Human Evolution
The beginning: 10 million years ago in Africa
Climatic change. Getting
drier. Unbroken tropical
forests becoming a
patchwork of woodland
and savanna.
The split
• Sometime around 7 mybp east African primates began on an
evolutionary path distinct from central and west African primates.
• West was more densely wooded. East less so, more open. East
African primates went bipedal. Why? We don’t know
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Carrying babies?
Making tools?
Thermodymics?
Wading along shorelines?
Looking for predators?
More efficient movement?
Earliest hominins: pre-Australopiths
•Sahelanthropus tchadensis. (Toumai, “hope of life” in Goran). A single
skull, jaw fragments, several teeth, unearthed in 2002 by Michael
Brunet, dated to about 6.5 mybp Found in Chad, central Africa?
•Forward position of foramen magnum suggest bipedalism
Earliest hominins: pre-Australopiths
• Orrorin tugenenis “original man” in the local Tugen
language. February 2001, French researcher Brigitte
Senut, a few teeth and limb bone fragments in the Tugen
hills of Kenya, dated to about 6mybp
• Femur (valgus) angle suggests bipedalism
Earliest hominins: pre-Australopiths
• Ardipithecus kadabba found in the Middle
Awash region of Ethiopia, dated to around 5.5
mybp
• Ardipithecus ramidus (Ardi) remains are dated
to between 5-4.4 mybp; forest-dwelling,
bipedal, but at home in trees as well. No
evidence of knuckle-walking; is this derived
feature in great apes?
• Contros:
– Are kadabba and ramidus related?
– Are kadabba, orrorin, and sahelanthropus related?
– Ardi appears to have low sexual size dimorphism,
but australopiths have traditionally been thought of
as highly dimorphic species?
– Is Ardi the only one likely to be ancestral to Homo?
Earliest hominins: Australopiths
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Australopithecus anamensis, first uncovered in 1995 in northern Kenya
and dated to between 4.2 and 3.9 mybp. Descended from knuckle-walker
(terrestrial before bipedal?; contrast with Ardi.
Australopithecus afarensis (Lucy) found in the mid-1970’s by Donald
Johanson and dated to around 3.3 mybp, similar date for “Lucy’s child”
found at Dikika, Ethiopia, est. 3yrs of age.
Australopithecus africanus, Tung child found by Raymond Dart of the
University of Witwatersrand in South Africa, 1922. Dated as somewhat
more recent than Lucy
Australopiths
• Australopithecus sediba:
• Discovered in 2008 by Matthew
Berger (9 year old son of Lee
Berger). Not described until 2010.
South Africa
• Later australopith showing a mosaic
of australopith (teeth, limbs, upper
chest) and homo features (lower
chest, skull, face, pre-molars)
• A species at the transition point
between Australopiths and Homo?
• Dated to 2-1.5 mybp
Earliest hominins: Australopiths
• Lucy bones – unquestionably
bipedal. Some adaptations for
tree-dwelling present. Small 3-4
feet in stature. High sexual
dimorphism. Probably didn’t run
very well. Ate fruits, nuts, insects,
small USOs, amounts of meat.
Was prey as much as predator.
Earliest hominins: Australopiths
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Dart’s Taung child, killed by
predator? Dated at about
2.5mybp, est. 4yrs.
Period of nutritional stress at
2.5yrs, possible early weaning
age compared to apes; evidence
of cooperative breeding, care of
young?
Earliest hominins: Australopiths
• The pitted pattern of
Laetoli feet, about 3.5
mybp.
Earliest hominins: Australopiths
• Two general types:
• Gracile: Thinner boned, less powerful jaws, probably ate more
fruits, insects, etc. (ex. Africanus, afarensis)
• Robust: thicker boned, more powerful jaws, ridge crest on cranium,
flatter teeth, seed-crusher?, fibrous vegetable material (probably not
human ancestor; ex: Australopithicus or Paranthropus boisei and A.
or P. aethiopicus)
Earliest hominins: Australopiths
Summary: Time period 5-1mybp,
robust later than gracile.
Robusts may have made
stone tools, but little evidence.
High sexual dimorphism, male
– male competition. Small
family – female bonded
groups, single male. Bipedal
but well adapted to trees.
Forest, waterside dweller.
Chimp-size brain, robust a
little larger. Probably restricted
to Africa. Bipedal apes.
Early Homo
• Homo habilis: Unearthed 1960’s Louis Leakey. Olduvai Gorge in
northern Tanzania. Larger brain size (640cc; note chimps are about
400cc). Evidence of simple stone tools found also (Oldowan tools).
