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Hypothetical: A researcher claims to have found a hominin in a South African cave site that dates to the Early Pleistocene (~2.5-2 mya). They present an argument that this specimen showed evidence of a strict herbivorous diet that mostly comprised roots and grasses. They also suggest that, despite having a full suite of bipedal adaptations (including the convergent hallux), this animal was well-adapted to climbing trees. For the following response I would like you to:

-Explain how the researchers may have obtained the late Pliocene date

-What methods could be employed in this environment/region and why other methods would not work

-how do the methods work?

-Explain the craniofacial & dental morphologies that justify the dietary claim

-What are the traits and what are the functions of them?

-Explain what evidence might support the assertion that these animals were still adapted to climbing trees

-What are the traits and what are the functions of them?

-If you were to attribute this to a species (or even a grade), what would it be?

-Briefly contrast this specimen with other hominin forms at the time

Question #2

The emergence and success of our genus can be attributed to a variety of factors that likely began during the time of Late Australopithecus. This is most strongly associated with a shift in diet that not only influenced greater brain development but also a burgeoning tool culture. Furthermore, once this shift occurred, our ancestors became increasingly more mobile and rapidly refined stone tool technologies. This trend marks the story of our genus and leads to the continued success of our species,

Homo sapiens

.

First:

Explain the climatic conditions that may have influenced this dietary shift

Second:

Utilizing the hominin fossil record and your knowledge of the adaptive significance of each new morphology and technology, discuss:

-the presumed impacts of this diet on brain structure and function

-the original tool culture (structure and function) that emerged in response to this

Third:

Discuss the next wave of technological achievement and the Hominins associated with it. How did the development of Acheulean tools reflect a new way of hominin thinking?

Finally:

The pinnacle of hominin cognitive development is reflected only in

Homo sapiens

. What did this new material culture look like? Why do you think that this emerged only in African

Homo sapiens

and not in Neanderthals? Remember that the two populations had comparable cranial capacities.

