LAB 7 – LATE AUSTRALOPITHECUS
TO EARLY HOMO
AN 102, SPRING 2013
Today’s
class:
Quiz
Lecture
Lab
The genus Australopithecus
For each species, we will learn:
 The taxonomic name
 Its chronological age
 The site where it was found
 The traits it manifests
Gracile Forms
A. anamensis (EAST)
Robust Forms*
A. afarensis (EAST)
A. robustus (SOUTH)
A. africanus (SOUTH)
A. aethiopicus (EAST)
A. garhi (EAST)
A. boisei (EAST)
A. sediba (SOUTH)
* Sometimes placed in
genus Paranthropus
Australopithecus africanus
The first Australopithecus specimen was discovered by
Raymond Dart in South Africa in 1924.
It was a 4-year-old child.
 Dates from 3-2.0 mya
 Foramen magnum
anterior
 Flatter face, bigger brain,
smaller canines, nonsectorial P3
 400-500cc cranial capacity
“Taung Child”
Australopithecus garhi
 Discovered in Ethiopia in 1999
 Dates to 2.5mya
 450cc brain and very prognathic
face
 Bigger teeth than A. afarensis and A.
africanus
 Proportionally longer lower limb
bones
 At nearby localities, antelope bones
exhibited cut marks and damage
from hammerstones
 Important because it was previously
thought that no Australopithecine
made tools
Australopithecus sediba
 Discovered in South Africa
in 2008
 Dates to 1.977 mya
 420cc brain
 Small cheek teeth (Homolike!)
 Human-like hand and
pelvis
 More ape-like foot.
 Otherwise like A. africanus
 Demonstrates that there
were different ways to be
bipedal
Robust Australopithecines
A. anamensis, A. afarensis, A. africanus, A. garhi, and A.
sediba are all gracile Australopithecine forms.
Around 2.5 mya, a new group of Australopithecines
evolves: the robusts.
•They are found in East and South Africa
•Dental and jaw morphology differ from those of gracile
forms
•Specialized diet
Robust
Gracile
Robust Australopithecines
Robust Australopithecus species have:
 Larger cheek teeth/ very reduced
anterior teeth
Temporal
 Larger attachment sites for muscles fossa
involved in chewing
 Sagittal crest in males
 Broad, flaring cheek bones Postorbital
constriction
 Large temporal fossa
 Post-orbital constriction
In other words, robust species are highly
adapted “chewing machines”
Face
View looking
down on the skull
Robust Australopithecines
The attachment area of the temporalis muscle was larger in
robust Australopithecine forms than in modern humans
Australopithecus aethiopicus
•Found in Ethiopia
•Dates to approx. 2.5mya
•No postcranial bones
identified for sure in this and
other E. African robusts
“the black skull”
A. aethiopicus exhibits a mix of traits:
• Small brain and prognathic face (like A. afarensis)
• Sagittal crest and large molar teeth (like other robust
forms)
Australopithecus robustus
 South African form
Sagittal crest
 Dates from 2.0-1.5 mya
 500-530cc brain size
 Sagittal crest and other heavy
chewing adaptations
Temporal
Fossa
Large molar teeth
Flaring
cheek
bones
Australopithecus boisei
 East African form: First
found by Mary Leakey at
Olduvai Gorge in 1959
 Dates from 2.2-1.4 mya
 “Hyper-robust”
 Sagittal crest and other
heavy chewing adaptations
Very reduced
anterior teeth
 Very sexually dimorphic in
body size
 475-545cc brain size
Very large molars
with thick enamel
Kenyanthropus platyops
•The genus Kenyanthropus has only
one species and was named by
Meave Leakey, who discovered it
in northern Kenya in 1999.
•Dates to approx. 3.5mya
•Less prognathic face (like later
humans)
•Small brain (400-500cc), like
Australopithecines
•No definitive post-cranial fossils
•Relationship to Australopithecines
not entirely clear (could be a
regional variant)
Australopithecine behavioral
patterns
Locomotion
 All have bipedal adaptations, but some also retain adaptations
for climbing
Sexual Dimorphism
 Moderate canine dimorphism
 Moderate to high body size dimorphism
Suggests polygynous
or multi-male/multifemale social system
Development
 Faster to reach sexual maturity, less infant dependency than
humans; more than apes
Tool Use
 Some Australopithecines may have used stone tools (e.g., A.
garhi)
Australopithecine behavioral
patterns
Brain Size
 On average, 20% larger
brain than chimpanzees.
But, still considerably
smaller than humans.
A. africanus
A. robustus
Diet
 Herbivory and hard
seeds in robust forms
 A bit more omnivory in
gracile forms
Scratches = grainy
food items (leaves)
Pitted = hard
food items
(seeds, tubers)
Magnified tooth-enamel surface of
two australopithecines
Status and Body Size in
Australopithecines
Estimates show large differences in body mass and height
between male and female Australopithecines.
What are the phylogenetic relationships
of all these species?
Present
Modern
humans
Modern
chimps
Later Homo
(extinct)
Early Homo
(extinct)
Gracile
Australopithecines
(extinct)
Robust
Australopithecines
(extinct)
Ardipithecines (Sahelanthropus, etc.)
Past
Miocene Hominoids
Can we be
more specific?
One possible scenario….
time
Why do we have such
difficulty determining
this kind of phylogeny?
The Recovery Problem
?
?
?
time
Actual history of species
relationships
Recovered fossils (if we’re
lucky)
**A. sediba -
A recap of pre-Homo
hominid evolution
R
R
R
G
G
G
G
G
MOVING TO THE GENUS HOMO
time
Homo habilis
•The oldest known species of the genus Homo
•Louis Leakey discovered the first specimen at Olduvai
Gorge in Tanzania (where A. boisei was also found) in 1960.
