Transcript The Unintelligence of Design

The Unintelligence
of Design
Terri Felton
Evidence for Evolution
March 28, 2006
The Argument:
“The theory of intelligent design (ID) holds that
certain features of the universe and of living things
are best explained by an intelligent cause rather
than an undirected process such as natural
selection…
In a broader sense, Intelligent Design is simply the
science of design detection -- how to recognize
patterns arranged by an intelligent cause for a
purpose.”
--Intelligent Design Network
For What Purpose?
Some Examples of Unintelligent Design
“The Panda’s Thumb”
• Five digits, plus a
“thumb”
• Used for grasping
bamboo – a “channel”
between two pads on
the forepaw
• Question: Was this
structure “designed”
this way?
Photos: bcps.org, giant-panda.com, mccullagh.org
Not a Digit
Photo: Athro, Limited
• Enlargement of the
radial sesamoid
• “True thumb” is 1st
digit; not opposable
• Musculature
responded to
sesamoid growth,
allowing it to function
as a “thumb”
• Tibial sesamoid also
enlarged
The Argument:
• The panda, as a relative of carnivorous
bears, developed its “thumb” through
natural selection for grasping bamboo
• If pandas were originally designed to have
opposable thumbs, wouldn’t they have
structures similar to primates, which are
more efficient?
• How might this argument be countered?
Human Examples
Lowered larynx in
humans versus primates:
Adapted for speech, but
creates increased risk for
choking
Illustration: Martin Nickels, 1998
Small pelvic opening
necessary for
upright walking (legs
close together)
Large skull size to
accommodate larger
human brains
Illustration: Martin Nickels, 1998
Recurrent Laryngeal Nerve
• Originates from the
vagal nerve, then
extends down the
neck into the chest,
and then back up to
the neck again
• In fish, this nerve
follows a straight line
Illustration: www.voiceproblem.org
The Vertebrate Eye
Retina is “inside out”:
• Photoreceptor cells point
away from light, with the
“wiring” passing through
the retina to create a
blind spot
• Why might the eye be
“designed” in this way?
Illustrations: wikipedia.com
The Arguments:
Evolution argument:
• Inverted retina resulted from the development of
a neural tube out of an originally flat, lightsensitive layer
• PBS Evolution Library: The Eye
Opposing argument:
• Retina is inverted to take advantage of the
nutrient-rich capillaries just outside the
photoreceptors
How might one respond to either argument?
Vestigial Structures
Evolution would also predict that species
occupying very distinct environments from
that of a common ancestor might show
vestigial structures — structures obtained
from a common ancestor but no longer
needed for the original adaptive function.
Rudimentary tooth in lower
jaw of a baleen whale
Sources: top - Young, 1992; lower http://www.lclark.edu/~seavey/genetics04/home.html
The pelvic girdle seen in reptiles
and mammals as an adaptation
for support in tetrapods, is
vestigial in whales — it is a
“fossil” footprint of their
ancestry and serving no function
today in swimming descendants
of tetrapods.
Vestigial Structures
Wings on flightless birds
• Balance for running
• Courtship displays
• Why wings?
Eyes on blind cave fish
• Surface-dwelling species
has fully-functioning eye
• What purpose does the
eye serve in the cavedwelling species?
Photos: livescience.com
Vestigial Structures - Plants
Parasitic and non-green dodders retain
“fossil” non-functional chloroplasts
(photosynthetic organelles) with reduced
cpDNA in their cells as a vestigial
structure inherited from a common
ancestor with morning glories
Cuscuta - dodder
Ipomoea - morning glory
Source: Ken Sytsma
Vestigial Organs - Humans
Appendix:
• Left behind from a planteating ancestor?
Tailbone:
• May support pelvis and
anchor minor muscles
Wisdom Teeth:
• Ancestral jaws larger?
• Better hygiene?
Illustrations: livescience.com
Vestigial Behaviors
Erector pili muscles:
• Cause hair to stand on
end to make one look
larger and keep the body
warmer
• Humans have less body
hair than ancestors
• Why might this behavior
remain?
Illustration: BBC Eureka TV
Photo: www.hunterian.gla.ac.uk
Questions for Discussion:
• Does the work of a “designer” imply
perfection?
• Does imperfection in and of itself provide
evidence for evolution?
• How does one provide evidence for
evolution through the imperfections given
in this presentation?
• What might be some counterarguments?
Resources
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Davis, D. Dwight. The Giant Panda, a Morphological Study of Evolutionary
Mechanisms. Chicago Natural History Museum, 1964.
Dawkins, Richard. The Blind Watchmaker. New York: Norton and Company,
1986.
Denton, Michael J. “The Inverted Retina: Maladaptation or Pre-adaptation?”
Origins & Design 19:2 Issue 37.
Gould, Stephen Jay. The Panda’s Thumb: More Reflections in Natural
History. New York : Norton, c1980.
Nickels, Martin. "Humans As a Case Study for the Evidence of Evolution“.
Reports of the National Center for Science Education 18(5), Sep/Oct, 1998,
pp.24-27.
Young, David. 1992. The Discovery of Evolution. Cambridge Univ Press.
http://www.athro.com/evo/evframe.htmlht
http://www.livescience.com/animalworld/top10_vestigial_organs.html
http://www.nyu.edu/projects/fitch/courses/evolution/html/examples_of_adapta
tions.html