Australopithecus
Savanna Adapted Hominins
Early Bipeds
ï‚´ There is very little evidence regarding the earliest
bipedal hominins
Sahelanthropus tchadensis
ï‚´ Sahelanthropus tchadensis
ï‚´ Orrorin tugenensis
ï‚´ Ardipithecus ramidus
ï‚´ Besides Ardipithecus, these fossil hominins are still
debatable
ï‚´ Either due to fragmentary remains or poor context
Orrorin tugenensis
Earliest Bipeds
 Ardipithecus ramidus (“Ardi”) is proven to be a biped
ï‚´ Dated between 4.5 and 4.2 mya
ï‚´ Anterior placement of foramen magnum
ï‚´ Iliac blades shaped and oriented for bipedal balance
ï‚´ Also retains primitive arboreal traits
ï‚´ Divergent hallux (big toe)
ï‚´ Disproportional hand/finger lengths
ï‚´ Good for climbing
Exiting the forest
ï‚´ Evidence from Ardipithecus suggests
that bipedalism first evolved in a
woodland environment
ï‚´ Arboreal and dietary adaptations
ï‚´ Generalized dental toolkit
ï‚´ Proportional incisors, canines, premolars,
and molars
ï‚´ No specializations
ï‚´ Isotopic analysis shows that it consumed
forest and grassland resources
ï‚´ Lived in a mixed environment
Exiting the
forest
ï‚´ Once hominins left the forest,
they needed to adapt to a
new resources base
ï‚´ Lack of soft resources to
consume
ï‚´ Fruit/young leaves
ï‚´ Moving to savanna
grasslands necessitated a
diet of grasses, roots, seeds,
or other tough resources
ï‚´ Dentition and masticatory
abilities needed to toughen
up
Australopithecus
ï‚´ Australopithecus is a fossil genus of hominin
ancestors adapted to savanna resources
ï‚´ More of a grade than a clade
ï‚´ No clear phylogenetic relationships
ï‚´ The grade is identifiable through a set of traits
ï‚´ Enlarged post-canine dentition
ï‚´ Premolars and molars
ï‚´ Thickened tooth enamel
ï‚´ Some degree of cranial traits associated
with heavy chewing
ï‚´ As they relate to the temporalis and
masseter muscles
Australopithecus
ï‚´
In addition to the dietary adaptation’s
australopithecines display a full suit of
bipedal traits
ï‚´ Not as efficient as modern
humans
ï‚´ But more so than Ardipithecus
ï‚´
Slow, lumbering bipedalism
ï‚´ Walking and standing
ï‚´ Not running
ï‚´
Some arboreal associated traits as well
ï‚´ Longer arms than legs
ï‚´ Long hands/fingers
ï‚´ Robust Ischia for hamstring
muscle attachment
Australopithecus
ï‚´ The aforementioned traits are
used to broadly identify
members of this grade
ï‚´ Diversity exists within the
grade
ï‚´ These hominins are dated
between 4.9-1.2 mya
ï‚´ More than 3.5 million
years
ï‚´ Multiple species existed
through this time
ï‚´ All had the general suite
of traits
ï‚´ Varied in modifications
Australopithecus
Diversity
ï‚´ The span of Australopithecus can be
divided into early and late phases
ï‚´ Early phase includes transitional
species and the archetype for a
generalized savanna dweller
ï‚´ Australopithecus anamensis
ï‚´ Australopithecus afarensis
ï‚´ Late phase illustrates a
divergence in the grade with
species specializing to different
savanna resources
ï‚´ Robust Australopithecines
ï‚´ Gracile Australopithecines
Savanna Resources
ï‚´ Savannas are a type of seasonal
grassland
ï‚´ Punctuated sparse woodlands
and gallery forests
ï‚´ Sharp contrast to the
environments characterizing most
of primate evolution
ï‚´ Available resources are tough to
chew and to digest
ï‚´ Grasses are abrasive
ï‚´ Roots and tubers are tough to
chew
ï‚´ Seeds and nuts can damage
teeth
Savanna Resources
ï‚´ Meat is another resource plentiful
on the savanna
ï‚´ Primates have never been
carnivorous
ï‚´ Insectivorous
ï‚´ Omnivorous with minimal
meat inclusion (small
vertebrates maybe)
ï‚´ Was not immediately
accessible or desirable
ï‚´ Savanna vegetation was
preadapted to
ï‚´ Fallback foods
