the Summer of 2009
Articles in Special Edition
Evolution: Education Outreach Journal
(Scroll down to bottom of page "How To Find Articles")
Information for teachers - current status
Transitional Fossils, Natural Selection Myths,
Review by Larry Flammer
If you haven't checked out the awesome list of articles in
the latest volume of Evolution Education Outreach Online,
you need to go there! It's a special issue featuring Transitional
Fossils. And best of all, the authors are all specialists
in their fields, but writing primarily for biology teachers in
relatively non-technical language, and pulling together broad
collections of information, including recent data and interpretations.
Having developed and extended my whale evolution lessons,
I was especially interested in reading "From Land to
Water - the Origin of Whales, Dolphins, and Porpoises"
by Thewissen, et al. Indeed, the article was very helpful. It
brought in an extended discussion of the recently processed fossils
of Indohyus as a member of the extinct artiodactyl group
known as Raoellids, a much more likely pre-cetacean group than
the mesonychids. Many other details about informative features
in the groups of whale antecedents are well presented, including
bone thickness, oxygen isotope ratios in teeth, comparisons of
ear bones, semicircular canal size, nasal bone reduction, and
sizes & positions of orbits and other skeletal features.
Many clues about the likely environments for these creatures
are also included. The many diagrams and photos help to make
the article accessible for any students doing the Becoming
Whales and Whale Ankles and DNA lessons who may want
to explore the subject further and see what the current thinking
is about cetacean evolution.
A natural extension from this was Donald Prothero's article
on Evolutionary Transitions in the Fossil Record of Terrestrial
Hoofed Mammals (since Indohyus and the earliest pre-whales
with feet all had hooves). The number of examples of many transitional
series of fossils was most impressive. In a time when creationists
repeatedly assert that one of evolution's weaknesses is that
there are no transitional fossils, it was refreshing to see how
much progress has been made here. In reality, there have long
been many such collections, but new material in recent years
has filled in even more details, and added more series, for both
perissodactyls and artiodactyls. The article makes a strong case
for the reality of the "bushiness" of family trees,
encouraging us all to point this out to our students, that the
long-outdated linear idea of evolutionary chains, with their
"missing links" is totally inconsistent with the fossil
record. Examples include the abundance of material for the evolution
of horses, rhinos, tapirs, camels, giraffes, and elephants. In
all cases, the earliest members of each group are practically
indistinguishable from each other, becoming gradually and increasingly
different over time, just as we would expect from the process
of evolution, and totally inconsistent with traditional ideas
about the origin of diversity.
Another group that all biology teachers should explore is
the Pre-Mammal group of tetrapods. Read the article by Kenneth
Angielczyk, "Dimetrodon is Not a Dinosaur: Using
Tree Thinking to Understand the Ancient Relatives of Mammals
and their Evolution." The author explains how an understanding
of evolutionary trees and how they are currently built, provides
a very useful tool to help students to see that the easily recognized
fin-back synapsid known as Dimetrodon is clearly not a reptile,
but rather a member of a large bushy series of tetrapods that
began evolving away from their early tetrapods many millions
of years before reptiles began to appear from a different group
of tetrapods. Those pre-mammal synapsids document the gradual
appearance of an increasing number of mammalian traits over 100
million years. For any student who raises the erroneous challenge
of "where are the transitional animals between reptiles
and mammals?" - you could offer this article to read, summarize,
and reflect on the question. In fact, it wouldn't hurt to require
any AP class to read this.
Of course, this all just whets the appetite for more! With
the recent discovery of Tiktaalik - the fish with wrists
- in contrast to the detractors' claim of "lack of 'convincing'
evidence" for how land animals could have evolved from fish,
I had to find out what was new in that arena. Jennifer Clack's
article "The Fish-Tetrapod Transition: New Fossils and
Interpretation" does this well. Again we see, as we
would expect, that the more fossils we find from the period where
transition must have happened, the fuzzier it becomes. There
are increasing numbers of fossils where lobe-finned fish begin
to show some tetrapod features over time, and the earliest clear
tetrapods still have some fish features. This makes it increasingly
more difficult to say just when we have a tetrapod-like fish,
and when we have a full-fledged tetrapod. As in all cases of
transitional forms: they are always a shifting mosaic of the
earlier features being gradually replaced by the newer features,
precisely as predicted by evolution.
There are several other articles that might be of interest,
but I turned next to another area of interest, beautifully presented
in an article by T. Ryan Gregory: Understanding Natural Selection: Essential Concepts and Common Misconceptions." Since
I have made a career of deeply incorporating evolution into my
biology course, including pointed efforts to attack popular misconceptions,
I was interested in seeing if my coverage had been accurate and
appropriate, and had I overlooked any critical misconceptions.
For the most part, it looks like I did ok. The paper discusses
the extent and possible causes of misunderstandings of the process
of natural selection, and presents a review of the most common
misconceptions that "must be corrected before a functional
understanding of natural selection and adaptive evolution can
be achieved." I did discover that I probably didn't emphasize
certain points as much as I should have. As a result, I will
be doing two things: 1) review our "Evolution Knowledge Survey" pre-test instrument, to see if it contains checks
on several critical points described in the article, and 2) review
all of our natural selection lessons to be sure that teachers
are urged to emphasize those critical factors in their discussions
following the activities.
If you print and read any of the articles in this online volume,
make it this one, on the many misconceptions about Natural
Selection. From many studies cited, it is clear that natural
selection is, in general, very poorly understood - even by those
who have postsecondary instruction in biology! In fact, most
disconcerting is the fact that "confusions about natural
selection are common even among those responsible for teaching
it." "One cannot assume that biology teachers,
with extensive backgrounds in biology, have an accurate working
knowledge of evolution, natural selection, or the nature of science."
