Download chapt22_lecture Human Origins

Human Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 22
Human
Evolution
Lecture Outline
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Points to Ponder
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What is the chemical evolution of life?
What is biological evolution?
What is natural selection and what three elements are vital for this?
What was Darwin’s contribution to evolution?
What have we learned from the fossil record?
Explain the fossil, biogeographical, anatomical, and biochemical
evidence that supports the theory of evolution by common descent?
What are analogous, homologous and vestigial structures? Give
examples of each.
How are humans classified?
What characteristics do primates have in common?
Explain the evolution of hominids.
Who is Lucy?
Explain the evolution of humans.
What are the 2 hypotheses for modern man?
Compare and contrast Cro-Magnons and Neandertals
22.1 Origin of life
Origin of life through chemical evolution
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Steps of chemical evolution:
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Gases of the primitive atmosphere formed small
organic molecules
Molecules combined to form macromolecules
Only RNA might have been needed to form the first
cells and is supported by the fact that RNA can act
as enzymes called ribozymes (RNA-first hypothesis)
Protocells made of proteins and lipids could
metabolize by using oceanic organic molecules but
could not reproduce
The true cell can reproduce and has DNA as its
genetic material
22.1 Origin of life
Origin of life through chemical evolution
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H2
CO2
CO2
N2
H2O
N2
a. The primitive atmosphere contained gases,
including H2O, CO2, and N2, that escaped from
volcanoes. As the water vapor cooled, some
gases were washed into the oceans by rain.
CO2
H2O
CO2
CO2
N2
CO2
CO2
H2
N2
fatty acids
N2
N2
H2O
purines
nucleotides
glucose
pyrimidines
CO2
H2O
H2O
CO2
N2
H2O
N2
glucose
nucleic acids proteins
CO2
protocells
H2O
H2
amino acids
N2
H2
b. The availability of energy from volcanic eruption
and lightning allowed gases to form small organic
molecules, such as nucleotides and amino acids.
N2
nucleotides
amino acids
H2O
c. Small organic molecules could have joined to
form proteins and nucleic acids, which became
incorporated into membrane-bound spheres. The
spheres became the first cells, called protocells.
Later protocells became true cells that could
reproduce.
22.2 Biological evolution
Biological evolution
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Biological evolution – change in population or
species over time
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2 important points:
1. Living things descended from a common ancestor
and thus have common chemistry
2. Livings things adapt to their environment
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Adaptation – a characteristic that makes an
organism to survive and reproduce in its
environment
22.2 Biological evolution
Evidence to support the theory of
evolution by common descent
1.
2.
3.
4.
Fossils in the fossil record
Biogeographical evidence
Anatomical evidence
Biochemical evidence
22.2 Biological evolution
1. What are fossils?
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Fossils are the traces of past life
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Fossils allow us to trace the descent of a
particular group
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Charles Darwin, an English naturalist, relied on
fossils to formulate the theory of evolution
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Transitional fossils have characteristics of two
different groups
22.2 Biological evolution
What have we learned from the
fossil record?
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Fossil record tells us that life progressed from simple to more
complex
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Prokaryotes are the first life forms seen in the fossil record
followed by unicellular eukaryotes and then multicellular
eukaryotes
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Fishes evolved before terrestrial plants and animals
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Nonflowering plants preceded flowering plants
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Amphibians preceded reptiles
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Dinosaurs are directly linked to birds
22.2 Biological evolution
Fossils
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Present
10 MYA
feathers
Moderntoothed whales
wing
20 MYA
head
30 MYA
wing
Rodhocetus kasrani’s
reduced hind limbs could not have
aided it in walking or swimming.
Rodhocetus swam with an up-and-down
motion, as do modern whales.
40 MYA
teeth
tail with vertebrae
Ambulocetus natans
probably walked on land (as do
modern sea lions) and swam by
flexing its backbone and paddling with
its hind limbs (as do modern otters).
