1. Human Biology Sylvia S. Mader Michael Windelspecht
Chapter 22
Human Evolution
Lecture Outline
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2. Points to ponder What is chemical evolution?
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, embryological, biochemical, and artificial selection (breeding) evidence that supports the theory of evolution by common descent.
What are analogous and homologous? Give examples of each.

3. Points to ponder How are humans classified?
What characteristics do primates have in common?
Explain the evolution of hominids (Family Hominidae.)
Who was Lucy?
What is the most widely accepted hypothesis for the evolution of modern humans?
Compare and contrast Cro-Magnons and Neandertals.

4. Origin of life through chemical evolution
Steps of chemical evolution:
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

5. Origin of life through chemical evolution
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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
CO2
CO2
H2O N2 N2
H2O
CO2 N2
CO2
CO2
b. The availability of energy from volcanic eruption
and lightning allowed gases to form small organic
molecules, such as nucleotides and amino acids.
CO2 N2 H2 N2 N2
fatty acids
H2O
purines
nucleotides H2
glucose
pyrimidines
amino acids N2
CO2
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.
CO2
H2O H2 N2 N2
H2O
H2O
glucose
nucleic acids proteins
CO2
nucleotides
protocells N2
amino acids
H2O
H2O

6. 22.2 Biological evolution
Biological evolution
Biological evolution – change in population or species over time
2 important points:
Living things descended from a common ancestor and thus have common chemistry
Livings things adapt to their environment
Adaptation – a characteristic that makes an organism to survive and reproduce in its environment

7. Evidence to support the theory of evolution by common descent
22.2 Biological evolution
Evidence to support the theory of evolution by common descent
Fossils in the fossil record
Biogeographical evidence
Anatomical evidence
Biochemical evidence

8. 1. What are fossils? Fossils are the traces of past life
22.2 Biological evolution
1. What are fossils?
Fossils are the traces of past life
Fossils allow us to trace the descent of a particular group
Charles Darwin, an English naturalist, relied on fossils to formulate the theory of evolution
Transitional fossils have characteristics of two different groups

9. What have we learned from the fossil record?
22.2 Biological evolution
What have we learned from the fossil record?
Fossil record tells us that life progressed from simple to more complex
Prokaryotes are the first life forms seen in the fossil record followed by unicellular eukaryotes and then multicellular eukaryotes
Fishes evolved before terrestrial plants and animals
Nonflowering plants preceded flowering plants
Amphibians preceded reptiles
Dinosaurs are directly linked to birds

10. Fossils 22.2 Biological evolution
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Present
10 MYA
feathers
wing
Moderntoothed whales
20 MYA
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.
head
wing
30 MYA
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).
claws
50 MYA
tail
feet
reptile characteristics
60 MYA
Archaeopteryx fossil
artist depiction of Archaeopteryx
bird characteristics
Hypothetical
mesonychid
skeleton
(fossil, left): © Jean-Claude Carton/Bruce Coleman/PhotoShot; (drawing, right): © Joe Tucciarone

11. 2. Biogeographical evidence
22.2 Biological evolution
2. Biogeographical evidence
Is the study of the distribution of plants and animals throughout the world
Supports the hypothesis that organisms originate in one locale and then may spread out
Different life forms are expected whenever geography separates them
Islands demonstrate this because they have many unique life forms because of geographic isolation

12. Patagonian hare and European rabbit
22.2 Biological evolution
Patagonian hare and European rabbit

13. 22.2 Biological evolution
3. Anatomical evidence
Common descent hypothesis offers plausible explanation for anatomical similarities among living organisms
Homologous structures – structures anatomically similar that are inherited by a common ancestor
e.g., Vertebrate forelimbs
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
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

14. An example of homologous structures
22.2 Biological evolution
An example of homologous structures
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bird
humerous
ulna
radius
metacarpals
phalanges
bat
whale
cat
horse
human

15. Homologous structures in vertebrate embryos
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

16. 22.2 Biological evolution
4. Biochemical evidence
Almost all living things use the same biochemicals (e.g., DNA and ATP)
Living things use the same triplet code
Living things use the same 20 amino acids in their proteins
Living things share many of the same genes

17. Biochemical evidence describes evolutionary relationships
22.2 Biological evolution
Biochemical evidence describes evolutionary relationships
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Species
Number of Amino Acid Differences Compared to
Human Cytochrome c
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

18. 22.2 Biological evolution
Natural selection
A theory by Darwin that describes a mechanism by which a species becomes adapted to its environment
3 vital elements:
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

19. Natural selection 22.2 Biological evolution Lamarck’s proposal
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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.

