HOMINID EVOLUTION
In a nutshell
The Stage:
The Great Rift Valley
K-Ar Dating
Dates new rock formation
lavas, tufts, pumice
Potassium (K) - great abundance in earth’s crust
K-39 93.2%
K-41 6.8%
K-40 0.0118% (radioactive)
K-40 decays to Ca-40 (89%) and Ar-40 (11%)
long half-life, 1.3 billion years
Ar-40 – inactive gas, diffusion during rock form.
Ratio of K-40 to Ar-40 denotes the moment of
rock formation
Lines of Evidence
Fossils
DNA
DNA
Nuclear DNA
mtDNA
Y Chromosome
Fossils
Pongids and Hominids
Pongidae (pongids)
Modern pongids include:
Gorillas (Gorilla gorilla)
Common chimpanzee (Pan troglodytes)
Bonobo chimpanzee (Pan paniscus)
Orangutan (Pongo pygmaeus)
Hominidae (hominids)
Modern hominids are represented
by a single species:
Homo sapiens sapiens
Pongid/Hominid Split:
The Fossil Perspective
There are no fossil remains of pongids
or hominids between 15-6mya.
Paleontologists theorize that the
hominid lineage evolved from the
pongid lineage 15-17 mya. This
would provide hominids enough time
to evolve from the pongids observed
at 17 mya:
Ramapithecus, Sivapithcus,
Gigantopithecus, Proconsul,
Dryopithecus
Pongid/Hominid Split:
The Fossil Perspective
Possible Hominid Ancestors:
Ramapithecus
Gigantopithecus
Proconsul
Sivapithecus
Dryopithecus
Physical Characteristics:
large-bodied, typical primate
characteristics, not well
understood
Pongid/Hominid Split
DNA Perspective
Nuclear and mtDNA
evidence from modern
humans and pongids
indicates that they are
very similar genetically
– chimps are 99% the
same as humans
Therefore, not much
time is needed for the
hominids to evolve
from the pongids –
estimate is 6-7 mya
First Hominids
Ardipithecus
Maeve Leakey
Lake Turkana
4-6 mya
Pongid Physical
Characteristics:
small brained
curved phalanges
prognathic
large canines
divergent toe
Bipedal
pelvis, femur, foot
Australopithecines
Australopithecus afarensis; 3-4 mya
cranial capacity 450-530cc,
“Lucy”, bipedal,
primitive condition
Robust lineage
Gracile lineage
Robust Australopithecines
Australopithecus robustus
A. boisei (Zinjanthropus)
A. aethiopicus
(The Black Skull)
1.8-3mya
Sagittal crest
Large brow ridge
Huge cheeks
Prognathic
Large molars/small incissors
(herbivorous)
Cranial capacity 500-700cc
Gracile Australopithecines
Australopithecus africanus
1.5-3mya
No saggital crest
Small, dish-shaped face
Small molars/larger incissors
(omnivorous)
Cranial Capacity 500-750 cc
Early Homo Lineage
Homo habilis
Homo rudolfensis
Homo ergaster
1.8-1mya
Evolved from
Australopithecus africanus
What makes this species
Homo and not
Australopithecus?
Cranial Capacity
750-850cc
Tools: Oldowan
Homo erectus
1.5-.3mya
Large brained
(1000-1250 cc)
Out of Africa
Fire
Tools: Acheulian
Homo sapiens
“Archaic” Homo sapiens
400,000-100,000 ya
Modern Homo sapiens sapiens
150,000-present
Neanderthals, 120,000-32,000ya
Homo neanderthalensis?
OR
Homo sapiens neanderthalensis
Neanderthals
Europe and
Middle East
Large boned
Large face
Large brow ridge
Large molars
Large nasal cavity
Occipital bun
Mousterian tool tradition
Modern Homo sapiens
Diverse Paleolithic Tool
Tradition
Fossil Evidence
Different Species
Multiregional Hypothesis
DNA Evidence
mtDNA
Y Chromosome
Fossil Evidence
Modern Homo sapiens
Separate Species: H. sapiens evolved from
H. erectus 400-500,000ya
H. habilis
H. erectus
Multiregional
Hypothesis
Homo sapiens
H. sapiens neanderthalensis
H. sapiens
DNA Evidence
Modern Homo sapiens
mtDNA, modern populations
120,000 years ago out of Africa
Y Chromosome, modern populations
Two lines of migration out of Africa:
50,000 and 40,000 BP
Neanderthals,
mtDNA of fossils
Not in direct lineage
with humans
Hominid Evolution:
The Simplified Version
Chimpanzees, Gorillas, Orangs
100,000 ya
H. sapiens
H. neanderthalensis?
H. erectus
1mya
Homo habilis
A. robustus
A. boisei
3mya
A. aethiopicus
Australopithecus afarensis
5mya
Ardipithecus sp.
7mya
10-15mya
A. africanus
Pongidae
Hominidae