Transcript Primate / Human Evolution (Ch 34)

NOTES:
Ch 34 Mammals &
Primate /
Human
Evolution
(34.7-34.8)
Class: MAMMALIA
● Mammals possess unique
derived characteristics:
1) Provide young with milk
(mammary glands)
2) Internal fertilization; some
embryo development
within uterus before birth
3) Hair
Class: MAMMALIA
● Mammals possess unique
derived characteristics:
4) Endothermic (high
metabolic rate)
5) Larger brain (than other
vertebrates of similar size)
6) Differentiated teeth
Mammals…
● Most mammals are EUTHERIANS (a.k.a.
“placental” mammals”)
-highly developed at birth
-most are terrestrial, but some are marine
-important grazers and browsers in terrestrial
ecosystems
● Primates have been present for
65 million years and are defined
by shared derived characteristics
shaped by natural selection for
living in trees:
● limber shoulder joints
● dexterous hands
● sensitive fingers with nails
(not claws)
● eyes close together
● excellent hand-eye coordination
● parental care with usually single
births and long nurturing
● complex social behavior
(a) New World monkey:
spider monkey
(b) Old World monkey: macaque
(a) Gibbon
(b) Orangutan
(c) Gorilla
(d) Chimpanzees
(e) Bonobos
● Most anthropologists believe that
humans and apes diverged from a
common ancestor 6-8 million years ago
Lemurs, lorises,
and bush babies
Tarsiers
ANCESTRAL
PRIMATE
Old World monkeys
Gibbons
Orangutans
Gorillas
Chimpanzees
and bonobos
Humans
60
50
20
30
40
Time (millions of years ago)
10
0
Anthropoids
New World monkeys
(d) Chimpanzees
(e) Bonobos
Derived Characters of Humans
● A number of characters distinguish humans from
other apes
-Upright posture and bipedal locomotion
-Larger brains capable of language, symbolic
thought, artistic expression, the manufacture
and use of complex tools
-Reduced jawbones and jaw muscles
-Shorter digestive tract
The Earliest Hominins
● The study of human
origins is known as
paleoanthropology
● Hominins are more
closely related to
humans than to
chimpanzees
● Paleoanthropologists
have discovered fossils
of about 20 species of
extinct hominins
Paranthropus
robustus
Homo
ergaster
0
?
Paranthropus
boisei
0.5
Homo
neanderthalensis
1.0
Australopithecus
africanus
1.5
Millions of years ago
2.0
2.5
Kenyanthropus
platyops
Australopithecus
garhi
Australo3.0 pithecus
anamensis
3.5
Homo
habilis
4.0
4.5
Australopithecus
afarensis
5.0
Ardipithecus ramidus
5.5
6.0
6.5
7.0
Homo erectus
Orrorin tugensis
Sahelanthropus
tchadensis
Homo
rudolfensis
Homo
sapiens
● Misconception: Early hominins were
chimpanzees
**Correction: Hominins and chimpanzees
shared a common ancestor
● Misconception: Human evolution is like a
ladder leading directly to Homo sapiens
**Correction: Hominin evolution included
many branches or coexisting species,
though only humans survive today
The First Humans:
Australopiths
● Australopiths are a paraphyletic assemblage of
hominins living between 4 and 2 million years ago
● Some species, such as
Australopithecus
afarensis walked
fully upright
The First Humans:
Australopiths
(a) The Laetoli footprints
(b) Artist’s reconstruction of A. afarensis
The First Humans:
● Australopithecus africanus:
– walked upright; humanlike teeth and hands
– brain was about 1/3 size of modern humans
– 4 million years ago; existed for 3 million yrs.
Chimpanzee Australopithecus africanus Homo sapiens
● Australopithecus afarensis (“Lucy”)
– upright posture
– evidence of coexistence with A. africanus for
about 1 million years
● Australopithecus anamensis: about 4 m.y.a.
● Ardipithecus ramidus: about 4.4 m.y.a.
● hominids walked upright for two million
years without a substantial increase in
brain size!
● this posture may have freed the hands
for other things such as gathering food
or caring for infants
Early Homo
● The earliest fossils placed in our genus Homo
are those of Homo habilis, ranging in age from
about 2.4 to 1.6 million years
● Stone tools have been
found with H. habilis, giving
this species its name,
which means “handy man”
Homo habilis
● enlargement of brain is evident
in fossils dating back to about
2.4 -1.6 m.y.a. (650 cc vs. 500
cc)
● simple stone tools found with
larger-brained fossils
● coexisted with A. africanus for
almost 1 million years
 (A. africanus was an
evolutionary “dead end”)
adult cranial capacity
(range in cm3)
•Chimpanzees
300-500
•Australopithecines
400-530
•early transitional
humans 500-750
•modern humans
900-2300
Early Homo
● Homo ergaster was the first fully bipedal, largebrained hominid
● The species existed between 1.9 and 1.5 million
years ago
● Homo ergaster shows a significant
decrease in sexual
dimorphism (a size
difference between
sexes) compared with
its ancestors
Homo erectus & descendants
● taller and larger brain than H. habilis
(1200 cc)
● first hominid to migrate out of Africa
● 1.8 m.y.a. to 250,000 years ago
● H. erectus remains have
been found on other
continents
● diet shifted to include a
larger portion of meat
● intelligence allowed them
to survive in colder
climates (lived in huts or
caves, built fire, wore
clothing, designed more
refined tools)
**best known descendants
of H. erectus are
Neanderthals!
-lived in Europe, Middle
East, & Asia
-they were thick-boned with
a larger brain, they
buried their dead, and
they made hunting tools
-350,000 to 28,000 years
ago
The Origin of Modern Humans
(2 theories):
1) Multiregional
Model
2) Monogenesis
Model
(“Out of Africa”
model)
1) Multiregional Model
● proposes that modern humans evolved
in parallel along the same lines in
different parts of the world
*if true, then…
● the geographic diversity of humans
originated between 1-2 m.y.a. when H.
erectus first spread from Africa to other
continents
2) Monogenesis Model
(“Out of Africa” model)
● proposes that modern humans evolved from the
H. erectus group(s) that stayed in Africa; they
then dispersed from Africa, displacing the
Neanderthals and other hominids (suggests the
Neanderthals were NOT ancestors of modern
humans since they coexisted and were probably
evolutionary dead ends)
*if true, then…
● the geographic diversity of humans developed
within the last 100,000 years
● Mitochondrial DNA (mtDNA) studies
support the monogenesis model.
Homo Sapiens
● Homo sapiens appeared in Africa by 195,000
years ago
● All living humans are descended from these
African ancestors
Homo Sapiens
Homo Sapiens
● The oldest fossils of Homo sapiens outside Africa
date back about 115,000 years and are from the
Middle East
● Humans first arrived in the New World sometime
before 15,000 years ago
● Homo sapiens
were the first group
to show evidence
of symbolic and
sophisticated
thought
Cultural
Evolution:
● the basis of culture is learning from the
experiences of earlier generations
● transmission of information is by written
and spoken language
Cultural Evolution & Learning
*Cultural learning facilitated spread of
domesticated plants and animals
 Human societies converted from hunters &
gatherers to PASTORAL (herding large
animals) and AGRICULTURAL
Human Population Growth:
Three phases:
1) Tool use: lasted about
1 million years
-POP. = 5 million ppl.
2) Domestication of plants
& animals: lasted about
8,000 years
-POP. = 500 million ppl.
Human Population Growth:
3) Industrial Revolution: started about 300
years ago
-CURRENT POP. =
7.0 billion ppl.
-EST. POP. by 2050 = 11 billion ppl.