ï‚´ Not entirely nutritious, but
plentiful
Early phase
Australopiths
ï‚´ The earliest member of this genus is
Australopithecus anamensis
ï‚´ Relatively fragmented fossil assemblage
ï‚´ Dates between 4.2-3.9 mya
ï‚´ There are a few elements that suggest
this was a biped
ï‚´ Anteriorly placed foramen magnum
ï‚´ Robust distal Tibia
ï‚´ Teeth tell a story of transitionary diet
Australopithecus
anamensis
ï‚´ Au. anamensis is interesting due to its
relatively broad incisors with enlarged postcanine teeth and thick enamel
ï‚´ Broad incisors are uncharacteristic of
the Australopithecus grade
ï‚´ Similar to Chimpanzees
ï‚´ Frugivore adaptation
ï‚´ The large post-canine teeth and thick
enamel suggest the inclusion of more
fallback foods
ï‚´ Abrasive diet
ï‚´ Au. anamensis is a mosaic fossil
ï‚´ Mix of primitive and derived traits
Australopithecus
afarensis
ï‚´
Au. afarensis is the best-known
Australopithecus species
ï‚´ Lucy
ï‚´
Also, the longest lived
ï‚´ 3.9-2.9 mya
ï‚´
Archetype of the grade
ï‚´ Best example of
Australopithecus adaptations
ï‚´
Post-canine teeth adapted to
abrasive resources
ï‚´
Bipedal with some arboreal
adaptions
ï‚´
Brain size on par with chimpanzee
(~400-500 cc cranial capacity)
Australopithecus
afarensis
ï‚´ Au. afarensis was a savanna generalist
ï‚´ Adapted to exploit various resources in its
environment
ï‚´ Likely contributes to its 1-million-year
existence
ï‚´ Towards the end of the time of Au.
afarensis, different specialized versions
begin to appear
ï‚´ Likely divergence from within Au. afarensis
ï‚´ Divergence stresses resource specialties
Australopithecus
divergence
ï‚´ Generalized populations have much
flexibility in generating specialists
ï‚´ Remember patterns of selection
ï‚´ Directional and disruptive selection
ï‚´ Acting on a range of variation
ï‚´ Some Australopithecus populations
began to heavily emphasize their
reliance on abrasive resources
ï‚´ Grasses, roots, seeds
ï‚´ Others found softer food sources
ï‚´ Though these required some ingenuity to
access
Robust vs Gracile Australopithecines
ï‚´ The are all Australopithecus
ï‚´ Some discuss robust
australopithecines in terms of
Paranthropus
ï‚´ Can only make such claims if you
can prove that they are related
(and thus belong in the same
genus)
ï‚´ We cannot do this
ï‚´ We keep them in the Grade
Australopithecus
ï‚´ This is especially true given the
flexibility of the traits used to
define the robust forms
Lumpers vs Splitters: What are you?
Robust
Australopithecines
ï‚´ There are three recognized robust
Australopithecine species
ï‚´ Australopithecus aethiopicus
ï‚´ ~2.5 mya
ï‚´ Ethiopia
ï‚´ Australopithecus boisei
ï‚´ ~1.4-2.3 mya
ï‚´ Tanzania
ï‚´ Australopithecus robustus
ï‚´ ~2-1.2 mya
ï‚´ South Africa
Robust Australopithecines
ï‚´ Robust Austrlopithecines
accentuated traits associated
with tough to process resources
ï‚´ Post-Canine Megadontia
ï‚´ Increased size of Premolars and
molars relative to Au. afarensis
ï‚´ Diminutive Incisors
ï‚´ Massive muscle attachments
ï‚´ Large, flared Zygomatics
ï‚´ Prominent Sagittal Crest
ï‚´ Post-Orbital Constriction/large
Temporal Foramen
Robust Craniofacial traits
Robust
Australopithecines
ï‚´ The prominent sagittal crest and postorbital constriction relate to enlarged
Temporalis Muscles
ï‚´ The enlarged Zygomatics provide
greater surface area for the Masseter
Muscles
ï‚´ Both muscle groups associated with
chewing force
ï‚´ The Post-Orbital Constriction and
Enlarged Temporal Foramen provide the
need space for the giant temporalis
muscles stretching from the sagittal crest
to the mandible
Gracile Australopithecines
ï‚´ Robust Australopithecines
exploited their niche successfully
for more than a million years
