There is a “pervasive reluctance of
teachers to forthrightly explain evolutionary biology.” Thus
conclude Berkman and Plutzer (2011) from their national survey
of high school biology teachers. Among “strategies for avoiding
controversy” are teaching various aspects of microevolution
(e.g. molecular biology) and “completely ignoring”
As noted in the survey, many high school teachers receive their
undergraduate education at non-research institutions that do not
offer special evolution courses. But many of the instructors at
such non-research institutions have themselves been trained at
research-intensive institutions. This is where I believe the
problem is rooted. The focus is on preparing future graduate
students to contribute to the highly competitive “cutting edge”
research carried out in laboratories such as those of their
instructors. The academic goals of other students are taken less
seriously. Furthermore, rather than simplify, the instructors
tend to qualify and hedge so as to afford little ground for
suspicion that they might have not mastered a subject fraught
with exceptions and apparent paradoxes. This arises, not from
professorial pedantry, but from the habit of self-marketing that
arises in the Darwinian struggle for career advancement known as
peer review (Forsdyke, 2000).
Beyond the constraints imposed by peer
review lie decisions on the importance of various aspects of
macroevolution and the best order in which they should be
presented. Too often there is presentation of a complex pageant
of life forms – wiggling nematode worms, gracefully contracting
jelly fish, cuddly koalas – rather than the seeking out of key
elements common to all these forms. Too often
In short, I maintain that the teaching
at research-intensive institutions casts a deep shadow over that
at lesser institutions. This finds expression in surveys such
that of Berkman and Plutzer (2011). Since the
modus operandi of
research-intensive institutions is unlikely to be remedied in
the near future (Forsdyke, 2000), what is to be done
now about teaching
evolution in high schools? An approach utilized for many decades
by “Ph.D.-toting” professors such as myself, has been to speak
while concurrently writing on transparent sheets displayed on a
screen above the blackboard. If carried out correctly, the
student feels that he/she and the instructor are sitting
side-by-side, however big the class. But it is still the
instructor, not the student, who determines the pace.
Software that overcomes this problem and facilitates
self-directed internet learning has been ably exploited by Khan
(Kiladze, 2010). After education at research-intensive
institutions (MIT and Harvard), Khan began making videos to help
a relative with her maths homework. This soon blossomed into a
major one-man YouTube enterprise that gained wide media
attention and support from the Gates Foundation. Students see
multicoloured drawings, arrows, numbers and letters, moving
across a black background to Khan’s melodious vocal
accompaniment. With pause and rewind options, they can proceed
at their own pace. Although laced with warm earnestness rather
than humor, Khan’s courses have spread worldwide and volunteers
have translated them into many languages. Inspired by the
success of initial offerings in mathematics, physics, economics
and high finance, Khan expanded into history (the French
revolution), and biology. Here, presumably guided by his
undergraduate lecture notes, biological terms are clearly set
out. Students should do well in examinations set by busy
instructors who pose questions that can be marked by graduate
students or computers. Comprehension of principle often does not
fall in this category.
While lacking Khan’s eloquence, in twelve short YouTube videos I have moved from overhead transparencies to a pen-tablet in order to explain evolutionary principles in everyday terms and, hopefully, with a touch of humor (Forsdyke 2011a; http://www.queensu.ca/academia/forsdyke/videolectures.htm). Organisms are portrayed abstractly as collections of characters. Thus the videos begin with a vertical arrow from organisms A with a particular set of characters to organisms B where many of these characters have changed. This is linear evolution. The line is then depicted as a recurring cycle – gamete to child to adult to gamete. Through ongoing variation, there is a constant pressure for branching into two independent cycles that will each tend to follow linear trajectories. However, branching is usually frustrated. Linear evolution is frustrated branching evolution.
This frustration arises in two ways. When branching lines are of
different fitness, members of one line tend to degenerate, so
reproductively isolating them from members of the other line,
which hence will interbreed only with their own kind. In this
circumstance, the rate of evolutionary change is high. On the
other hand, when branching lines are of equal fitness, members
of the two lines are not reproductively isolated and so can
interbreed. Characters may then tend to blend in children and
slow the rate of evolutionary change. Here the temptation to get
into the intricacies of blending and non-blending inheritance is
resisted. The blending idea is simple and intuitive, and amply
serves our purpose.
