Assignment 7- Hominid’sThis assignment requires that you watch the video linked below and answer the questions. This video gives a fascinating look into early hominids. I selected questions that will overlap with your text, Notes Pkt. and powerpoint slidesA couple of years ago Zeresenay Alemseged spoke at the Bowers Museum in Santa Ana about his find of Salem. Salem is an Australopithecus afarensis, the same species as Lucy. Lucy was on exhibit at the museum at the time (yes, the actual Lucy of 3.2 million years ago, shipped all the way from Ethiopia, I’m such an anthro nerd I saw her 4 times!). BecomingHuman- First Steps Questions-. Your answers don’t have to be long, but make sure you accurately and completely answer the questions. Some of the answers are in the text, notes pkt. or ppt slides for Ch 10. 1. What is a hominid (see Ch 10 ppt) and what features identify a hominid in the fossil record?2. What was the environment of the Rift Valley like when Salem lived? 3. Which of the models for bipedalism do you think are most likely? Briefly state why you favor that model(s) (texbook and video).4. What is competitive exclusion (ppt slides, text)? 5. What is the molecular time clock? When did we last share a common ancestor with chimps? (text, ppt slides and video) What process of evolution provides the changes that are counted in the molecular time clock?
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Ch 10 Evolution of Early Hominids
This section we will focus on the
origin of the hominid fossil record.
This chapter will be covered on
Exam 2 and on the final (exam 3)
Human beings seem
quite incapable of
themselves & their history
emotional in one way or
another Ernest Mayr
There are no final words.
Human origins will always
Origin and Evolution of Primates
Origin of Anthropoidsmonkeys, apes, humans
Climbing in trees
Evolution of New World Monkeys
Rafting from Africa
Migration from North
Why are these
hypotheses and not
What hypothesis does the
Where do stories of monsters come from?
Primate Evolution Tree
Where do we come from?
What are we? Where are we going?
What is a hominid? A human or human like ancestor.
How do we know a fossil is a hominid? Look at the parts of the body
affected by bipedalism; foramen magnum, pelvis, knees, feet, hands
(not weight bearing).
When we no longer used our hands
for locomotion, it allowed our hands to
become more flexible, to have the
refined opposability which we use to
Our feet lost the opposable toe,
and prehensile ability, and
became solid platforms of support
What do you see in the primate
feet and hands below?
Foramen magnum- what does the position of the
foremen magnum tell us?
It is rare to find toes, or complete
hand or feet bones. They are
small and delicate. It is much
more common to find skulls, or
femur bones, which are large and
less likely to be crushed or lost.
If a skull is found, the position of
the foramen magnum (hole where
the spinal column enters the skull)
gives insight into whether creature
was a biped or quadroped.
Our skull is balanced on top of our
head. Animals which move
primarily on four limbs, have the
foramen magnum angled back.
Below see the pelvis of a chimpanzee, an Australopithecus, and a
human. Apes have a longer, narrower, flatter pelvis. Humans, who
need more muscle attachments for their legs, have a wider, shorter,
Humans have a narrow
stance to give balance. We
can lock our knees which
chimps cant do.
When Donald Johanson
found Lucy (the famous
he first saw the knee bone,
and his question was what
is a human knee doing in a
layer some 3.2 million years
old? But it wasnt a human
The first change that defines the difference between hominids and ape
ancestors is bipedalism. The second major change that occurred and
can be identified in the fossil record is in the teeth.
In general the trajectory for hominids has been
towards smaller teeth and chewing muscles.
There are also differences in the dental row,
canines, enamel thickness, etc. between apes
We do share the same dental pattern with old
world monkeys, and apes; incisors, canines, pre
molars and molars (2-1-2-3)
Hominids have a curve shaped dental row,
whereas apes are more U shaped.
Apes have extended canines and a
Can you determine which teeth are apes
and which are humans? What dental
pattern is intermediate?
What led to the selection for bipedalism?
How would each process of evolution
Mutation- introduces variation
Gene drift- in small populations
can randomly bring alleles to
100% or 0%
Gene flow- if its stopped, it can
be the first step of speciation. It
shares alleles between
Natural selection- selects for
traits in relationship to fitness
(reproductive success) and the
What role would the
In what environment did
bipedalism evolve in?
When was bipedalism
5-7mya shared a common
Fossil and genetic data
Models to explain the
selection for bipedalism
What are the different hypotheses or
models used to explain the evolution
Is it likely only one model played a
role, or several of them?
Walking in trees
What sources of data can we use to test
We can test the efficiency (calories
used) for walking on two or four
We can observe when apes walk
upright, and its often when they are
Who is the oldest hominid ancestor?
To answer this we need to define a hominid and what
criteria we use to determine if a creature is a
hominid (see earlier slides)
Questions exist regarding the species below. Are they
hominids? The key is whether or not their fossil
remains reveal they were bipeds or quadropeds
The debate for the species listed above is ongoing.
Who is our oldest hominid ancestor? Keep in mind
how rare fossils are, it is likely we will never find the
definitive oldest hominid. However, we will likely
continue to collect data and the debate will shift. At
this time it is generally agreed that Australopithecus
anamensis is the oldest definitive biped and
therefore the oldest hominid ancestor.
To the right is an artists reconstruction of how they
might have looked. They likely retained the thicker
hair of most primates, their face is prognathus
(lower face juts out), were small brained, but
walked on two legs.
Australopithecus (genus)- bipedal apes
This genus has many different
species and spanned a long
time period, roughly 4.2-1.7
million years. It is found only
in Africa. You need to know
the specific species listed in
the Notes Pkt. along with the
general info on this genus.
Genus description: Small
brained gracile cranial
features, mixed fruit/vegetable
diet, mixed bipedal/arboreal
Why do you think they are
called bipedal apes? What
is ape like about them? Its
their brains they have
small, ape sized brains, but
theyre hominids because
they are bipeds.
Found in Africa, 2.7-1.2 mya
Genus description: Small brained robust
cranial features (seasonal fallback
foods), mixed grassland, vegetable diet,
mixed bipedal/arboreal traits
You dont need to know any of the
species for this genus, but you do need
to know about the genus in general.
Below the neck they are similar to the
Australopithecus, but above the neck
they are different in their teeth and
chewing muscles. The environment was
changing and a selection for larger
chewing muscles and teeth allowed
them to survive roughly a ½ million
years longer than the
What led to multiple hominin speciations and extinctions? What does
evolutionary theory tell us? What role does competitive exclusion and
the environment play in speciation and extinction?
Evolutionary theory reveals that
speciation and extinction are two
common themes of the history of life
on earth. The hominid fossil record
reveals many speciations and
Environment change is a big driver of
evolution. What was the environment
doing during the evolution of our
Australopithecus and Paranthropus coexisted for a couple of million years.
Paranthropus out lived
Australopithecus by rough ½ million
years. What physical changes allowed
them to survive as the climate was
changing and drying?
Was it competitive exclusion that led to
the extinction of Australopithecus?
The genus Homo evolves in this
timeframe as well. Well cover them in
60 minutes Australopithecus sediba
Watch this video
discovery of A. sediba
A. sediba- Donald Johanson and Richard
Leakey debate taxonomic classification
Johanson and Leakey have
debated, and argued about the
interpretation of the fossil
record for many decades.
They are both big players in
taxonomic interpretation do
you favor (and why)?
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