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1
Evolution
Anthropology:
The Exploration of Human Diversity
11th Edition
Conrad Phillip Kottak
McGraw-Hill
© 2005 The McGraw-Hill Companies, Inc.
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Evolution
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Evolution
Genetics
Mendel’s Experiments
Biochemical, or Molecular, Genetics
Population Genetics and Mechanisms
of Genetic Evolution
• Natural Selection
McGraw-Hill
© 2005 The McGraw-Hill Companies, Inc.
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Evolution
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McGraw-Hill
Polymorphisms
Understanding Ourselves
Mutations and Variety
Random Genetic Drift
Gene Flow
The Modern Synthesis
© 2005 The McGraw-Hill Companies, Inc.
4
Evolution
• Humans have uniquely varied ways—
cultural and biological—of evolving, of
adapting to environmental stresses
• Many scholars became interested in
biological diversity and our position
within the classification of plants and
animals during 18th century
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5
Evolution
• Creationism—biological similarities and
differences originated at the Creation
• Linnaeus (1707-1778) developed first
comprehensive and still influential
classification, or taxonomy, of plants
and animals
Fossil discoveries during the 18th and 19th
centuries raised doubts about creationism
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6
Evolution
• Catastrophism—modified version of
Creationism accounts for the fossil
record by positing divinely authored
worldwide disasters that wiped out
creatures represented in the fossil
record
The alternative to creationism and
catastrophism was transformism, also
called evolution
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Evolution
• Darwin influenced Lyell’s Principle of
Uniformitarianism—explanations for
past events should be sought in the
long-term action of ordinary forces that
still work today
• Natural Selection—process by which
nature selects the forms most suited to
survive and reproduce in a given
environment
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Evolution
• For natural selection to work on a given
population, there must be:
– Variety within that population
– Competition for strategic resources
Process of natural selection continues as
long as the relationship between the
population and its environment remains the
same
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9
Genetics
• Genetic science emerged after Darwin
– Mendelian Genetics—studies ways in
which chromosomes transmit genes across
generations
– Population Genetics—investigates
natural selection and other causes of
genetic variation, stability, and change in
breeding populations
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10
Mendel’s Experiments
• Austrian monk Gregor Mendel began a
series of experiments that revealed
basic principle of genetics in 1856
– Studied inheritance of seven contrasting
traits in pea plants
– Discovered heredity is determined by
discrete particles or units
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Mendel’s Experiments
– Concluded that although a dominant form
could mask the other form in hybrid, or
mixed, individuals, the dominated trait—the
recessive—was not destroyed
– Basic genetic units Mendel described were
factors (now called genes or alleles)
located on chromosomes
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Mendel’s Experiments
– Alleles—biochemically different forms of a
given gene
• Heterozygous—dissimilar alleles of a gene in
an offspring
• Homozygous—two identical alleles of a gene
in an offspring
• Dominance produces a distinction between
genotype—hereditary makeup and
phenotype—expressed physical
characteristics
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13
Mendel’s Experiments
• Independent Assortment and
Recombination
– Independent Assortment—Mendel’s
discovery that traits are inherited
independently of one another
– Recombination—combination of genetic
traits in an offspring; creates new types on
which natural selection can operate
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Mendel’s Experiments
• Mendel’s Second Set of Experiments
with Pea Plants
– Insert Figure 4.1
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Mendel’s Experiments
• Simplified Representation of a Normal
Chromosome Pair
– Insert Figure 4.2
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Mendel’s Experiments
• Punnett Squares of a Homozygous
Cross and a Heterozygous Cross
– Insert Figure 4.3
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Mendel’s Experiments
• Determinants of Phenotypes (Blood
Groups) in the ABO System
– Insert Figure 4.4
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Biochemical, or Molecular,
Genetics
• Studies structure, function, and changes
in genetic material
– Mutations—changes in the DNA
molecules of which genes and
chromosomes are built
– Gametes—sex cells that make new
generations
McGraw-Hill
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Biochemical, or Molecular,
Genetics
• DNA molecule is a double helix
– RNA carries DNA’s message to its
cytoplasm (outer area)
– Structure of RNA, with paired bases,
matches DNA
DNA, with RNA’s assistance, initiates and
guides the construction of hundreds of
proteins necessary for bodily growth,
maintenance, and repair
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20
Biochemical, or Molecular,
Genetics
• A Double-Stranded DNA Molecule
– Insert Figure 4.5
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21
Biochemical, or Molecular,
Genetics
• Crossing Over
– Insert Figure 4.6
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Biochemical, or Molecular,
Genetics
• Cell Division
– Mitosis—ordinary cell division, wherein
one cell splits to form two identical cells
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Biochemical, or Molecular,
Genetics
• Cell Division
– Meiosis—special process by which sex
cells are produced
• 4 cells produced from • Fertilization allows the
one
products of meiosis from
• Each cell carries half
one parent to recombine
the genetic material of
with those from the
the original cell (i.e.,
other parent
twenty-three
chromosomes instead • Chromosomes sort
independently
of forty-six)
McGraw-Hill
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Biochemical, or Molecular,
Genetics
• Crossing Over
– Process where homologous chromosomes
exchange segments by breakage and
recombination
Independent assortment of chromosomes
permits parents’ genotypes to be assorted
in more than 8 million different ways
McGraw-Hill
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25
Population Genetics and
Mechanisms of Genetic Evolution
• Population genetics studies stable and
changing populations in which most
breeding normally takes place
– Gene Pool—refers to alleles and
genotypes within breeding population
McGraw-Hill
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Population Genetics and
Mechanisms of Genetic Evolution
– Genetic Evolution—change in the
frequency of alleles in breeding population
from generation to generation
• Any factor that contributes to a change
considered mechanism of genetic evolution
Natural selection
Genetic drift
McGraw-Hill
Mutation
Gene flow
© 2005 The McGraw-Hill Companies, Inc.
