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Anthropology
Appreciating Human Diversity
Fifteenth Edition
Conrad Phillip Kottak
University of Michigan
McGraw-Hill
© 2013 McGraw-Hill Companies. All Rights Reserved.
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EVOLUTION
AND GENETICS
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EVOLUTION AND GENETICS
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Evolution
Genetics
Biochemical, or Molecular, Genetics
Population Genetics and
Mechanisms of Genetic Evolution
• The Modern Synthesis
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EVOLUTION AND GENETICS
• What is evolution, and
how does it occur?
• How does heredity work,
and how is it studied?
• What forces contribute
to genetic evolution?
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EVOLUTION
• Humans have uniquely varied ways—cultural
and biological—of adapting to environmental
stresses
• Many scholars became interested in
biological diversity and our position within the
classification of plants and animals during the
18th century
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EVOLUTION
• Creationism: biological similarities and
differences originated at the Creation
• Linnaeus (1707–1778) developed the
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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EVOLUTION
• Catastrophism: modified version of
creationism that accounts for the fossil record
by positing divinely authored worldwide
disasters that wiped out creatures
represented in the fossil record
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THEORY AND FACT
• Evolution: transformation of species;
descent with modification
• Alternative to creationism and catastrophism
• Darwin best known of evolutionists
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THEORY AND FACT
• Darwin influenced by:
• Grandfather, Erasmus Darwin, who proclaimed
a common ancestry of all animal species
• Lyell’s principle of uniformitarianism:
the present is the key to the past
• Theory of evolution
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THEORY AND FACT
• Natural selection: the process by which
nature selects the forms most suited to
survive and reproduce in a given environment
• Competition for strategic resources
• Variety within that population
• Natural selection continues today
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GENETICS
• Genetic science helps explain causes of
biological variation
• Mendelian genetics: ways in which chromosomes
transmit genes across generations
• Biochemical genetics: examines structure,
function, and changes in DNA
• Population genetics: investigates natural
selection and the causes of genetic variation,
stability, and change
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MENDEL’S EXPERIMENTS
• Austrian monk Gregor Mendel began series
of experiments that revealed basic principle
of genetics in 1856
• Studied inheritance of seven contrasting traits
in pea plants
• Heredity is determined by discrete particles
or units
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MENDEL’S EXPERIMENTS
• Concluded that a dominant form could mask
another form in hybrid individuals, without
destroying the recessive trait
• Basic genetic units Mendel described were
factors (now called genes or alleles) located on
chromosomes
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MENDEL’S EXPERIMENTS
• Chromosome: a paired length of DNA,
composed of multiple genes
• Gene: a place (locus) on a chromosome that
determines a particular trait
• Allele: a variant to a particular gene
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MENDEL’S EXPERIMENTS
• Heterozygous: dissimilar alleles of a gene in
an offspring
• Homozygous: two identical alleles of a gene
in an offspring
• Genotype: organism’s hereditary makeup
• Phenotype: evident biological traits
• Dominance produces a distinction between
genotype and phenotype
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INDEPENDENT ASSORTMENT
AND RECOMBINATION
• Independent assortment: chromosomes
are inherited independently of one another
• Recombination: new types in an offspring
on which natural selection can operate
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Figure 5.1: Mendel’s Second Set
of Experiments with Pea Plants
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Figure 5.2: Simplified Representation of a
Normal Chromosome Pair
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Figure 5.3: Punnett Squares of a
Homozygous Cross and a Heterozygous Cross
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Figure 5.4: Determinants of Phenotypes
(Blood Groups) in the ABO System
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BIOCHEMICAL, OR MOLECULAR,
GENETICS
• Mutation: changes in the DNA molecules of
which genes and chromosomes are built
• Gametes: sex cells that make new generations
BIOCHEMICAL OR MOLECULAR GENETICS
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BIOCHEMICAL, OR MOLECULAR,
GENETICS
• DNA molecule is a double helix
• RNA carries DNA’s message to cytoplasm
(outer area)
• Structure of RNA, with paired bases,
matches DNA
• DNA, with RNA’s assistance, initiates and guides
the construction of proteins necessary for bodily
growth, maintenance, and repair
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Figure 5.5: DNA Replication
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CELL DIVISION
• Mitosis: ordinary cell division; one cell splits
to form two identical cells
• Meiosis: process that produces sex cells
• Four cells produced from one
• Each cell carries half genetic material of
original cell
• Products of meiosis from one parent combine
with those from the other parent
• Chromosomes sort independently
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CROSSING OVER
• Crossing over: the process wherein
homologous chromosomes exchange
segments by breakage and recombination
• Can occur with any chromosome pair
• An important source of variety
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Figure 5.6: Crossing Over
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MUTATION
• Base substitution mutation: substitution of
one base in a triplet by another
• If mutation occurs in sex cell, new organism will
carry mutation in every cell
• Chromosomal rearrangement: pieces
of a chromosome break off and reattach
someplace else on that chromosome
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MUTATION
• Approximately three mutations will occur in
every sex cell
• Most mutations are neutral
• Evolution depends on mutations
• Mutations are major source of genetically
transmitted variety
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POPULATION GENETICS AND
MECHANISMS OF GENETIC EVOLUTION
• Population genetics studies stable and
changing populations
• Gene pool: alleles and genotypes within
breeding population
• Genetic evolution: change in allele frequency
in a breeding population
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NATURAL SELECTION
• Genotype: the genetic makeup of an
organism
• Phenotype: organism’s biological traits
• Natural selection acts only on phenotypes
• Human biology has considerable plasticity
• The environment works on a genotype to build
a phenotype
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DIRECTIONAL SELECTION
• After several generations of selection,
gene frequencies change
• Adaptive: favored by natural selection
• Directional selection continues as long as
environmental sources stay the same
• Selection operates only on traits that are present
in a population
• Humans adapt rapidly by modifying biological
responses and learned behavior
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SEXUAL SELECTION
• Selection also
operates through
competition for mates
• Sexual selection:
based on differential
success in mating;
a selection of traits
that enhances
mating success
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STABILIZING SELECTION
• Balanced polymorphism:
frequencies of two or
more alleles of a gene
remain constant from
generation to generation
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Figure 5.7:Distribution of Sickle-Cell
Allele and Falciparum Malaria in the Old World
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APPRECIATING
ANTHROPOLOGY
• Scientists linked the first European explorers
of the New World to the origin of sexually
transmitted syphilis
• Researchers examined 26 geographically
disparate strains in the family of Treponema
bacteria
• Infections in the New World have been traced
back at least 7,000 years by studying scars
on bones
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RANDOM GENETIC DRIFT
• Random genetic drift: change in allele
frequency that results from chance
• Lost alleles can reappear in gene pool only
through mutation
• Fixation—the replacement, for example, of blue
eyes by brown eyes—is more rapid in small
populations
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GENE FLOW
• 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
• Species: group of related organisms whose
members can interbreed to produce offspring that
live and reproduce
• Gene flow tends to prevent speciation:
the formation of new species
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Figure 5.8: Gene Flow between Local Populations
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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
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PUNCTUATED EQUILIBRIUM
• Punctuated equilibrium: long periods of
stasis may be interrupted by evolutionary
leaps
• Sudden environmental change offers possibility
for the pace of evolutions to speed up
• Species can survive radical environmental shifts,
but extinction is more common
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