Icons of Evolution
A Critical Review
by Tony Hiatt
Tony has created an excellent 45 frame PowerPoint presentation
of a critique of Jonathan Wells' "Ten Questions to Ask Your
Science Teacher", popularized in his book Icons of Evolution.
This was the core of Tony's presentation at the Science Teachers
Convention in Indiana a few years ago. Many of the frames have
colorful illustrations along with the informative text, which
includes the scientific response to each "Icon",
along with ideas and links for how teachers can address each
Question in the classroom, or even create an atmosphere
where such challenges are not so likely to be raised.
Below are a few sample frames from the series to give you
an idea of its content. If you would like to see the complete
presentation, condensed in a PDF
file, click here (7 pages). If you would like to get
the entire PowerPoint series of slides (including illustrations),
as a PowerPoint file, which you can use to present to a group
of teachers in your area, just contact the ENSI webmaster, and it will be sent
to you as an email attachment.
The PowerPoint set could also be presented to students if
a comprehensive, detailed yet tactful treatment is desired, but
you might want to omit (or click past) the "Dealing With
"Icons" in the Classroom" pages. However, as Hiatt
points out, the best, least confrontational approach is probably
to be "pre-emptive", by simply providing your students
with experiences which they can draw upon to answer questions
like those in Wells' "Icons" before they are
even asked.
slide #4
This Review Has Three Purposes
· Summarize Wells' claims for each icon and his "10
Questions to ask your biology teacher."
· Summarize the responses from the scientific community
to each icon.
Provide teachers with ideas, lessons and resources for providing
their students with the background for answering Wells' questions
themselves. |
slide #5
Dealing With "Icons"
in the Classroom
A pre-emptive approach is always preferable to a rebuttal approach.
Provide your students with experiences that they can draw upon
to answer Wells' questions before they are even asked.
A strong background in the nature of science is essential. This
means going well beyond the over-simplified coverage of the scientific
method found in most texts and using activities that are student-centered
and are designed to simulate the nature of science.
Stay informed. Textbooks are often out of date and do contain
mistakes. |
slide #9: (with figure of a Cambrian sea bed)
|
Icon # 2 Darwin's Tree of Life
and the Cambrian Explosion
Question to ask your biology teacher # 2. Why don't textbooks
discuss the "Cambrian Explosion," in which all major
animal groups appear together in the fossil record fully formed
instead of branching from a common ancestor thus contradicting
the evolutionary tree of life?
Wells claims that the fossil record and molecular evidence
does not support Darwin's "Tree of Life" because:
. The Cambrian explosion suggests the sudden appearance of major
animal body plans in direct conflict with Darwin's "gradualism."
· There was no evidence of multicellular life until "just
before" the Cambrian Explosion.
· Phylogenetic trees based on DNA evidence are problematic.
· Molecular clock evidence for the common ancestor of
all animals is inclusive.
|
slide #10
|
The Scientific Response
· Darwin's use of the word "gradual" meant
'stepwise' and not necessarily 'slow.'
· Modern evolutionary theory does not require slow accumulations
of changes particularly in the evolution of body plans (Hox genes).
· The period of time Wells refers to as "just before"
the Cambrian actually represents 40-70 million years.
· Major groups not included in the Cambrian Explosion
are insects, amphibians, reptiles, birds and mammals.
· The "Tree of Life" is about evolutionary relationships,
not timing.
· Textbooks DO discuss the "Cambrian Explosion."
· Wells' argument for the failures of phylogenetic trees
is based on quoting scientists out of context about methodological
problems while ignoring these same scientists' conclusions and
avoiding examples of its wide success.
· Even though there have been some discrepancies in the
molecular clock results they all agree on a common animal ancestor
at the very least 160 million years prior to the Cambrian Explosion.
|
slide #11
|
Addressing Icon # 2 in the
Classroom
· Tree of Life Web Site
http://tolweb.org
· ENSI Web activities that involve using molecular data
to construct cladograms and phylogenetic trees.
www.indiana.edu/~ensiweb/evol.fs.html
· Molecular Connection activity
www.pbs.org/wgbh/evolution/educators/teacherstuds/pdf/molecular_connection.pdf
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