Also resisted is the temptation to
move too early to branching evolution. Our vertical arrow from A
to B depicts two types of temporal change – in form and
function, and in reproductive compatibility. When compatibility
fails, new species can arise. At some point a prototypic B form
(proto-B) would have become reproductively incompatible with the
ancestral form A. If they could have been crossed, either no
child would have been produced or, if produced, that child would
have been sterile and hence unable to continue the line. A new
species would have emerged. Even if not spatially separated, the
reproductive isolation between A and proto-B, arising from their
temporal separation, would have prevented their blending, thus
facilitating progression to reproductive incompatibility. But
how is this fanciful idea to be tested? How is a distant
ancestor to be crossed with a much later descendent? There is
here digression to a “thought experiment” based on Michael
Crichton’s novel
The videos then consider the segments in the unitary
generational cycle where it can be interrupted to produce two
separate, reproductively isolated, cycles. These have the
potential to lead to organisms that have diverged both from
their common ancestral form, and from each other. It is shown
that early arising mechanisms of reproductive isolation can be
over-ruled (pre-empted) by later arising mechanisms. Temporal or
spatial separations may initially cause reproductive isolations,
but not reproductive incompatibilities. Later these externally
arising isolations may be superseded by reproductive
incompatibilities arising from internal changes within the
organisms themselves. Prior external causes then become
irrelevant. On the other hand, sometimes internally-arising
reproductive incompatibilities develop first. These
reproductively isolate as effectually as external separations,
so that reproductive isolation and incompatibility appear
together.
Next, the videos turn to the likely number of genes
corresponding to the three main segments of the unitary
generational cycle. These segments are concerned, successively,
with transmission of gametes, development, and formation of
gametes for the next generation. Assuming genes to have equal
probabilities of mutating, it is argued that failure in the
small number of genes required for gamete formation is
insufficient to account for the frequency of failure of gamete
formation as a mechanism for internally-arising reproductive
isolation. Instead, non-genic mechanisms are invoked. This
leads, in the final videos of the series, to consideration of
DNA, chromosomes, cell division, and the somatic cell/germ-line
cell duality. Little chemical sophistication is expected. DNA is
composed of four building blocks (4 colored balls) and each
protein is composed of twenty building blocks (20 colored
balls). When there is variation, one of these colors mutates
into another. These variations may bring about both changes in
characters that relate to the form or function of an organism,
and changes in reproductive compatibilities.
From the above, it can be noted that
terms such as zygote, base, amino acid, mitosis, meiosis,
allele, clade, genome, genotype and phenotype are avoided.
Mendel is not mentioned, and Darwin and the term “natural selection” are
mentioned only briefly in a late video in the series. In a deep
sense, students already
know – have an intuitive understanding of – the principles
of evolution. The videos try to elicit this. If the videos
succeed, students should then be encouraged to master the
terminology and study more deeply (Forsdyke, 2001, 2011b; Cock &
Forsdyke 2008). Thus, the videos should serve the various
constituences in different ways. Students, at high school and
above, may find them a useful supplement to their biology course
materials. Instructors at various levels may find they provide a
useful template regarding what is to be taught, and in what
order.
The first series of videos on evolutionary principles is
followed by a second series of videos on natural selection
and a third on blending inheritance - enter Darwin and Mendel.
These illustrate the point that the learning of a subject and of
its history should best go hand-in-hand. But that is another
story.
Berkman, M. B. & Plutzer, E. (2011). Defeating creationism in the courtroom, but not in the classroom. Science, 331, 404-405.
Cock, A. G., & Forsdyke, D. R. (2008).
Treasure Your Exceptions. The Science and Life of William Bateson.
Crichton, M. (1990).
Forsdyke, D. R. (2000). Tomorrow’s Cures
Today? How to Reform the Health Research System.
Forsdyke, D. R. (2001). The Origin of Species,
Revisited. A Victorian who Anticipated Modern Developments in
Forsdyke, D. R. (2011a) Evolutionary
principles in everyday language: Introduction. You Tube videos.
(
http://www.queensu.ca/academia/forsdyke/videolectures.htm )
Forsdyke, D. R. (2011b).
Evolutionary
Bioinformatics. 2nd Ed.
Kiladze, T. (2010). Too cool for school. Globe
and Mail. Report on Business.
Gregory, T. R. (2009). Understanding natural selection; essential
concepts and common misconceptions. Evolution Education & Outreach, 2,
156-175.
Thompson, C. (2011)
Wente, M. (2011) Teaching the Khan way.
Globe and Mail.
This page was established in July 2011 and was last edited by DRF 08 Dec 2014