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Bioethics in Daily Life
Day 14
Prof. Connie J. Mulligan
Department of Anthropology
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Science and
Creationism
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What is Science?
[Empirical science] is systematic description and
classification of objects, events, [and] processes, and the
explanation of those events and processes by theories
that employ lawful regularities, all of the descriptive and
explanatory statements employed being testable against
publicly observable data.
O’Meara, 1989
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What is Science?
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Science Is…
• Empirical
• Systematic and explicit
• Theoretical, explanatory, predictive
• Self-critical, reflexive, based on testing
• Public
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What is evolution?
• From a genetic/molecular perspective, not
phenotypic
• At the most basic, causative definition
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What is evolution?
• Changes in allele frequencies over time
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What are the evolutionary forces
that can change allele
frequencies over time?
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What are the evolutionary forces
that can change allele
frequencies over time?
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Mutation
Natural selection
Genetic drift
Gene flow
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What are the evolutionary forces that
can change allele frequencies over
time?
• Mutation
– Introduces a new variant, initially at very low frequency
• Natural selection
• Genetic drift
• Gene flow
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What are the evolutionary forces that
can change allele frequencies over
time?
• Mutation
– Introduces a new variant, initially at very low frequency
• Natural selection
– Alleles that increase fitness exhibit an increase in freq
– Alleles that decrease fitness exhibit a decrease in freq
– Balancing selection/heterozygote advantage = heterogzygote
has selective advantage so frequencies of both alleles are
selected to be in balance (sickle cell allele of hemoglobin
protein)
• Genetic drift
• Gene flow
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What are the evolutionary forces that
can change allele frequencies over
time?
• Mutation
– Introduces a new variant, initially at very low frequency
• Natural selection
– Alleles that increase fitness exhibit an increase in freq
– Alleles that decrease fitness exhibit a decrease in freq
– Balancing selection/heterozygote advantage = heterogzygote
has selective advantage so frequencies of both alleles are
selected to be in balance (sickle cell allele of hemoglobin
protein)
• Genetic drift
– Random change in allele frequency from generation to
generation
• Gene flow
C. Mulligan, Copyright 2011
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What are the evolutionary forces that
can change allele frequencies over
time?
• Mutation
– Introduces a new variant, initially at very low frequency
• Natural selection
– Alleles that increase fitness exhibit an increase in freq
– Alleles that decrease fitness exhibit a decrease in freq
– Balancing selection/heterozygote advantage = heterogzygote has selective
advantage so frequencies of both alleles are selected to be in balance
(sickle cell allele of hemoglobin protein)
• Genetic drift
– Random change in allele frequency from generation to generation
• Gene flow
– One individual moves into a new population and reproduces there
• New genes are introduced into a population
• Gene flow makes 2 populations more similar
• No gene flow → reproductive isolation → genetic divergence →
speciation
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What are the evolutionary forces that
can change allele frequencies over
time?
•
•
•
•
•
Mutation
Natural selection
Genetic drift
Gene flow
In reality, all 4 forces, or a subset, can act at
the same time
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Creationist Claims
• “Evolution is only a theory”
– Like gravity, existence of the solar system, what
else??
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Creationist Claims
• “Evolution is only a theory”
– Like gravity, existence of the solar system, ??/
• Actually, evolution is both a fact and a
theory
– Fact is “an observation that has been repeatedly
confirmed and for all practical purposes is
accepted as „true.‟”
– Theory is “a well-substantiated explanation of
some aspect of the natural world that can
incorporate facts, laws, inferences, and tested
hypotheses.”
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National Academy of Sciences
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Creationist Claims
• “Evolution is unscientific, because it is not
testable or falsifiable.”
– Microevolution and macroevolution
– Fossil record and macroevolutionary
hypotheses
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Definitions
• Microevolution
– Changes in allele frequencies over relatively short time
periods/small geographic ranges/small genomic ranges
– Evolution over short time periods
– Occurs in our lifetime, i.e. is observable to all of us
• Macroevolution
– Changes in allele frequencies over relatively long time
periods/large geographic ranges/large genomic ranges
– Evolution over long time periods
• Creationists have problem with macroevolution b/c they say
we can‟t directly observe macroevolution
• We can‟t do million year experiments, but we can make
testable predictions, like in geology or astronomy
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Creationist Claims
• “Living things must be products of
intelligent design, because natural selection
could not produce some complex beings.”
– Evolution of camera-type eye
– Flagellum
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Natural selection
• Mechanism for evolutionary change
favoring the survival and reproduction of
some organisms over others because of
their biological characteristics.
• Requirements:
– Variation must exist a priori in order for natural
selection to act, i.e. natural selection does not
create a variant but „favors‟ it
– Preferred variant/phenotype must act in such a
way as to influence fitness of offspring, i.e.
Alzheimer‟s will not be selected against b/c it
occurs late in life long after childbearing years
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Misconceptions of evolution and
natural selection
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Bigger is better
Newer is better
Faster is better
Natural selection always works
Evolution has a direction or goal
Natural selection always produces perfect
structures
• All structures are adaptive
• Current structure reflect initial adaptations
• Natural selection will solve every problem
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