SUBJECT: Examples of "we used to think that..."
DATE: 1/97
 
Hi Biolabbers,
 
I've recently been discussing the scientific method with my General Bio
class and in a nonmajors class. We always talk about "supporting"
hypotheses and not proving them and some students resist this notion. I
usually point out some "totally ridiculous" belief from the past that was
widely held, but now is clearly not true. The flat earth hypothesis is
one of my favorites since now MOST everyone accepts that the earth is
more or less round. I have a couple of others that I use too,
spontaneous generation etc., but I'm looking for some new ones to try
out. Does anyone out there have any favorite "gee whiz of course not"
examples? Thanks for your ideas.
 
Guy Farish
Biology Department
Adams State College
Alamosa, CO 81102
(719) 587-7969 FAX (719) 587-7242
 
 
1. Ecological succession always ends in a stable climax ecosystem.
 
2. Genes are indivisible particles.
 
David J. Hicks djhicks@manchester.edu
Biology Dept., Manchester College
 
 
I recall seeing on an earlier Biolab post that it was widely held not too long ago (1940's? 1950's?) that the human chromosome number was thought to be a number other than 46 -- Is
48 the value I recall? Anyway, it makes a nice point about the tentative nature of science and how
advances in technology and scientific knowledge cause "truths" to become outdated. Our current
definition of what a chromosome is may have something to do with this dichotomy. Perhaps someone out there can provide you with more of the requisite details?
 
"Science is built of facts the way a house is built of bricks;
but an accumulation of facts is no more science than a
pile of bricks is a house."
- Henri Poincare
 
Todd Bennethum, Science Teacher
Arapahoe High School
2201 E. Dry Creek Road
Littleton, CO 80122
 
 
In answer to your post in biolab about human chromosome number:
 
The problem lies in the technique--or lack of technique-- to spread the
chromosomes out well enough to count them.
 
Ricki Lewis summarizes the situation nicely in her book, Human Genetics:
Concepts and Applications. Published by WC Brown.
 
According to Lewis, in 1923, Painter published a study of the human
chromosomes in which he counted 48. This was considered the accepted
number, but other studies came up with numbers ranging from 38 to 48.
 
The problem was being able to spread the chromosomes out enough so they are
not touching each other to be able to see them and count them.
 
Improvements in techniques included:
 
the use of colchicine to arrest cells in metaphase, when the chromosomes
will be most condensed.
 
the use of a hypotonic solution to swell cells and spread the chromosomes
out more. This was discovered in 1951 when a technician made a mistake and
made up the wrong salt solution. The beauty of science is being able to
recognize the significance of a mistake!!
 
further improvements to spread chromosomes out more, including the dropping
of the cells onto a microscope slide to spread the chromosomes out better.
This was found in 1953.
 
By 1956, the number of 46 chromosomes in the human diploid cell was settled
upon. Levan and Tjio were the researchers who did that study.
 
 
This is a fascinating story; one that I share with my sophomore genetics
students.
 
Sue Karcher
 
 
Susan J. Karcher, Ph.D.
Instructor in Biological Sciences
Purdue University
West Lafayette, IN 47907-1392
 
 
 
My favorite example of a scientific "truth" that seemed beyond all
questioning, but turned out to be wrong is Newtonian mechanics. It ruled
physics for over 200 years, but was superseded by quantum mechanics and
relativity. Are any of our current paradigms just as wrong? Who knows?
Another example, more biological, is the conviction that proteins carried
genes. This too was "obvious", so obvious in fact that Avery's experiments
that proved this idea wrong were not generally accepted for about 8 years,
when they were confirmed by the Hershey-Chase experiment. A current
example is the ongoing bruhaha over prions. These are infetious particles
that have no genes, yet can "reproduce" and cause diseases like kuru and
"mad cow disease". They threaten to bend our concept of organism.
Science operates, not by proving theories right, but by proving all
"reasonable" theories wrong except for one. The reason that scientists are
sometimes very wrong for so long is that the real answer seems so unreasonable
that it doesn't get tested properly until something odd comes up to force the
issue.
 