50 MYA
claws
feet
tail
reptile characteristics
60 MYA
Archaeopteryx fossil
artist depiction of Archaeopteryx
(fossil, left): © Jean-Claude Carton/Bruce Coleman/PhotoShot; (drawing, right): © Joe Tucciarone
bird characteristics
Hypothetical
mesonychid
skeleton
22.2 Biological evolution
2. Biogeographical evidence
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Is the study of the distribution of plants and animals
throughout the world
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Supports the hypothesis that organisms originate in
one locale and then may spread out
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Different life forms are expected whenever geography
separates them
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Islands demonstrate this because they have many
unique life forms because of geographic isolation
22.2 Biological evolution
Patagonian hare and
European rabbit
22.2 Biological evolution
3. Anatomical evidence
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Common descent hypothesis offers plausible explanation for
anatomical similarities among living organisms
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Homologous structures – structures anatomically similar that are
inherited by a common ancestor
e.g., Vertebrate forelimbs
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Analogous structures – structures that serve the same function but
they do not share a common ancestry and thus are not
constructed the same
e.g., Wings of a bird and wings of an insect
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Vestigial structures – anatomical features fully developed in one
group but are reduced and may have no function in another group
e.g., Whales have a vestigial pelvic girdle and legs
22.2 Biological evolution
An example of homologous structures
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bird
humerous
ulna
radius
metacarpals
phalanges
bat
whale
cat
horse
human
22.2 Biological evolution
Homologous structures in
vertebrate embryos
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Pig embryo
pharyngeal
pouches
postanal
tail
Chick embryo
(both): © Carolina Biological Supply/Phototake
22.2 Biological evolution
4. Biochemical evidence
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Almost all living things use the same
biochemicals (e.g., DNA and ATP)
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Living things use the same triplet code
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Living things use the same 20 amino acids in
their proteins
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Living things share many of the same genes
22.2 Biological evolution
Biochemical evidence describes
evolutionary relationships
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Species
Number of Amino Acid Differences Compared to
Human Cytochrome c
0
human
Cytochrome c is a small protein
that plays an important role in
the electron transport chain
within mitochondria of all cells.
2
monkey
9
pig
11
duck
18
turtle
20
fish
30
moth
51
yeast
22.2 Biological evolution
Natural selection
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A theory by Darwin that describes a
mechanism by which a species becomes
adapted to its environment
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3 vital elements:
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Variation – there must be physical variations that
can be passed from generation to generation
Competition – there must be competition for limited
resources (food, mates, shelter) and those better
adapted will survive and reproduce
Adaptation – subsequent generations will see an
increase in individuals with the same adaptations as
long as the environment remains unchanged
22.2 Biological evolution
Natural selection
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Lamarck’s proposal
Darwin’s proposal
Originally, giraffes had
short necks.
Originally, giraffe neck
length varied.
Giraffes stretched their necks
in order to reach food.
Competition for resources
causes long-necked giraffes
to have the most offspring.
With continual stretching, most
giraffes now have long necks.
Due to natural selection, most
giraffes now have long necks.
22.3 Classification of humans
The arrival of humans on earth
22.3 Classification of humans
Three domains of life
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fungi
plants
animals
EUKARYA
protists
heterotrophic
bacteria
protists
cyanobacteria
ARCHAEA
BACTERIA
common ancestor
22.3 Classification of humans
Primates
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Characteristics:
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Opposable thumb
Stereoscopic vision (depth perception)
Well-developed brain
Reduced # of offspring (usually a single birth) with
an increased period of parental care
Emphasis on learned behavior and social
interactions
Two suborders:
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Prosimians – includes lemurs, tarsiers, and lorises
Anthropoids – includes monkeys, apes, and humans
22.3 Classification of humans
Comparing the human skeleton to the
chimpanzee
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Human spine exits from the skull’s center;
ape spine exits from rear of skull.
Human spine is S-shaped; ape spine has a
slight curve.
Human pelvis is bowl-shaped; ape pelvis is
longer and more narrow.
Human femurs angle inward to the knees;
ape femurs angle out a bit.
Human knee can support more weight than
ape knee.
Human foot has an arch; ape foot has
no arch.
a.
b.
22.4 Evolution of hominids
Evolution of primates
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Humans
Hominines
Hominids
Hominoids
Prosimians Anthropoids
hominin
Chimpanzees
common
chimpanzee
Gorillas
western
lowland
gorilla
Orangutans
Bornean
orangutan
Gibbons
white-handed
gibbon
rhesus
monkey
Old World Monkeys
Mammalian
ancestor
enters trees.