27
Natural Selection
• Genotype refers to the genetic makeup
of an organism
• Phenotype is the organism’s evident
biological characteristics
– Natural selection only act on phenotypes
– Environmental influence in this interaction
extremely important
– Lends great plasticity to human biology
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Natural Selection
• Directional Selection
– After several generations of selection,
gene frequencies change
• Natural selection will have occurred
• Adaptive—favored by natural selection
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Natural Selection
• Directional Selection
– Directional selection—long-term
selection of the same trait(s)
• Directional selection continues as long as
environmental forces stay the same
– Sexual selection—certain traits of one sex
selected because of advantages they
confer in winning mates
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30
Polymorphisms
• Balanced polymorphism—frequencies
of two or more alleles of a gene remain
constant from generation to generation
Sickle-Cell Anemia
• HbA and HbS alleles largely determines hemoglobin
production in humans
• Homozygous HbA produces normal hemoglobin
• Homozygous HbS produces lethal sickle-cell anemia
• Heterozygosity for this gene produces (in some
circumstances) deleterious but nonlethal sickle-cell
syndrome
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31
Polymorphisms
– HbS existed at surprisingly high
frequencies in certain populations in Africa,
India, and the Mediterranean
• Heterozygous form produced phenotype
resistant to malaria
– Demonstrates relativity of evolution
through national selection
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Polymorphisms
• Distribution of Sickle-Cell Allele and
Falciparum Malaria in the Old World
– Insert Figure 4.7
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33
Understanding Ourselves
• Human biology is plastic, but only to a
degree
• Plasticity through culture steps in to
complement human biological plasticity
McGraw-Hill
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34
Mutations and Variety
• Mutation major source of genetically
transmitted variety
• Variants produced through mutation can
be especially significant if there is
change in selective forces
McGraw-Hill
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35
Random Genetic Drift
• Random genetic drift—loss of alleles
from a population’s gene pool through
chance
Lost alleles reappear in gene pool only
through mutation
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36
Gene Flow
• Exchange of genetic material between
populations of the same species
Alleles spread through gene flow even
when selection not operating on the allele
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37
Gene Flow
• Important in study of origin of species
– Species—group of related organisms
whose members can interbreed to produce
offspring that live and reproduce
– Gene flow tends to prevent speciation—
formation of new species
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Gene Flow
• Gene Flow between Local Population
– Insert Figure 4.8
McGraw-Hill
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The Modern Synthesis
• Currently accepted view of evolution
– Microevolution—small-scale changes in
allele frequencies over just a few
generations
– Macroevolution—large-scale changes in
allele frequencies in a population over a
longer time period
Microevolution and macroevolution happen
in the same way and for the same reasons
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40
The Modern Synthesis
• Gradual or Rapid Change
– Darwin: minor alterations in gene pool,
accumulating generation after generation,
added up to major changes
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41
The Modern Synthesis
• Gradual or Rapid Change
– Punctuated equilibrium—long periods of
stasis, during which species change little,
interrupted by evolutionary leaps
Sudden environmental change, rather than
Species
radical environmental
extinctioncan
andsurvive
replacement,
presents
shifts,
but more
common
fate isto
extinction
possibility
for pace
of evolution
speed up
McGraw-Hill
© 2005 The McGraw-Hill Companies, Inc.