Why I am a doubter of evolution

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Why I am a doubter of evolution

• Ralph Seelke
• David Carrolls Critical Thinking Class,
• Nov. 19, 2008

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The short version

• Evolution (mutation and selection)
• Cant
• Do
• Anything
• Interesting

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Why I am a doubter (of evolution)

• Evolution demands that ALL the diversity and
  complexity in our world is due to natural
  processes- and the primary agent is mutation and
  selection.
• Almost everything interesting requires multiple
  independent mutational events
• A problem- when multiple things ALL have to
  happen before you can get a selective advantage-
  the probabilities become vanishingly small
  (irreducible complexity)

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• We can actually test whether evolution is able to
  work, when the evolutionary task requires
  multiple independent steps.
• When you ask natural selection to actually DO
  something involving multiple events- it cant.

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Just so you know others see this as a problem..

• A very general problem inevolution how is an
  advantageous phenotype selected when it requires
  multiple mutations, none of which are
  advantageous until all are present?...this
  presents a barrier that would appear to be
  difficult when two independent random mutations
  are required to improve fitness and insuperable
  when more than two are required (emphasis added)
• Hall (1991), PNAS 88, 5882-5886

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Where Were Going

• Confessions of an experimentalist
• Why Irreducible Complexity is a problem- the
  number TWO
• What Evolution has been able to accomplish
• What it has NOT been able to accomplish
• Some conclusions

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Why Irreducible Complexity is a Problem-
Probability!!

• The main way evolution works is through random
  processes at low probability- 1 in a million is
  a common, fairly high probability that a mutation
  might occur.
• So if you need one mutation, the odds are one in
  a million if you need TWO- the odds are now one
  in a TRILLION!!!

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Long arms AND light bones!
???
Source Ronald Pine, http//home.honolulu.hawaii.e
du/pine/book1-2.html
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So- doing one thing should be easy for evolution

• Doing two or more things, when both or all have
  to occur for evolution to take place, should be
  hard
• Can we TEST this??

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• To Test Evolution You Need
• A LARGE Population
• and/or
• MANY Generations
• A Trait That Can Evolve
• !!!!BACTERIA!!!!
• (or yeasts!)

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• 4 TRILLION in a 1 Gal Milk Jug!
• Thousands of Generations in a Year!
• COMPLEX Traits!
• When they evolve, we can FIND THEM!

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Each Transfer Produces 6.6 generations of
evolution! 46 generations per week Almost 400 per
month Over 2,400 in a year 24,000 in ten years!
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We can FIND evolution BecauseWhen the microbe
EVOLVESitGROWSor GROWS BETTER in the
environment that we give it!!!!
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(No Transcript)
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MORE Evolution Before your very eyes!
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Is the Need for Two Independent Mutations REALLY
an Evolution-Stopper?Studies with the trpA Gene
of Escherichia coli
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Testing the Two Mutation Rule

• Find a well-studied gene, with known mutations
  that inactivate it.
• Introduce 1,2,3, or four inactivating mutations
• Let the gene evolve under highly selective
  conditions

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The Gene of Choice trpA
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Results So FarIf Evolution Requires Two or More
Independent MutationsNOTHING HAPPENS
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Testing Large Populations of Bacteria for
Evolution

• Weve tested at least 2 trillion cells for their
  ability to evolve, when two mutations are
  required. So far, they cant.
• When only one mutation is required, they evolve
  readily- about 1 in every 100 million cells
  evolves to be able to make its own tryptophan.

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Results of Serial Transfer

• One culture lost its trpAB genes within 275
  generations.
• Two additional cultures have been tested for
  1050 transfers, or over 7,000 generations.
• No Trp evolution observed.
• HOWEVER they do evolve

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The cultures have evolved to be able to grow
better in the tryptophan-limited medium
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The story actually gets worse

• Since beginning this project, we learned that our
  microbe with two mutations actually should have
  been able to evolve to become Trp- but it
  hasnt.
• The bacterial population heads for an
  evolutionary dead end, where it lowers its
  ability to evolve, in exchange for short-term
  gain.

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A case of evolution preventing evolution
This path NEVER happens
Selection because of fitness advantage

Mutation
M1, M2 DeadTrpA
M1, M2 Weak TrpA
Change at 1584 ALWAYS happens
M1, M2 Dead TrpA
M1, M2 Strong TrpA
M1, M2 STILL Dead TrpA
Mutation lowers trpA expression, increases
fitness
Population of fully Trp cells
Reversion of M1 no longer selective both must
now revert for a Trp cell
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Why Does Requiring Two Changes Make Such a
Difference?

• With our strain with 1 mutation, 1 in every 100
  million cells evolves to become Trp.
• You would expect 100 mutants in a billion cells-
  the contents of 1 milliliter of a bacterial
  culture
• If you need TWO mutations, you would expect one
  in every 10,000 trillion cells- these would fill
  at least 10,000 liters of liquid!
• So at this point, evolution is an observation
  without a plausible natural explanation.

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Why Not Pursue This Approach?

• Can long-term evolution demonstrate the evolution
  of difficult traits?
• Reviewer
• On this question (evolution of difficult
  traits), we certainly know that long-term
  evolution (really long-term) has created
  "difficult" (complex) traits such as
  photosynthesis, DNA replication, protein
  synthesis, cell division, nitrogen fixation,
  transformation, toxins and many more.
• Another reviewer
• What can be said if the answer is no?

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Where this is of practical importance- antibiotic
resistant bacteria

• If, in the 1940s and 50s, we had known both the
  capabilities and limitations of evolution, we
  would have only used triple antibiotic cocktails-
  and resistance would not be the problem it is
  today.

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Acknowledgements

• Merck Foundation
• UW-Superior
• A.C. Matin Lab and Stanford University
• NUMEROUS undergraduate students!
• Pravien Abeywickrema,Kayo Sakaguchi
• Robert Jennings, Ranjuna Weerasekera
• Lynn Meyer, Sarah Rahn, Stephanie Ebnet, Jason
  Uviasah, Benjamin Okemwa, Laramie Rapp, Jory
  Fleishauer