ï‚´ During this time, they co-existed
with other, less-robust hominins
ï‚´ Both in the genus
Australopithecus and Homo
ï‚´ These gracile forms shared many
similarities with Au. afarensis but
tended to have a smaller build,
smaller incisors, and a larger brain
Gracile
Australopithecines
ï‚´ There are a handful of tentative gracile
forms
ï‚´ Au. garhi
ï‚´ Au. africanus
ï‚´ Au. sediba
ï‚´ Some even place Au. afarensis in this
group
ï‚´ Essentially anything lacking the
specialized traits of the robust forms
ï‚´ We can be a bit more narrow, however,
to illustrate a change in form
Gracile
Australopithecus
ï‚´ The only strong evidence for a new
gracile form is found in Australopithecus
africanus
 Raymond Dart’s original find
ï‚´ ~2.9-2.1 mya
ï‚´ Australopithecus sediba would also
qualify but seems to be the same
species as Au. africanus
ï‚´ Variation
Gracile Australopithecus
ï‚´ Compared with Au. afarensis:
ï‚´ Smaller build
ï‚´ Slightly smaller cheek teeth
ï‚´ Larger cranial capacity
ï‚´ ~430-520
ï‚´ Smaller body with larger brain?
ï‚´ Increased encephalization
ï‚´ Why?
ï‚´ Brain growth facilitated by nutrient
intake
ï‚´ New food source?
ï‚´ Likely inclusion of animal protein
Meat Eating and Encephalization
ï‚´
Higher energy yield
ï‚´
Easier to digest
ï‚´ Reduction in intestinal tract
ï‚´ Energy conservation in digestion
ï‚´
More nutritious diet paired with reduced
energy requirement
ï‚´
Difficult to acquire
ï‚´ One strong benefit of being bipedal is having
free hands
ï‚´ Use of implements
ï‚´
Prior to the development of stone tool
culture (seen in genus Homo), gracile
australopithecines likely used stones as tools
to access bone marrow
ï‚´
Influenced lighter build and bigger brain.
The Genus Homo
Brain Changes
ï‚´ Gracile Australopithecines mostly
encompass two species
ï‚´ Australopithecus africanus
ï‚´ Australopithecus sediba
ï‚´ The likely inclusion of animal
protein resulted in
ï‚´ A smaller body (shorter
digestive tract)
ï‚´ Smaller teeth (easier to chew
food)
ï‚´ A larger brain (more energy
to fuel brain growth)
ï‚´ These traits trend into the genus
Homo
Our Genus
ï‚´ The genus Homo emerges during the
Australopithecus existence
ï‚´ ~2.4-2.3 Ma
ï‚´ Co-exists with multiple Australopithecus
species
ï‚´ Primarily recognized as having a smaller
build, smaller teeth, and larger brains
ï‚´ Morphologically very similar to later
gracile Australopithecines
ï‚´ Differentiated via stones tools
Genus Homo
ï‚´ Characterized by a rapid increase in
encephalization and the
accompaniment of recognizable stone
tool cultures
ï‚´ Tool culture vs. tools?
ï‚´ Some degree of uniformity
ï‚´ Method of development taught and
learned socially
ï‚´ Early tool culture (Oldowan) still pretty
crude
ï‚´ Function?
Oldowan Tools
ï‚´ Relatively simple tools
ï‚´ Hard to identify unless you
have a large sample
ï‚´ Stone core
ï‚´ Flakes removed
ï‚´ Creates an edge
ï‚´ Oldowan choppers
ï‚´ Simple tasks
ï‚´ Bone breaking?? Marrow
extraction??
Genus Homo
ï‚´ Homo habilis
ï‚´ Morphological and temporal
overlap with many Australopiths
ï‚´ ~2.3-1.5 mya
ï‚´ Tanzania
ï‚´ Encephalization jump
ï‚´ 510-630 cc
ï‚´ Au. africanus @ 430-520
ï‚´ Gracile skull
ï‚´ Reduced dentition
Finding Homo
ï‚´ H. habilis might be controversial but still represents the
start of a change
ï‚´ Somewhere around 2.5 mya:
ï‚´ Stone tools appear
ï‚´ Gracile austalopithecines disappear-ish
ï‚´ New gracile forms emerge with a larger cranial capacity
Genus Homo
ï‚´ Homo rudolfensis
ï‚´ N. Kenya
ï‚´ 1.9-1.8 mya
ï‚´ 700-750 cc
ï‚´ Both early homo species
associated with stone tools
ï‚´ +expanding
encephalization
ï‚´ Meat consumption offered
as an explanation
Variation
ï‚´ How many species?
ï‚´ H. habilis vs. H. rudolfensis