Jim Eliason
Biology Dept.
Manhattan College/College of Mount St. Vincent
Riverdale, NY 10471
 
 
Guy:
 
For silly past "truths" how about:
 
1) using cannons in New York to disturb the bad air that was causing enteric
diseases (typhoid,cholera, etc)
2) the earth as the center of the solar system
3) using hysterectomies to calm hysterical females
 
Have fun!
 
Emily Rock
 
 
How about the notion that the earth goes around the sun and not vice
versa.... Challenge your students to convince you that former is
true -- not as easy as you may think!
 
Graham R. Kent
Bioogy. Dept.
Smith College
Northampton, MA
 
 
When it comes to ideas once (?) held to be obviously true,
how about "men are smarter than women"?
Chester Wilson (c9wilson@stthomas.edu)
biology
University of St. Thomas
St. Paul, MN
 
 
A student of mine in a non-majors class made an interesting comment last
week after class. We had just finished a discussion over scientific method
and philsophy of science etc. His question was: "So modern day science is
everything we haven't proven false yet?" What a wonderful comment. I told
him that I might steal it from him and use it later on in class
 
He had come up with some other interesting comments when we differentiated
science and philosophy, so I asked him about his background. He and spent
the last year in a Jesuit seminary studying philospphy. Now I have to be
on my toe's when I make a comment about philosophy etc in his presence
since he has a much better backgtound there than I do.
 
===========================================================
When A scientist isn't sure of what he's doing, he calls it research.
I must do a lot of research
 
Terry Davin
Biology and Allied Health
Penn Valley Community College
Kansas City MO 64111
davin@kcmetro.cc.mo.us
(816) 759-4236 (PHONE)
(816) 759-4553 (FAX)
 
 
19th century doctors were taught that men & women breathed differently:
 
Men used their diaphragms to expand their chests, whereas women raised the
ribs at the top of the chest. Finally, a female doctor found that women
breathed this way because their clothes were so fashionably tight!
 
Mike O'D
 
**********************************************************************
Michael A. O'Donnell
Dept. of Biology
Trinity College
300 Summit St.
Hartford, CT 06106-3100
michael.odonnell@mail.trincoll.edu
http://www2.trincoll.edu/~odonnell/
phone: (860)297-2228
fax: (860)297-2538
 
 
Examples of well-accepted ideas in biology changed by new knowledge:
1. only 2 types of cells -- prokaryotes and eukaryotes (add Archaea)
2. genes are continuous sequences of amino acid-encoding codons (introns)
3. Barbara McClintock and the idea that genes can jump
4. widespread concept earlier in the century that protein is the genetic material
(here you can show the neat experiments to disprove this -- Hershey & Chase, etc.)
 
And yes, the human chromosome # was first thought to be 48.
 
Ricki Lewis
76715.3517@compuserve.com
 
 
How about "spontaneous generation"?
 
***************************************************
Ed Alkaslassy (503) 359-2967
Dept. of Biology FAX: 503-359-2933
Pacific University <alkaslae@pacificu.edu>
Forest Grove OR 97116
 
 
How about the "Central DOGMA" of biology, having DNA coding for RNA,
and then the discovery of reverse transcriptase and RNA as template
for DNA sythesis?
 
Hildy Sanders
Villa Julie College
Stevenson, MD 21153
f-sander@mail.vjc.edu
 
 
Hi Guy and Biolab,
 
Rather than going for the single "disproven" examples, it might be nice to
more realistically convey the "evolving" nature of scientific knowledge. For
example, you can explain (or have them explain) the gradually improving
theory of how the continents came to be, from the mythological ones, on up to
continental drift, to the current plate tectonics theory. I learned this
from a 6th grade science teacher who assures her students that as "stupid" as
the old theories sound, plate tectonics is only the best explanation we have
right now, and in the future it too may seem silly. This also helps students
to accept their own evolving ideas--like recalling the days when they
"stupidly" thought zero was the smallest number.
 
