Transcript Specific Points `Bout Evolution

Specific Points ‘Bout Evolution
• Each incremental step on the way towards the design of
every complex structure must confer more advantage than the
previous step along the way
• The Blind Watchmaker: Evolution has no plan or goal it is controlled entirely by competition and is short-sighted
Each step along the way…
(micro- vs. macro-evolution)
• “If it could be demonstrated that any complex
organ [or structure] existed which could not
possibly have been formed by numerous,
successive, slight modifications, my theory would
absolutely break down.” - Chuck
• Evolution by natural selection can easily explain
slight changes in already existing complex
structures, but what about their inception?
• First some easier structures, then some tough
ones...
Flippers of Mammals
• Even in human populations
there is variation in the amount
of skin between digits of the
hands and feet, often known a
“webbed feet”
• This same variation could have
existed in the sea mammal
ancestor. If they were
beginning to exploit the sea
niche, more webbing would be
more beneficial
• But no gill adaptation Bummer...
Flight in Mammals
• How would mammals
acquire the ability to
fly? What behavior
would it allow? What
niche could be
exploited?
• Bug eating mammals
in trees
• Gliding ---> Flying
(membranes)
Flight in Insects
• Sure, wings are highly
beneficial, but how about
all the precursors to
wings?
• Would little nubs of wings
help the “nubbed” enough
to drive evolution towards
larger nubs?
• What behavior? Which
niche?
• Water insects
One true challenge to Darwinian
Evolution: Biochemistry
• Biochemical reactions inside of cells are
extremely complex.
• If they came about through Darwinian Evolution,
each step along the way in their development must
have been “fitter” than the previous one.
• Starting from the present and working backwards,
we must be able to walk through a series of
structures each less complex and less fit than the
one closer to present day.
• For example, a music box...
The Mammalian Eye
• Argument #1: Could
all of these pieces fall
into place and interact
in such complex ways
by simple, incremental
steps?
• In other words, is this
irreducibly complex?
• A complexity quote
from the book...
The Protein Clotting Cascade
The Cilial/Flagellar Motor
Argument #2: For a structure with
a particular purpose, how could
the previous structures have
worked to generate an output that
requires such complexity to work
at all?
• Swimmer Analogy
• Any Mechanical System:
take one piece out and
the thing don’t work at all
Darwin’s Black Box Conclusions
• Assumption #1: FALSE Each piece of the
biochemical puzzle is not separate to begin with.
E.g. nerve cells, signalling cascades, etc, etc.
(music box example)
• Assumption #2: FALSE The structures and
cascades did not always necessarily serve the
purpose that they do now. Flagella, photocell,
nerve cells, etc, etc. (music box example)
• Which leads us to...
The Blind Watchmaker:
Fallacy #1 and #2 summed up
• Even though modern structures serve remarkable purposes,
they weren’t created to fulfill those roles
• Each structure in the body of any animal must have come
about by accident. If the mutation solved some problem, it
stayed and changed the gene pool, if it didn’t then it was
outcompeted in the gene pool.
• Evolution must be short-sighted. It deals only with the
baby step that occurs away from the current position.
Many of these steps can lead to complex structures that
appear to be made for a purpose, but were not.
• Some quotes...
What’s wrong with this picture?
• “Evolution’s intent for us lies far beyond exercises of
‘mind over matter’ though we need to know of such
capacities. Our job on earth is not to mutilate our earth
matrix, but to nurture and maintain her as she nurtures and
maintains us.” p. 179
• “Arthur Koestler…considered the fact that the left
hemisphere has almost no connection with the balancing
limbic system an error of evolution. I would point out it is
a gamble of evolution’s but hardly an error.” p. 240
• “What use would be… half a lung?”
A Blindness Example:
Flippers
Convergence #2: similar environments/
different parts of the world
Okay, Explain this Complex
Structure in terms of Evolution
Okay, Explain This:
Mammalian Ears
• Waves in our environment tell us much
• Strong selection
towards perception of
waves
• Any delicate surface
linked to activating a
nerve cell will do
• All the rest are
structural details
Cilia in the Cochlea (Hearing)
…in the Semicircular Canals (Balance)
…in the Nose (Olfaction)
The Selfish Gene
• Many think that animals act for the good of
the species.
• Others think that animals act for the good of
themselves.
• It turns out that animals act for the good of
their genes.
• In other words, “A human is just a genes
way of making another gene…”
Explaining Cooperation and
“Altruism”
• Female birds risk their own lives to save their
offspring
• Vampire bats with extra blood feed the babies of
neighbors
• Hyenas and Wild dogs let each other know when
they’ve made a kill to share the food
• Bees sting an invader (and kill themselves in so
doing) to save the hive
• Zebra and Giraffe sharing the watch at water hole