How about you? Is it time for a reality check? The article does
a very nice job of summarizing just what natural selection is,
as understood by evolutionary biologists today. This description
is accompanied by an excellent graphic that shows Darwin's 5
observations and 3 inferences that comprise his theory for natural
selection as the main mechanism for evolution. The author explains
in detail why natural selection (contrary to its detractors'
assertions) is a non-random process. He shows that natural
selection is a two-part process, with a random component (mutations)
and a non-random selection component (differential survival and
reproduction). He also suggests that the random component of
natural selection (mutation) might be less confusingly called
"undirected" rather than random, and that most mutations
are neutral (not detrimental, as widely assumed). A distinction
is made between Darwinian "fitness" and the more familiar
usage of "physical fitness," and how confusion of those
terms is probably one of the causes for misunderstanding. The
author clearly explains why "Survival of the Fittest"
is misleading, and why natural selection is not a tautology (case
of circular logic) as some critics have suggested. The misuse
of "adaptation" is discussed, as is the concept that
it's populations that evolve, not individuals. It's also explained
why mutations do not occur "in order to" improve fitness,
and why evolution and natural selection are not the same thing.
Lots of good stuff here to sharpen your evolution unit.
Gregory explains possible reasons why natural selection is
notoriously so difficult to grasp accurately, while being deceptively
perceived as being elegantly simple in principle. While pointing
at the anthropomorphisms and suggestions of intent that are often
included in descriptions of natural selection, along with the
idea of Use and Disuse often ascribed to Lamarck, he also
points out that those deep-seated ideas actually preceded Lamarck,
while Lamarck contributed many useful and accurate ideas, along
with the first (albeit ultimately incorrect) mechanistic theory
Again - this should be a "Must Read"
selection for all Biology teachers this Summer. And if you develop
any kind of interactive lesson based on any of these articles,
please share with ENSI so other teachers can benefit.
There are many more great articles.... I can't overlook Louise
Mead's article on "Transforming Our Thinking About Transitional
Forms." She makes a strong case for why finding or searching
for "The Missing Link" is so inappropriate for the
branching tree nature of evolution. Long-outmoded ideas about
the "evolutionary ladder" and the "chain of being"
in which every creature has a position in a lineal ancestry must
be explicitly discredited. Instead, focus must be put on the
characteristics or features that have changed over
time rather than the individuals represented by fossils. Suggesting
that fossils represent individual species in the direct line
of ancestry to modern species (or "forms") is just
inconsistent with reality. Fossils represent groups of
organisms that share various numbers of certain traits with other
fossils and living groups, and it's the changes and shifting
balance of those features in groups over time that provides
the most compelling picture of evolutionary change. "Missing
Links" have no place in this paradigm whatsoever. Mead cautions
us to avoid using "link-thinking" terms like "primitive"
vs "advanced", or "higher" vs "lower,"
and replace them with "ancestral" and "derived."
Promote "tree-thinking" and focus on features, not
forms or organisms. She also offers a number examples of the
compelling power of multiple independent lines of evidence, and
how important it is point this out clearly to your students.
Most of the ENSI lessons make a point of doing just that.
Finally (for now), another must-read article in this online
volume is "A Name by Any Other Tree" by Anastasia
Thanukos. She provides an excellent introduction to the value
of tree-thinking and the use of cladogams for understanding evolution,
and to realize that cladograms show realistic relationships among
diverse groups. "Students need to know that the guiding
principle of modern classification has to do with common ancestry
and the nested hierarchy formed by the tree of life." "Memorizing
the ranks is much less important than understanding the
concepts of clades and common ancestry." "When classifying
hardware [as many students do], all classification schemes the
students come up with will be equally valid - but the same is
not true in biology." [The ENSI lesson "Nuts & Bolts Classification..."
nicely addresses this issue.] Also, see the 2008 ABT article
by Baum & Offner: Phylogenies
& Tree-Thinking, with excellent links fo related
HOW TO FIND THE ARTICLES:
Click Here for direct link to this volume (2, issue 2, June, 2009). This will
take you to the list of contents of 21 articles from which to
choose. For the selected article, click on its "PDF"
link to download a printable copy.
NOTICE: This journal is now FREE to all users, thanks to publisher Springer (as of Dec. 2013). If you want to search through any of the other volumes/issues of the Evolution: Education & Outreach journal, you'll be happy to hear that it is now "Open Access", FREE to all users. Just click here: Evolution: Education and Outreach - Springer. and you can select the volume and issue number desired. Actually, to see a list of all volumes and issues to date, along with the topics focused on for each issue, click on Evo Ed & Outreach Topics. You can click/access any issue in the list to go directly to that issue.
FOR USABLE FIGURES:
If you want to use some of the figures for a PPT presentation
or overhead, use the "VIEW" (HTML) version - the figures are sharper and
can be clicked and dragged to your desktop. If those aren't sharp
enough, maybe you could email the author and nicely request a
sharper JPG version of certain desired illustrations. The email
address for each author is included in the article, and I suspect
that they would be happy to comply if you explain what you are
trying to do. Or email the webmaster.
A couple of the authors have sent me high res versions of some
of their diagrams. Just be specific in your request.
Again, if you should develop any clever interactive lessons
using this material, please share - send a copy to me to consider
adding to the ENSI site for easy access by other teachers. You
will, of course, be given all due credit for your lesson.
FOR PDF VERSION OF THIS REVIEW
If you are looking for
new ways to introduce evolution,
for some of our suggestions.