A more relevant example to our college biology students is that of the
development of "the central dogma" of RNA->DNA->protein, how that idea came
to be, and how it is now known to NOT be dogma--that exceptions abound
(retroviruses). Another really good story about the evolution of ideas
about DNA is what happened when an old-fashioned, solo-working, geneticist of
field corn proposed that the then vogue view of DNA as a static, permanent
cellular structure was inadequate, that her calculations of mutations in her
specimens indicated that the genome was much more dynamic. Barbara
McClintock was laughed out of the chic genetics meetings of the 50's, only to
be awarded the Nobel prize in the 80's for her proposal of transposable
elements, or "jumping genes". Not only does this indicate that experimental
and naturalistic inquiry should and do meet, but that by now we should know
better than to say "no way!". Ideas change fast, and explanations improve,
but as more pieces of the puzzle begin to fit, we see that our puzzle doesn't
really have that straight edge, it really will meet up with someone else's
puzzle.
 
By the way, I don't think physicists have declared Newtonian physics "wrong",
just not universal. Relativity and Quantum Mechanics have merely IMPROVED on
Newton's limited explanation of force and matter. They are now relevant to
places in the universe light years away rather than just on our earth and
nearby where space and time "seem" linear.
 
For what it's worth,
 
Phyllis Baudoin Griffard
Doctoral Fellow in Biology Education
Louisiana State University
griffardp@aol.com
"Education is a series of diminishing deceptions"
 
 
Genetics gives another great example of how solid older studies may be
supplemented rather than displaced by newer findings. Discoveries since 1900
don't disprove Mendelian genetics, they just show that Mendel's "laws" are
far less than the whole picture.
 
David J. Hicks djhicks@manchester.ed
Biology Dept., Manchester College
 
 
The best example I always use is the discovery that most ulcers are caused by
Helicobacter not stress. Since it was run through the mass media, many
students all ready have some knowledge of this, but it is a dramatic, recent
example.
 
Brent deMars
Lakeland Community College
 
 
Thank you, Brent, for bringing up the ulcer question. This one has been
bugging me, and now I have an excuse for asking. Why can't both
explanations be correct? Where does the Helicobacter come from? Is it
one of those bacteria we carry around with us with no problem until
something goes wrong? Couldn't stress in some way permit this bacterium
to multiply, causing the ulcerations? And couldn't we then get rid of the
ulcer by treating the bacteria? This is a wonderful example that I have
used with my students to talk about paradigms, but I don't feel that
stress is an irrelevant part of the story and don't want to throw it out
without more evidence that it is unrelated.
 
Janice
***********************************
Janice M. Glime, Professor
Department of Biological Sciences
Michigan Technological University
Houghton, MI 49931-1295
jmglime@mtu.edu
906-487-2546
FAX 906-487-3167
 
 
Janice,
As far as I know, Helicobacter is not part of normal GI flora. In
fact, one of the early clincher Koch's postulate type experiments was done
by one of the researchers on himself. He ingested a quantity of the
bacteria, and sure enough, ended up with an ulcer in a short time. Upon
antibiotic therapy, the ulcer disappeared. The route of infection and
portal of entry for the bacteria is still not clear. There was a pretty
good non-technical article in Scientific American about a year or so ago.
It should be suitable for undergrad reading. At least from what I've read
(and I'm no expert) it seems to be more of an example of an acute infection
that can cause other problems if it becomes chronic. The stress hypothesis
to me has always seemed like another one of those "If you can't pin point
the cause - call it stress or a virus" types of explanations.
 
Liane
 
Liane Cochran-Stafira
Dept. of Ecology and Evolution
The University of Chicago
1101 East 57th Street
Chicago, Illinois 60637-5415
phone: 773-702-1930
fax: 773-702-9740
e-mail: lcochran@midway.uchicago.edu
 
 
Janice:
As to the Helicobacter, ulcers and stress:
 
If any where from 25% to 60% of healthy adults age 40 or older can carry it
around as "normal flora", then there must be other predisposing factors to
increasing the risk of ulcer formation. Apparently people with type O blood
are more susceptible to allowing the bacteria to attach to the stomach
lining. One of my micro textbooks says recent studies have shown that cats
may be a reservoir host. There is more to this than meets the
..Helicobacter!
 
