved in the hominins first:
large brains or bipedalism?
Look to the fossil record!
An Early Find
•  A nonscientist finds parts of a skull in a local
gravel pit near Sussex. Only the skull was
found.
•  It is somewhat human-like, and somewhat
ape-like.
•  The missing link!!!
•  Took the skull to scientists
•  The skull s features…
The Missing Link ?
• Small jaw like an ape
• Small molars like a human
• Large canines like an ape
• Highly vaulted skull like a human (big brain!)
• A mix of human and nonhuman ape characteristics
Fervor over the Missing Link
•  Yay! …Proof that Europe was the cradle of
humankind!
•  Moreover, the skull s large cranial vault suggested
that the European missing link was intelligent!
•  Despite some obvious error in the analyses, the skull
was celebrated for years.
…Found in England ~1908-1912 at the Piltdown gravel pit
Named it Piltdown Man
More fossils subsequently found
(these are 2-7 myo)
Sahelanthropus tchadensis
Found fossils 2001-2002 in Chad (about 100 years after
Piltdown man was found)
Sahelanthropus tchadensis Features
•  7-6mya
•  Found in center of Africa rather than East Africa and South Africa
where most research on human evolution has been conducted
•  Large jaw
•  Large browridge
•  Reduced canines
•  Large molars
•  Small brain~roughly the size of today s chimps at ~335cc; today s
humans are ~1350cc
•  Only skulls have been found, so we are not yet sure if Sahelanthropus
was bipedal
•  It is an unexpected mix of human and apelike features, and found in
an unexpected area: this is more evidence that hominin evolution did
not follow a simple progression from ape to human--rather, there were
probably many different hominin species that possessed a variety of
different adaptations
More fossils
•  ~4-2mya the hominins increased in number and
spread out in Africa
•  Multiple species lived at the same time
•  Roughly 2 categories; most found in south and east
Africa
–  Australopithecus (6 species) gracile type
–  Paranthropus (3 species) robust type
Australopithecus
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southern ape
Small bodies relative to humans
Clearly bipedal
Teeth, skull, jaw adapted to a generalized diet
Small teeth relative to Paranthopus
Chimp brain is ~335cc
Average Australopithecine brain ~500-700cc
Australopithecis afarensis
•  Clearly bipedal
•  The famous
Lucy
Laetoli footprints
c. 3.6 MYA
Footprints
made in East
Africa, probably
by A. afarensis,
several bipedal
creatures
walked across
a bed of wet
volcanic ask
about 3.6mya;
footprints were
preserved when
it dried
Australopithecus africanus
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Found in South and East Africa
Lived 2.2-3mya
Skeletons confirmed bipedality
High sexual dimorphism
–  Male canines bigger proportionately bigger than female
canines (like gorillas, etc.)
–  Males: 4 6 and 90 lbs.
–  Females: 3 9 and 66 lbs.
Taung child
(Australopithecus africanus)
-2.5myo
-discovered in S. Africa, 1924: the first
Australopithecine fossil ever found
Raymond Dart, an Australian anatomist living in
S. Africa (local workers in a mining pit brought it
to him)
-foramen magnum location like bipedal
humans, so Dart concluded it was a biped
-brain small like that of an ape
-rejected by scientists because at the time they
believed large brains evolved before bipedalism
(like Piltdown); with no postcranial skeleton,
foramen evidence not strong enough to prove
bipedality
How did they know it was a child?
It still had baby teeth and molars ready to erupt.
Gracile types: Genus
Australopithecus
Australopithecus africanus 2.5-2.6myo
Australopithecus garhi c. 2.5myo
Robust types: Genus
Paranthropus
Paranthropus aethiopicus c. 2.5 MYA
Paranthropus boisei c. 1.8 MYA
Paranthropus robustus c. 1.5-2 MYA
Paranthropus
•  parallel to man
•  Similar to Australopithecines from the neck
down (bipedal, short relative to humans)
•  Small brains
•  BUT they had massive molars and premolars,
and jaws adapted to chewing tough plant
materials; their skulls were modified to carry
the enormous muscles necessary to power
the chewing apparatus
Paranthropus
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Exceptionally large teeth, esp. molars
(unlike Australopithecus)
Exceptionally large jaws (unlike
Australopithecus)
Big teeth and big jaws mean:
Large jaw muscle (temporalis muscle) to
move the heavy, powerful jaw; jaw
muscles connect up and around the
sides of the head, and run underneath
the cheekbones to the jaw
Large jaw muscles mean:
–  Large zygomatic arches (cheekbones)
needed to create space for jaw muscle
–  More skull for the large jaw muscles to
connect to: a sagittal crest
–  Test yourself, clench your teeth and feel
your temporalis muscle--feel the muscle
where it stops, about an inch above your
temple
–  Sagittal crest
Black Skull (because it is black; just due to
the process of fossilization with high
manganese content):
Paranthropus aethiopucus
Paranthropus robustus and boisei
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P. robustus: wear marks on molars
indicate hard foods and nuts, but
research on fossil contents also
suggest a significant amount of
meat in the diet
• P. boisei: a super-robust
paranthropus
• P. robustus used to be called Australopithecus robustus and P. boisei used to
be called Australopithecus boisei
To summarize 4-2mya
•  Hominins spread around South and East Africa
•  Small brains (~500-700cc), but somewhat bigger than
today s chimps
•  Short
•  The GENUS Australopithecus is gracile
•  The GENUS Paranthropus is robust
•  Very sexually dimorphic
•  They are clearly bipedal.
