Title: Human Evolution The beginning: 10 million years ago in Africa
1Human EvolutionThe beginning 10 million years
ago in Africa
- Climatic change. Getting drier. Unbroken tropical
forests becoming a patchwork of woodland and
savanna.
2The 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
dont know - Carrying babies?
- Making tools?
- Thermodymics?
- Wading along shorelines?
- Looking for predators?
- More efficient movement?
3Earliest 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
4Earliest 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
5Earliest 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?
6Earliest hominins Australopiths
- 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-1970s by Donald Johanson and dated to around
3.3 mybp, similar date for Lucys 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
7Australopiths
- 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
8Earliest hominins Australopiths
- Lucy bones unquestionably bipedal. Some
adaptations for tree-dwelling present. Small 3-4
feet in stature. High sexual dimorphism. Probably
didnt run very well. Ate fruits, nuts, insects,
small USOs, amounts of meat. Was prey as much as
predator.
9Earliest hominins Australopiths
- Darts 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?
10Earliest hominins Australopiths
- The pitted pattern of Laetoli feet, about 3.5
mybp.
11Earliest 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)
12Earliest 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.
13Early Homo
- Homo habilis Unearthed 1960s 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 1970s Richard Leakey. Brain
size 750cc, but with more primitive looking face.
Both dated to around 2.3-2.0 mybp
14The 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
15Hand/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
16Hand/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
17Knapping apes
- Kanzi knapping studies
- Produces oldowan-like tools, but not using
percussion technique - Less power less precision and selectivity
18- 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.
19Homo 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.
20Nariokotome
- 1984 the bones of an 11 ½ year old boy were found
under a tree along a dry stream channel west of
Lake Turkana
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23Homo erectus/ergaster
- 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.
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
24A 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
25A 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 big-game
hunter.
26Homo 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.
27Summary of Hominin Species
28Acheulean 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.
29Evolving mental capacities
- Boxgrove debitage (400kybp)
- Berekhat Ram (230kybp)
- Levallois prepared core technique (300kybp
- Pigment use (300kybp)
- Control of fire (300kybp)
30Composite 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.