Emily Rock
Orrville, Ohio
 
 
Here's a veterinary pathologist's take on the pathophysiology of gastric
ulceration. The bottom line is there are well-known stress-induced
mechanisms that contribute to the susceptibility of the gastric mucosa to
inflammation and ulceration. 1. Stress influences the release of
catecholamines (epinephrine and norepinephrine) from the adrenal medulla
and nerve cells. These neurotransmitters stimulate the release of gastrin
via cyclic AMPfrom enteroendocrine cells in the intestine and pancreas.
Gastrin causes the release of H+ by the gastric parietal cells, increasing
gastric acidity and converting more pepsin. 2. Catecholamines also
vasoconstrict gastric blood vessels, resulting in mucosal compromise. As
I tell my A&P students "if a tiger walks through the door, the last thing
your body is worried about is digesting your lunch!" 3. Catecholamines
also stimulate local gastric mast cells to degranulate, dumping their
histamine which attaches the H2 receptors on parietal cells. This also
results in the release of H+ into the gastric lumen. This particular
mechanism is what is being addressed by the flood of anti-acid medications
on the OTC market (Tagamet HB, Pepcid AC, Zantac 75), all of which are H2
receptor antagonists. My guess is Wall Streeters pop these routinely, even
as they watch their profits from pharmaceutical comglomerates rise! 3.
Prostaglandins are generally known to be inflammatory mediators. Yet in
the gastric mucosa they play an important role in mucus production (via
cyclic AMP) in the mucous epithelial cells, mediate gastric vasodilation
necessary for adequate circulation and modulate H+ release from the
parietal cells. Cortisol, released from the adrenal cortex in response to
stress, has an anti-prostaglandin effect. The main consequence is a
reduction in the protective mucus layer on top of the gastric lining,
allowing HCl and pepsin back diffusion which destroys the epithelial
cells. This is the mechanism by which NSAIDS (aspirin, ibuprofen, etc.)
result in gastric irritation as well.
 
As for the definitive underlying cause of peptic ulcer disease in humans,
it is up for grabs. Certainly, H. pylori has been shown to be a
contributing factor. Stress, for all the mechanisms described above,
seems to be less of a concern. Individual sensitivity to a variety of
causes might be the most acceptable, if least satisfying answer to date.
 
It is well-established that the reservoir for H. pylori is humans. Dogs
and cats have their own species of gastric spirochete, Gastrospirillium
sp. The notion that cats are the reservoir of H. pylori is the result of a
paper published in Infection and Immunity (June '94) in which a colony of
SPF (specific pathogen free) cats was found to be infected with H. pylori.
A more plausible explanation is that the cats, having a downgraded immune
system, picked up the infection from an infected caretaker (fecal-oral
route). When spiral bacteria are seen in a canine or feline gastric
biopsies (which is frequent) is it generally without any sign of
associated inflammation, and therefore reported out as "significance
uncertain".
 
Thanks,
 
Barb Lewis, DVM, MS
bclewis@lakeerie.edu

 
 
To the group:
The 46 chromosome story.
Winiwarter at the turn of the century was "the" chromosome expert. At
that time the chromosome number reported for humans varied from between
30 to 80+. Ole Wini decided that it must be 47 in males and 48 in
females because it was his opinion that humans had an XO sex
determination system. This report was in 1912. T.S. Painter started
looking at chromosomes around 1920. At about 1922 he had a former
student, now an MD, working at the Austin State hospital. The former
student knew of his interest in chromosomes and asked if Painter would
like human testicular tissue; the former student now performing
castrations on mental patients who openly masterbated at the hospital (it
was called "self-abuse"). Painter went over to get the fresh tissue. He
describe the state of the patients in his 1923 paper: one of the three
men went to sleep during the castration. Painter examined this tissue
and came up with two numbers 46 and 48. He ultimately chose 48. It was
most important to Painter to declare that humans had an XY sex
determination system instead of XO. Later in the '60's Painter was asked
about the possibility of the patient(s) having XYY or something like
that. He indicated that he thought his material was normal in that
regard. Painter won the XO XY battle which was what he was interested
in.
 