capuchin
monkey
Tarsiers
Philippine
tarsier
ring-tailed
lemur
Lemurs
70
60
50
40
30
20
Million years Ago (MYA)
10
PRESENT
Prosimians Anthropoids
New World Monkeys
22.4 Evolution of hominins
Evolution of hominins
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Hominids – All species of the genus Homo and their
close relatives
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Characteristics:
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Bipedal
Flatter face with more pronounced chin
Brain size
Suggested fossils of the first hominins (6-7 MYA):
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Central African fossil 7 MYA (Sahelanthropus tchadensis)
Eastern African fossil 6 MYA (Orrorin tugenensis)
Eastern African fossil 5.8-5.2 MYA (Ardipithecus kadabba)
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Hominins split from the ape line of descent 7 MYA
22.4 Evolution of hominids
Australopithecines
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A group of hominins that evolved and diversified in
Africa 3 MYA
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Some had slight frames and others were robust with massive
jaws that fed on plant materials
Walked upright
Limbs proportions are ape-like
Small brain
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Famous skeleton named “Lucy” is from this group
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Australopithecus africanus has a large brain is the most
likely ancestral candidate for early Homo
22.4 Evolution of hominids
Australopithecines
22.5 Evolution of humans
Characteristics of Homo
1. Brain size is 600 cm3 or greater
2. Evidence of tool use
3. Jaw and teeth resemble humans
Early Homo representatives:
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Homo habilis
Homo erectus
Later Homo representatives:
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Neandertals
Cro-Magnons
22.5 Evolution of humans
Human evolution
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Sahelanthropus
tchadensis
Australopithecus
afarensis
Homo habilis
Paranthropus
robustus
Homo sapiens
Homo sapiens
Homo neandertalensis
Homo heidelbergensis
Homo erectus
Homo ergaster
Homo rudolfensis
Australopithecus garhi
Homo habilis
Australopithecus africanus
Australopithecus afarensis
Australopithecus anamensis
Paranthropus aethiopicus
Paranthropus boisei
Ardipithicus ramidus
Paranthropus robustus
Sahelanthropus tchadensis
7.5
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6.5
6
5.5
5
4.5
4
3.5
Million Years Ago
(MYA)
3
2.5
2
1.5
1
0.5
0
22.5 Evolution of humans
Early Homo: Homo habilis
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Lived 2.0-1.9 MYA
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Large brain with enlarged speech area
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Omnivorous (hunters and gatherers)
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Primitive tools
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Culture may have existed
22.5 Evolution of humans
Early Homo: Homo erectus
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Lived 1.9-0.3 MYA
Larger brain than H. habilis
Flat face with the nose projected
Tall and stood erect
Striding gait
May have migrated from Africa to Europe and
Asia
Advanced tools and fire (systematic hunters)
Language may have evolved
22.5 Evolution of humans
Later Homo individual
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neck of femur
femur
© National Museum of Kenya
22.5 Evolution of humans
Modern Humans: Homo sapiens
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2 hypotheses:
1. Multiregional continuity – suggests that
modern humans evolved from H. erectus in
several geographic places
2. Out-of-Africa hypothesis – modern humans
evolved from H. erectus most likely only in
Africa and later migrated to Europe and Asia
(this hypothesis has the most support)
22.5 Evolution of humans
Hypotheses for modern human evolution
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ASIA
AFRICA
EUROPE
ASIA
0.1
AFRICA
EUROPE
Homo sapiens
Homo sapiens
0.1
Homo sapiens
Homo sapiens
Homo sapiens
Homo sapiens
interbreeding
1
interbreeding
2
migration of
Homo ergaster
migration of
Homo ergaster
Millions of Years Ago (MYA)
Millions of Years Ago (MYA)
Homo ergaster evolves into modern humans
in Asia, Africa, and Europe.
Homo sapiens
1
2
migration of
Homo ergaster
migration of
Homo ergaster
Homo ergaster
Homo ergaster
a. Multiregional continuity
Modern humans evolve
in Africa and migrate
to Asia and Europe.
b. Out of Africa
22.5 Evolution of humans
Neandertals
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Discovered in
Germany 2000
years ago
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Massive brow ridges
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Nose, jaws and
teeth protrude
forward
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Low and sloping
forehead, no chin
22.5 Evolution of humans
Cro-Magnons
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Lived about 40,000 to
10,000 years ago
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Oldest fossils to be
designated Homo
sapiens
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Modern appearance
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Advanced culture
including art, tool and
maybe language
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Good cooperative
hunters
22.5 Evolution of humans
Human variation
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Human variations between populations
are called ethnicities
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Variations evolved as adaptation to local
environments:
– Skin color: range of dark to light
– Body shape: Bergmann’s rule and Allen’s
rule
22.5 Evolution of humans
Human variation