ï‚´ Minor morphological
differences
ï‚´ Sexual dimorphism??
ï‚´ Significant difference in
cranial capacity
ï‚´ 510 vs. 770
ï‚´ Probably a single species
ï‚´ Modern humans vary by at
least 400 cc’s on either side
of the scale
Last Morphological
Shift
ï‚´ Homo erectus
ï‚´ Many traits that carry over
from the initial trend
ï‚´ Broad brain case
ï‚´ Frontal and parietal
development
ï‚´ Expanded brain:: 8001,250 cc
ï‚´ Next step in bipedal
adaptations identifiable in
post-crania
Homo erectus
ï‚´ The development of modern proportions
was the last big step in our
morphological evolution
ï‚´ Thereafter evolution along trends
ï‚´ Nariokotome estimated at 5.3 ft tall
ï‚´ 1.6-1.5 mya
ï‚´ Longer stride made for easier travel
ï‚´ Pursuit of prey
ï‚´ Regional and Continental travel
ï‚´ Tool kit becomes more sophisticated
Homo erectus
ï‚´
As is the case with so many hominin
fossils, there is considerable debate
regarding the variation and/or
diversity of this species
ï‚´ Some propose a divide
between African and Asian
populations
ï‚´ Homo erectus vs Homo
ergaster
ï‚´
Throughout all of the debate, there
is very poor evidence supporting
the splitting of the one species into
multiple
ï‚´
Best diagnosis is that they are all H.
erectus and that this species was
variable across time and space
Acheulean Tools
ï‚´ Acheulean
ï‚´ Handaxes
ï‚´ Bilateral
ï‚´ Cognitive template
ï‚´ An idea of what the final outcome needs
to look like
ï‚´ H. erectus & the Acheulean spanned
distance and time.
ï‚´ More than 1.5 my
ï‚´ Africa, Europe, Asia
Archaic Homo sapiens?
ï‚´ Aka post-erectus grade
hominins
ï‚´ Homo heidelbergensis
ï‚´ ~600-800kya
ï‚´ Slightly increased cranial
capacity
ï‚´ ~1,300 cc
ï‚´ Advanced Acheulean
ï‚´ More refined
ï‚´ Increased fine motor skills
Neanderthal Split
ï‚´ Somewhere around 400-250kya
populations of H. heidelbergensis
migrated out of Africa
ï‚´ Colonized Europe during glaciation
ï‚´ Maintained advanced Acheulean tools
ï‚´ Mousterian
ï‚´ Developed physiological changes
adapted to cold climate
ï‚´ Increased robusticity
ï‚´ Increased respiratory
thermoregulation
ï‚´ Wider nasal aperture
Homo sapiens
ï‚´ Populations of H. heidelbergensis that
stayed in Africa continued evolving
ï‚´ ~300-200 kya
ï‚´ Homo sapiens
ï‚´ Developed more refined tool technology
ï‚´ Levallois::Prepared core
ï‚´ Something new
ï‚´ Art
ï‚´ Ochre at ~164 kya
ï‚´ Shell Beads at ~ 100
And then…?
ï‚´ H. sapiens developed more
sophisticated tools and
artistic expression in Africa
ï‚´ Neanderthals specialized to
Ice Age climates in Europe
ï‚´ ~45 kya wave of H. sapiens
migration into Europe
ï‚´ Not the first migration
ï‚´ But the first successful
ï‚´ Climate change + advanced
culture likely to have
influenced the replacement
of Neanderthals
Neanderthal DNA
ï‚´ Neanderthals are recent enough to
have preserved Ancient DNA (aDNA)
ï‚´ Genetically distinct from African Homo
sapiens
ï‚´ Of course they are, they were
geographically separated
ï‚´ Genetically distinct does not mean
separate species
ï‚´ Unique mutations occurred in
Neanderthal populations
ï‚´ Among other things, these account for
the different anatomy/physiology
Homo sapiens
neanderthalensis
ï‚´
Neanderthals represent a cross-roads
in the difficulties of species
identification
ï‚´ Paleospecies identified by
observable morphology in the
fossil record
ï‚´ Existing species identified via
reproductive continuity
ï‚´ Biological Species Concept
ï‚´
The unique segments of Neanderthal
DNA were inherited by modern H.
sapiens
ï‚´ We bred with Neanderthals
ï‚´ Same with the so-called
Denisovans
ï‚´
Homo sapiens was a variable
population
ï‚´ Just as it is now

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