Later Levan was on leave at Sloan Kettering working with John Biesele
(Biesele having worked as a graduate student under Painter). Biesele
suggested to Levan how he might better see chromosomes from human tissue
culture. Tjio and Levan employed the technique and did see chromosomes
better and reported in 1956 the number of 46. The literature rippled for
about two years and by about 1958 settled on the number 46.
 
Kottler in 1974 wrote a wonderful account of this history in the Bulletin
of the History of Medicine. Painter talked of it all in a Stadler
lecture in 1969, the last year of his life. A student and I travelled
down these roads in a paper published last year in Bioscene (August
1996). John Biesele is retired in Austin and nearing 80. Levan is still
alive in Sweden and well into his '90's. I had the pleasure of being a
student of both Biesele and Painter.
 
For Sue and others:
Kottler, M.J. 1974. From 48 to 46: Cytological technique,
preconception, and the counting of human chromosomes. Bulletin of the
History of Medicine 48(4): 465-502.
 
Unger, L. and R. V. Blystone. 1996. Paradigm Lost: The Human
Chromosome Story. Bioscene: Journal of College Biology Teaching 22(2):
3-10.
 
Painter, T.S. 1971. Chromosomes and genes viewed from a perspective of
fifty years of research. L. J. Stadler Memorial Symposia (University of
Missouri Press) 1: 1-34.
 
Painter, T.S. 1923. Studies in mammalian spermatogenesis. II. The
spermatogenesis of man. Journal of Experimental Zoology 37: 291-321.
In this article Painter worries whether blacks have the same chromosome
number as whites. Talk about misconceptions. The number 48 is
introduced in this piece.
 
Painter, T.S. 1921. Y chromosome in mammals. Science 53: 503-504.
In this paper Painter hints at the number 46.
 
Tjio, J. H. and A. Levan. 1956. The chromosome number of man.
Hereditas 42: 1-6.
This is the paper that introduces the number 46.
 
Hsu, T.C. 1952> Mammalian chromosomes in vitro. I. The karyotype of
man. The Journal of Heredity 43: 167-172.
The lull before the storm.
 
Blystone in Texas
 
--------------------------------
Robert V. Blystone, Ph.D.
rblyston@trinity.edu
 
Department of Biology
Trinity University
715 Stadium Drive
San Antonio, Texas 78212
210.736-7243 FAX 210/736-7229
 
 
To the group:
 
In the words of Albert Levan in a paper titled: "How Man Got 46
Chromosomes." Levan was one of the authors of the landmark 1956 paper.
Dr. Levan communicated the paper to me Oct. 9, 1996.
 
"The determination of the correct number came as an inevitable
consequence of the methodologic improvements in the preparation of
mammalian chromosomes, introduced during the first few years of the
1950s. ... The first mammalian material in which the squash method became
an instant success was a specific kind of malignant cells, viz. ascitic
cells.... the first 'modern' analyses of mammalian chromosomes were
performed in 1951 by Makino in ascities cells of a rat tumor, and by
Hauschka and myself in ascites cells of various mouse tumors....These
difficulties were, however, gradually overcome thanks to the introduction
of two new technical procedures, viz, pretreatment of the cells with
colchicine, and expanding them with hypotonic salt solutions or
water....T.C. Hsu has told how he discoverd the 'miraculous' effects of
hypotonicity by a fortunate chance: Some slides had mistakenly been
rinsed in hypotonic instead of physiologic salt solution!....It turned
out that combination of the two treatments, colchicine and hypotonic, was
what meant the decisive step ahead. This combination of pretreatments
was tried out in the laboratory of John J. Biesele at the Sloan-Kettering
Institute for Cancer Research in New York....According to my experimental
records I received on June 22nd from Dr. Alice E. Moore at the
Sloan-Kettering Institute cultures of a human epithelial tumor,
HEp2....The first experiment I made was without any pretreatment... John
Biesele cried out: 'What a mess! This certainly is a case for the Hsu
hypotonoic treatment!!'....After my return to Lund, ....my collaborator
since many years, Joe Hin Tjio, happened to be at our lab at the time,
...we set up primary cultures of 4 human embryos....and gained
indubitable evidence that all 4 had 46 chromosomes."
 