OH 7 mandible
OH 7 hand
Homo habilis
Leakey was convinced this fossil was not A. boisei because:
•It had no sagittal crest
•It had smaller teeth
•It was found in close association with tools
Leakey named the new fossil Homo habilis, meaning “handy man,” in
reference to its presumed tool-making abilities.
-Leakey also emphasized the fact that his specimen had a
larger brain than any Australopithecine.
had a
HOMO HABILIS
Many paleoanthropologists rejected Leakey’s
new classification.
-They said the new fossil material was too
fragmentary to accurately conclude it
belonged in a new genus.
Richard and Louis Leakey
-They did not like the idea of “tool use” being
a criterion for naming a new genus.
Subsequently, Louis’s son Richard set up a new site at Koobi Fora in Kenya,
where he also found A. boisei and H. habilis.
-At the time, his finding solidified the taxonomy of H. habilis
-Today, some people argue that the name should be changed to A. habilis
due to post-cranial and developmental features.
Homo habilis
•H. habilis is found at sites in East Africa
•Dates from 2.4-1.5mya
Post-cranial features:
•Long, strong thumb
•Short, straight fingers
•Broader fingertips
Features
associated with
increased
manual
dexterity
Post-cranial materials
Found at Olduvai
Gorge in 1986
Homo habilis
A. africanus
Skull less rounded
Smaller brain (<500cc)
Prognathic face
Larger molars
More postorbital constriction
Homo habilis
Skull more rounded
Larger brain (600-700cc)
Less prognathic
Smaller molars
Less postorbital constriction
Homo habilis taxonomy
•Recently, some people have argued that based
on the variation seen in the cranial fossils, Homo
habilis should be divided into 2 species:
-Homo habilis
(smaller brains, less robust)
-Homo rudolfensis
(more robust with larger brains)
•Not yet agreed upon whether variation is more
likely within a single species or between 2, but
we will refer only to Homo habilis in this lab.
Homo erectus
•Eugene DuBois discovered the
first H. erectus fossils in Java in
1891.
•2 key specimens were
recovered: a skullcap and a
femur
DuBois
Homo erectus
•In the 1930s, Davidson
Black, Franz Weidenreich,
and Pei Wenshong began to
excavate at Zhoukoudian
(China)
•They uncovered over 100
fossils attributed to H. erectus
•Over time this has been a
very well-studied site
Homo erectus
H. erectus shows up in the fossil record
about 1.8mya
It is unequivocally different from any
prior hominid:
•It is bigger, and has a bigger brain
•It is found in sites outside of Africa
•It has more advanced tools
•Many of its features approximate
modern human traits
Homo erectus: Cranial Traits
•Significant increase in brain size
-Range of 750-1250cc
-Average of 900cc
•More encephalized than H. habilis, less encephalized than
H. sapiens
Homo erectus: Cranial Traits
Cranium
•Large browridges
•Low forehead
•Broad at skull base
•Nuchal or Occipital torus
•Thick cranial bones
•Shovel shaped incisors (also found in
some modern populations)
A. africanus
H. erectus
A. robustus
H. sapiens
Homo erectus: Post Cranial Traits
•As tall as modern humans
•More sexually dimorphic than modern humans
•Thicker long bones
H. erectus A. afarensis H. sapiens
Homo erectus and Homo ergaster
H. sapiens H. neanderthalensis
H. heidelbergensis
H. ergaster H. erectus
H. habilis
•Researchers often distinguish between H. erectus (Asian form) and H.
ergaster (African form.) For simplicity, I will refer to both as H. erectus,
although they do exhibit a few differences.
Time (millions of years ago)
% of resting energy allocated to brain
Increase in brain size and EQ in H. erectus
Homo erectus at Zhoukoudian
•Site occupied intermittently for
over 250,000 years
•Over 100,000 artifacts have been
collected
•Debates continue over how to
interpret some of these artifacts
Homo erectus in Africa (H. ergaster)
Paleoanthropologists have found
several nearly complete H. erectus
crania in East Africa.
•KNM-ER 3733: Dates to 1.8mya.
•KNM-ER 3883: Dates to 1.6mya
KNM-ER 3733
KNM-ER 3883
Homo erectus in Africa
A particularly famous H. erectus fossil was
discovered by Lake Turkana in 1984. It is
commonly known as Turkana Boy or
Nariokotome Boy
•Is over 90% complete
•Dates to 1.6mya
•Was 8-12 years old when he died (younger if
he grew in a more chimp-like way)
•Was 1.6m tall (5’ 3”), and likely to have
reached 1.85m (6’1”)
•Had a long, linear body shape like modern
humans
•Had a cranial capacity of ≈ 900cc
Homo erectus: World Traveler
•Since 1999, several H. erectus* crania were
unearthed at Dmanisi in the Republic of Georgia
•These crania date to 1.77 mya, making them the
oldest known hominins outside of Africa
•They are associated with Oldowan tools,
showing that H. erectus migrated out of Africa
with their toolmaking skills.
*Some have suggested a
new species, H. georgicus,
for these specimens
Homo erectus
Early
and
Later
migrations
Next time… Later Homo
Evolution & Tools
•Homo erectus is found in the
fossil record from 1.8mya to
200,000 years ago (possibly hung
around longer in East Asia)
•Toward the end of this time
period, another species of
hominid appears in the fossil
record, at 800 kya
•This species takes on an even
more modern appearance
H. sapiens H. neanderthalensis
H. heidelbergensis
H. ergaster H. erectus
H. habilis