The Evolution of Bipedalism
•  Several theories
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Walking on 2 legs is an efficient form of ground locomotion
Erect posture allowed humans to keep cool
It left the hands free to carry things
Allows for efficient harvesting of fruit from low trees
•  Different lines of evidence for and against these and
other theories
•  But one thing we know for sure:
Bipedalism evolved BEFORE big
brains/intelligence evolved
But wait, what about Piltdown Man???
Piltdown Man: A Hoax
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Skull fragments were of a human--hence the large brain
Jaw of an orangutan--hence the large canines
Molars were filed down to look like the small molars of a human
The signs were obvious, but, consistent with the prevailing notion in
England at the time, people wanted to believe that large brains
evolved prior to other features
They also wanted to believe that Europe was the location of humans
evolving from apes into modern humans
A set-back to science--a total waste of time
Forgery wasn t discovered until 1953! Though as early as 1915
other scientists had rejected it.
It did wane in acceptance with the finding of the Taung Child
The hoax is still cited by creationists in support of their view that the
theory of evolution cannot address the origins of man. Many cite it
as evidence of the frequent acceptance in the scientific community
of viewpoints with very little data.
Tools
•  Hominins have been making stone tools for at
least 2.5my
•  A particular kind of tool found in East and
South Africa dating back to 2.5 MYA:
•  Oldowan tools
Oldowan tools
Oldowan tools
-Several flakes can be
chipped from I core
-It is not clear if the
core was used as a
chopper of if the flakes
were used for cutting
-Experiments in
knapping (stone
toolmaking) have
shown:
-knappers were almost
certainly right-handed
-flakes were best at
processing carcasses,
though cores/choppers may
have been useful in other
activities
Question: Who was making and using them?
Who used Oldowan tools?
•  Probably Australopithecus and Paranthropus
–  We don t have direct evidence of these early hominin bones
associated with Oldowan tools, but that doesn t mean they
didn t use them (no one died and was fossilized with an
Oldowan tool in their hand, but we find the tools at the same
time they were alive, and we find clearly-processed animal
bones with the tools)
•  Definitely members of the genus Homo…
Homo
•  They were the first to leave Africa, and
they clearly used stone tools.
Final Group: Genus Homo
(includes us)
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Homo ergaster (African)
Homo erectus (Asian)
Homo heidelbergensis
Homo neanderthalensis
Homo sapiens (us)
H. ergaster
Several specimens have been found
H. ergaster
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Clearly a different genus from
Australopithecus and Paranthropus
Appear 1.8 mya in Africa (colder climate)
Disappear 600KYA
Bigger brains than earlier hominins ~800cc
Probably mastered fire
Probably hunted large game
Used Oldowan and Acheulean tools
Traits like modern humans: smaller, less
prognathic face, higher skull, smaller jaws
and teeth, similar body size, similar sexual
dimorphism
Other trait: very large brow ridges,
horizontal ridge at the back of the skull
(occipital torus) which allows a better biting
and tearing action with the incisors and
canines
Biting and tearing what? MEAT. Molars are
far smaller (and proportionately so) than
those of the earlier hominins who were
chewing and grinding hard plant foods
Homo ergaster c. 1.75 mya (Africa)
Acheulean tools
Acheulean hand axes
Regular, bifaced, teardrop-shaped flaked tooks; can have different
sizes (few inches to 2 feet have been found) and be made of
different materials, but always the same proportions; probably most
used for butchering, with less use for other tasks; 1.6mya to 300kya:
remarkable regularity of the tool industry for over a million years
Homo erectus
•  1.8mya-30kya
•  Very similar to H. ergaster but
–  found only in eastern Asia
–  Large brow ridges
–  Sagittal keel (a lump rather than
a crest) with unknown function
–  More sloped sides of skull
–  Used Oldowan tools mostly, but
a few Acheulean tools have
been found in eastern Asia, and
stone tools are absent from the
entire region above the latitude
line where bamboo grows
Homo erectus c. 1.6-0.7 MYA (Asia)
Neanderthals
Neanderthals
were shorter and
stockier than us.
Homo Neanderthalensis
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Only in Europe, 137-30kya
Adapted to cold environment: stalky, huge noses and faces
Large front teeth, many with cut marks
Well-adapted to hunting large game
We clearly did NOT evolve from them; genetic evidence shows they
were a separate branch that had a dead-end (I.e., they went extinct)
We know a lot about them because European paleoanthropologists did
a lot of digging there
First one found in Germany s Neander valley
LARGE BRAINS than humans, averaging 1520cc--bigger than us, who
average ~1350cc (though reflects large body size, and they are about
30% larger than us)
Probably buried their dead
Had short, brutal lives
Interesting fact: the patterns of injuries we see in Neanderthal bones
match those of human ________?