Blystone in Texas
 
--------------------------------
Robert V. Blystone, Ph.D.
rblyston@trinity.edu
 
Department of Biology
Trinity University
715 Stadium Drive
San Antonio, Texas 78212
210.736-7243 FAX 210/736-7229
 
 
 
 
How about the belief that only proteins have catalytic activities? Until
Cech and Altman discovered self-splicing, catalytic RNAs. Kind of
fundamentally changed our theories abuout the chemical origins of life.
 
Rick
 
RICHARD P. HERSHBERGER, PH.D.
* Asst. Prof. of Biology * CARLOW COLLEGE * Pittsburgh PA 15213
rhershberger@carlow.edu * http://www.carlow.edu/~rhershberger/
* rhershberger@earthlink.net * http://www.earthlink.net/~rhershberger/
 
 
The November 3, 1994 issue of Nature has a big section called Frontiers of
Ignorance that includes many of the examples of ideas-no-longer-accepted we have
been talking about.
 
Many thanks to Robert Blystone for his insights on the 46/48 chromosome story,
which I will add to my book.
 
I'm doing a few articles on RNA for The Scientist. Does anyone have any opinions
about the best ways to extract and purify RNA? I'm going to interview Stanley
Miller next week -- a man who I think influenced many of us. Many thanks,
Ricki Lewis (76715.3517@compuserve.com)
 
 
Stanley Miller was interviewd on the Access Excellence Web site
(sponsored by Genentech).
 
You can check it out at http://www.gene.com/ae
 
Mark Stephansky
Science Dept. Chairperson
Whitman-Hanson Regional High School
600 Franklin St.
Whitman, MA 02382
617/447-7020 Ext. 41
Fax: 617/447-7099
 
How about the change in attitude toward fever? -from the
bring-it-down-no-matter-what approach of my childhood to more tolerant
treatment based on recognition that fever may be an adaptive
response--really a shift from thinking of fever as pathology to thinking of
it as healing.
 
Maren H. Brown, Ph.D. brownm@goliath.sunyocc.edu
Professor of Biology office (315) 469-2405
Onondaga Community College fax (315) 469-2593
Syracuse NY 13215
 
 
One more to add to the list:
Human sperm contained the tiny human. The egg was for nourishment only.
 
Linda Collins
University of Tennessee at Chattanooga
 
 
Pre-Hubble "there is only one galaxy, our own Milky Way"
 
Pre-Galileo "heavier objects fall faster" (Aristotle)
 
Pre-Galileo "the moon is as smooth and polished as a looking glass" (Aristotle)
 
Pre-Goddard 'Goddard lacks the common sense of even a school boy'... '
space travel via rockets is impossible' (the New York Times commenting on
Goddards experiments in liquid fuel rocketry)
 
"Heavier-than-air flight is impossible" (European ballonists of 18th &
19th century)
 
(misconception) Rockets push against the ground in order to take off
 
"humans will never break the 4 minute mile" (don't recall source, but Roger
Bannister did break the barrier decades ago)
 
"the human being is preformed in the head of sperm cell" (humunculists)
 
Information is 'sent' from each organ of the body to the sex cells via
"gemmules" in order to form a collection of traits to be passed on to the
next generation. (pre-Mendelian view on inheritance, held by even Charles
Darwin)
 
The human heart is the "seat" of intelligence (Notion held since the Greeks
until the work of Harvey)
 
John Banister-Marx
 

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