ANTA01H3 Lecture Notes - Lecture 8: Ibm 7090, Orrorin, Tugen Hills

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Published on 6 Nov 2015
ANTA01 – Lecture 8 – Australopithecines & their Ancestors
Today’s Objectives
Early hominid traits & early species
Learn about species of gracile australopithecines
Learn about species of robust australopithecines
The Hominin Fossil Record
The fossil record is always fragmentary and can be problematic
We need specific conditions for fossils to actually form, and we need to find these spots
and start digging which is very time-consuming and expensive
What we typically find are durable tissues
oWhat looks like a bone but is a rock
oThe hardest bones in our body are our teeth because of the enamel coating on
the outside
We can see how big the animal is and what the animal ate by looking at
oMost post-cranial material don’t survive
Relatively small animals
Animals that weren’t immediately buried
We have to use anatomical features to distinguish hominins from fossil apes
oSpecific adaptations like evidence of bipedalism and dentition
Hominin Dentition
Anything with human like traits or intermediate traits are hominins
Ape-like traits were apes not hominins
Some dental traits
oDental arcade
Shape of your tooth row
In humans: there is a parabolic arch (we have smaller teeth overall)
In apes: broader in the front and it is more U-shaped because they have
larger canines
In early hominins: something in between humans and apes – smaller
anterior dentition than an ape but it is still U-shaped
Face shapes (prognathism where the lower face is sticking out)
Humans have a flatter face
oTooth size and shape
Any primates or mammals are heterodonts which means we have
different teeth for different functions (this is represented in our dental
Lizards and lower vertebrates are all homodonts (basically only for
grabbing and bolting food)
For hominins we are looking for a slow reduction in size and shape
oCP3 Complex
Sometimes called the sectorial premolar complex
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It is a gap in the lower jaw that accommodates the large canine coming
down so animals with large canine and close their mouth
As the canine comes down and sits at the spot, it gets sharpened since it
is located at the third premolar
Present in monkeys and apes
Hominins should be experiencing a loss
Canine is reducing in size (gap is reduced or completely absent)
The outer coating of the teeth
Apes have thin enamel because they eat soft foods like fruits and spinach
All hominins have thicker enamel because they eat harder foods
Except earlier hominins
Thicker enamel probably arose multiple times to adapt to their diet
Enamel alone does not make a hominin
oCranial Crests
It Is an increase in brain size and a decrease in facial size
An emphasis on intelligence
Loss of masticatory chewing
A loss of crests!
Humans do not have cranial crests
On the split of chimpanzees which happened 6-7 million years ago
We used to not have many of these specimens until about 10-15 years ago
Early hominins only show some of these features which is why it is very difficult to
distinguish early hominins from fossil apes
oSahelanthropus tchadensis
oOrrorin tugenesis
oArdipithecus ramidus & kadabba
Arboreal Retentions in early hominins
Things we should be seeing:
oAdaptions to an arboreal environment
They should have relatively long arms compared to legs and slender, curved fingers and
The big toe is relatively away from the foot
oThis took a long time in human evolution
They may have also spent a lot of time in trees to be safe from predators
oExample: when we see a bear our first instinct is to climb a tree
Very possible they weren’t a habitual terrestrial biped
First Hominins
Many come from east Africa known as the Great Rift Valley
oA woodland area
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First hominization was in the late Miocene apes
oBut there is very little evidence in this 10-6 million years ago time period
oWhat were found were controversial
Sahelanthropus tchadensis
It is very controversial
Described in 2002
6-7 million years’ old
oMakes it the potential oldest hominin
Found in Chad which is outside of East Africa
People criticized the dating wasn’t right
In this area, what was found were evidence of amphibians, aquatics, forest dwellers, and
They call it the Toumai Child
oToumai refers to children being born too close the dry season making it less likely
to survive
Why is it controversial?
oPosition of foramen magnum is a little intermediate
A little bit back to which you can say it is a full biped
Also had some modern hominin traits
oLack of prognathism, small canines, and a non functioning CP3 complex, no
Also had some ape like traits
oSmall brain, U-shaped dental arcade, thin enamel
The cranial deformation makes the assessment on what it is difficult (not sure if it is a
hominid or an ape)
Orrorin tugenesis
Means “original man”
Found in Tugen Hills which means it is not a controversial area
6 million years
What was found: 12 fragments of finger, arms, partial mandible, teeth, and femur
oThere was no skull
oThe femur indicated bipedality
The habitat was woodland
Hominin features
oThe femur, the thick enamel, relatively small molars
Ape features
oLarger upper canines
The arm and femur anatomy is not evidence of bipedality is the final criticism even
thought it is larger than expected and the femur anatomy may support bipedality
Found in the Afar Triangle, Ethiopia which is not a controversial site
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