20. The arrival of humans on earth
22.3 Classification of humans
The arrival of humans on earth

21. Three domains of life 22.3 Classification of humans fungi plants
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fungi
plants
animals
EUKARYA
protists
protists
heterotrophic
bacteria
cyanobacteria
ARCHAEA
BACTERIA
common ancestor

22. Primates Characteristics: Two suborders: Opposable thumb
22.3 Classification of humans
Primates
Characteristics:
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:
Prosimians – includes lemurs, tarsiers, and lorises
Anthropoids – includes monkeys, apes, and humans

23. Evolution of primates
22.4 Evolution of hominids

24. Evolution of primates 22.4 Evolution of hominids
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Humans
hominin
Chimpanzees
Hominines
common
chimpanzee
Hominids
Gorillas
Hominoids
western
lowland
gorilla
Orangutans
Prosimians Anthropoids
Bornean
orangutan
Gibbons
white-handed
gibbon
rhesus
monkey
Old World Monkeys
New World Monkeys
Mammalian
ancestor
enters trees.
capuchin
monkey
Tarsiers
Philippine
tarsier
ring-tailed
lemur
Prosimians Anthropoids
Lemurs 70 60 50 40 30 20 10
Million years Ago (MYA)
PRESENT

25. Comparing the human skeleton to the chimpanzee
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.

26. 22.4 Evolution of hominins
Evolution of hominins
Hominids – All species of the genus Homo and their close relatives
Characteristics:
Bipedal
Flatter face with more pronounced chin
Smaller face
Brain size
Hominins split from the ape line of descent 7 MYA

27. 22.4 Evolution of hominids
Australopithecines
A group of hominins that evolved and diversified in Africa 3 MYA
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
Famous skeleton named “Lucy” is from this group
Australopithicus afarensis
Australopithecus africanus has a large brain is the most likely ancestral candidate for early Homo

28. 22.4 Evolution of hominids
Australopithecines

29. Characteristics of Homo
22.5 Evolution of humans
Characteristics of Homo
Brain size is 600 cm3 or greater
Evidence of tool use
Jaw and teeth resemble humans
Early Homo representatives:
Homo habilis
Homo erectus
Later Homo representatives:
Neandertals
Cro-Magnons

30. Human evolution 22.5 Evolution of humans Sahelanthropus tchadensis
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Sahelanthropus
tchadensis
Australopithecus
afarensis
Paranthropus
robustus
Homo habilis
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
Ardipithicus ramidus
Paranthropus boisei
Sahelanthropus tchadensis
Paranthropus robustus
7.5 7
6.5 6
5.5 5
4.5 4
3.5 3
2.5 2
1.5 1
0.5
Million Years Ago (MYA)

31. Early Homo: Homo habilis
22.5 Evolution of humans
Early Homo: Homo habilis
Lived MYA
Large brain with enlarged speech area
Omnivorous (hunters and gatherers)
Primitive tools
Culture may have existed

32. Early Homo: Homo erectus
22.5 Evolution of humans
Early Homo: Homo erectus
Lived 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

33. © National Museum of Kenya
22.5 Evolution of humans
Later Homo individual
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neck of femur
femur
© National Museum of Kenya

34. Modern Humans: Homo sapiens
22.5 Evolution of humans
Modern Humans: Homo sapiens
2 hypotheses:
Multiregional continuity – suggests that modern humans evolved from H. erectus in several geographic places
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)

35. Homo ergaster evolves into modern humans in Asia, Africa, and Europe.
22.5 Evolution of humans
Hypotheses for modern human evolution
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ASIA
AFRICA
EUROPE
ASIA
AFRICA
EUROPE
0.1
0.1
Homo sapiens
Homo sapiens
Homo sapiens
Homo sapiens
Homo sapiens
Homo sapiens
Homo ergaster evolves into modern humans
in Asia, Africa, and Europe.
Homo sapiens
interbreeding 1 1
Modern humans evolve
in Africa and migrate
to Asia and Europe.
Millions of Years Ago (MYA)
Millions of Years Ago (MYA)
interbreeding
migration of
Homo ergaster
migration of
Homo ergaster
migration of
Homo ergaster
migration of
Homo ergaster 2 2
Homo ergaster
Homo ergaster
a. Multiregional continuity
b. Out of Africa

36. Neandertals Discovered in Germany 2000 years ago Massive brow ridges
22.5 Evolution of humans
Neandertals
Discovered in Germany 2000 years ago
Massive brow ridges
Nose, jaws and teeth protrude forward
Low and sloping forehead, no chin

37. Cro-Magnons Lived about 40,000 to 10,000 years ago
22.5 Evolution of humans
Cro-Magnons
Lived about 40,000 to 10,000 years ago
Oldest fossils to be designated Homo sapiens
Modern appearance
Advanced culture including art, tool and maybe language
Good cooperative hunters

38. 22.5 Evolution of humans
Human variation
Human variations between populations are called ethnicities
Variations evolved as adaptation to local environments:
Skin color: range of dark to light
Body shape: Bergmann’s rule and Allen’s rule

39. 22.5 Evolution of humans
Human variation