• Homo rudolfensis: 1970’s Richard Leakey. Brain size 750cc, but
with more primitive looking face. Both dated to around 2.3-2.0 mybp
The Oldowan tool kit
• Simple stone tools made by
striking a hammer stone against
a core to make a shape flake
(cores may also have been used
occasionally as tools). 2.6mybp
Hand/Brain and tool manufacture
Pad to side grip: thumb to side of
index finger
Three jawed chuck grip: thumb,
index, middle finger (baseball
grip)
Five jawed cradle: thumb against
four fingers
Lucy could use these grips, apes
generally cannot. Pounding,
digging (USOs), throwing.
Oldowan tools probably not, but
maybe robusts later.
What Lucy could not do:
Oblique power grip: fourth and fifth
fingers in ulnar opposition to
thumb, used for holding and
swinging clubs and hammers
Hand/Brain and tool manufacture
• Pet scans of Oldowan
knapping: visual-motor
coordination
• Primary motor cortex
• Somatosensory cortex
• Dorsal visual pathway
(occipital/superior partietal)
• Cerrebellum
• Little frontal lobe activation
Knapping apes
• Kanzi knapping studies
• Produces “oldowan-like” tools, but not using percussion
technique
• Less power; less precision and selectivity
• Percussion technique requires
motor control beyond that of
nonhuman apes. Some
advance in planning perceptual
motor skills.
• Some evidence of adjustment
in ongoing flaking process
(Lokalalei site, northern Keyna)
• Probably not a big cognitive
advance.
Homo erectus/ergaster
• “Nariokotome boy”:
1984 Richard Leakey.
Near complete
skeleton of 12 year
old boy, west of Lake
Turkana in northern
Kenya, dated to
around 1.4mybp.
Nariokotome
• 1984 the bones of
an 11 ½ year old
boy were found
under a tree along
a dry stream
channel west of
Lake Turkana
Homo erectus/ergaster
The earliest evidence for
controlled use of fire comes from
the 790,000-year-old site of
Gesher Benot Ya'aquov, Israel,
as depicted in this illustration
• Erectus/ergaster probably emerged
around 1.8mybp in Africa.
• Evidence of a quick expansion out of
Africa into East Asia (1.7mybp) and
Southeast Asia (1.5mybp).
• Some argue that Asia derivative should
be ‘erectus’ and African should be
‘ergaster.’
• Fully committed biped.
• Much larger brain: NB = 900cc
• Much lower sexual size dimorphism (in
human range)
• Larger, more cooperative social groups
• More meat in diet
• Use, maybe control of fire
• Around 1.4mybp – emergence of new
tool technology: Acheulen tools.
A tale of two species: African ergaster and Asian
erectus
• African ergaster:
– Ergaster migrated out of African almost as soon as it emerged.
– The ergaster that remained in Africa either (a) slowly evolved
into modern Homo sapiens or (b) went extinct, leaving Africa to
be re-colonized by descendants of Asian erectus who eventually
evolved into modern Homo sapiens
A tale of two species: African ergaster and Asian
erectus
• Asian erectus
remained in extreme southeast Asia until as recently as 20,000 ybp
(Homo florensiensis – ‘the hobbit’)
Evolved into Homo heidelbergensis in Eurasia (500,000ybp) who
eventually gave rise to Neanderthals and quite possibly Homo
sapiens
H. heidelbergensis very likely migrated extensively throughout
Europe, east Asia, and possibly Africa. Probably the first true biggame hunter.
Homo heidelbergensis
• 350,000 to 500,000 YA. The Homo
heidelbergensis Skull Atapuerca 5 was
discovered in Spain in 1992 by Juan-Luis
Arsuaga, in the fossil-rich caves of Sima
de los Huesos (Bone Pit), Sierra de
Atapuerca, This site has thus far yielded
over 5000 fossil hominid remains.
Although somewhat smaller than other H.
heidelbergensis, this individual is
considered among the most complete
premodern skulls ever found. The cranial
capacity is 1125 cc.
Summary of Hominin Species
Acheulean Tool kit: emerges about 1.4-7mybp
• Larger tools, more specialized, exemplified by the hand
axe
• Later versions of hand axe (.5mybp) suggest an image
to guide tool creation, attention to symmetry and shape.
Some may not have been strictly utilitarian.
Evolving mental capacities
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Boxgrove debitage
(400kybp)
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Berekhat Ram
(230kybp)
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Levallois “prepared
core” technique
(300kybp
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Pigment use
(300kybp)
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Control of fire
(300kybp)
Composite tools: 300,000 ybp
• Tools with multiple components: (1) point, affixed
to a (2) shaft, using a (3) binder. Extended
construction processing possibly requiring the
same type of sequential motor planning
necessary for language.