Hi

I was wondering if I could hear from those who support the methodology
involved in 'Classical Twin Studies', where the desease in question is
known to have environmental correlates.

In the Classical Twin Study method MZ twins raised together in one
family are compared to DZ twins raised together in another family to
determine the influence of genetics on visible occurance of the
desease. In the Classical method it is assumed that identical twins are
no differently treated than none identical twins. This assumption is
called the Equal Environment Assumption.

This assumption has been questioned scientifically. The following link
has a discussion on this subject under the section "Comparing
monozygotic and dizygotic twins"

http://www.net4dem.org/cyrev/archive/Misc.%20Articles/IQ/IQandGenetics1.htm

These twin studies are used because MZ twins who have been reliably
known to be raised separately are not known of in sufficient numbers to
make ****ysis meaningful.

How meaningful can a twin study be when environment is known to
influence the Desease being studied?

Could more be learnt about deseases by looking instead at the most
discordant twins who show the least genetic influences upon the
desease? Should in fact this study be a prerequisite of any
meaningful Twin study where twins are raised together?

Thanks

Andrew

anon.

You would be better asking people working in genetic epidemiology - they
are the ones who use these studies.

Be warned: it looks like the writer has a political rather than
scientific agenda. I find most of his argument un-convincing: the only
bit I'd be worried about is the work of Spitz & Carlier. Unfortunately,
this is in French - Google translates the title as "The method of the
twins of 1875 has our days"!

Very - the whole point of twin studies is that they control for the
environment, as it should be the same for both twins. Problem can arise
if there are genotype by environment interactions, which is what the
author of the website is trying to claim.

There may well be problems with twin studies, but I would suggest you
examine the medical genetics literature. If there's something generally
wrong with them, it will be pointed out there (where there is less at
stake politically).

Bob

--
Bob O'Hara
Department of Mathematics and Statistics
P.O. Box 68 (Gustaf Hällströmin katu 2b)
FIN-00014 University of Helsinki
Finland

Telephone: +358-9-191 51479
Mobile: +358 50 599 0540
Fax: +358-9-191 51400
WWW: http://www.RNI.Helsinki.FI/~boh/
Journal of Negative Results - EEB: http://www.jnr-eeb.org

Each division of science has its biases. Vested interests are not
just the domain of huge corporations. How many valid studies dont get
done because it affects the authors reputation or ability to publish or
get funding? People who actually use these studies may be the people
to **not** ask. Then again it would be interesting to hear their
point of view it is true.

I find that surprising. Its easy to observe that Identical twins have
a special relationship that is unlike any other family relationship.
There 'environment' cannot be the same as those who do not have that
relationship. Twin study authors who ignore such a relationship need
to say why such a relationship is irrelevant to their results.

It means "Twin study methods since 1875 to the present day"

as you can see Carlier appears to have a respectable academic record
http://www.up.univ-mrs.fr/wpsycle/membres/enseignants/carlier.html

Academics involved in this work are under the same pressures to get
results as anybody else is. Those who wish to criticise fundamental
assumptions can often be harshly treated and only those who can
understand the studies in depth and have a vested interest in their
knowledge of those studies are likely to be in a position to make an
intelligent judgement upon them. That kind of perpetuates assumptions
rather than creates good science. Those who critisise are likely to be
judged reactionaries and so forth regardless of their academic
credentials.

For example you have portrayed Jon Beckwith, American Cancer
Society Research Professor, Harvard Medical School, Department of
Microbiology and Molecular Genetics as a person who warrants the label
"Be warned: it looks like the writer has a political rather than
scientific agenda" only because he has chosen to align himself with
scientists who want to challenge fundamental thinking.

Andrew

anon.

Who else would you ask? Someone who doesn't know the studies, and hence
hasn't had to deal with any problems associated with them?
<snip>

I suspect you know little of the history of the group Beckwith is
aligned with. They do have an ******** political agenda. Now, it may
be that he has raised some good scientific points that deserve
answering, but I think one should be cautious, and at the very least
hear from the other side, and examine both sides critically.

Bob

--
Bob O'Hara
Department of Mathematics and Statistics
P.O. Box 68 (Gustaf Hällströmin katu 2b)
FIN-00014 University of Helsinki
Finland

Telephone: +358-9-191 51479
Mobile: +358 50 599 0540
Fax: +358-9-191 51400
WWW: http://www.RNI.Helsinki.FI/~boh/
Journal of Negative Results - EEB: http://www.jnr-eeb.org

Bill Morse said


hence
hasn't had to deal with any problems associated with them?

The problem with these studies is that people see them published and
draw conclusions that good science was used. Meanwhile the group
continues its work grateful for the publicity and sponsor satisfaction
and so forth.

In the case of the example discussed elsewhere on this list where the
nurturists say the issue is 'Dominant mothers and absent/ineffectual
fathers" as contributing factor in male homo***uality an argument that
twin studies can settle the issue while **ignoring** differences in the
family dynamics of the twins cannot be reasonably expected to settle
anything at all - for those who are aware of the none genetic argument.


aligned with. They do have an ******** political agenda. Now, it may
be that he has raised some good scientific points that deserve
answering, but I think one should be cautious, and at the very least
hear from the other side, and examine both sides critically.

Its a fair comment.

I have not heard of that group before.

To me the EEA already seemed flawed. I went looking for discussion
on the EEA and found only Beckwiths argument which i felt addressed the
issues quite well. So far I have not heard the argument that supports
the EEA which addresses my concerns. The EEA trivialises something
that is complex for the sake of statistical convenience.

Can you put forwards an argument that the way identical twins are
treated is similar to the way none identical twins are treated by
examining the issue critically? It is commonly known that identical
twins have a special relationship and because they are identical they
are very similarly treated compared to fraternal twins. These
environmental differences are ignored in twin studies because of the
EEA. A commonsense critical inspection of the EEA says its just a bad
assumption.

Any argument for the EEA which ignores the commonsense observations
about twins cannot surely be one that can be credible.

Andrew

I am not exactly sure what group you are referring to or why a persons
politics necessarily conflicts with their ability to produce scientific
work.

I would like to continue using that critique by Jon and I wrote to him
to get his permission to quote it in full.

The man is well known in the world of genetics.

The review for his latest book

Making Genes, Making Waves: A Social Activist in Science

appeared in the prestigious Nature magazine.

"In 1969, in the same week that his famous paper about the first
isolation of a gene appeared in Nature (224, 768-774), Beckwith
called a press conference aimed at raising public awareness of the
possible consequences of genetic manipulation."

re/journal/v420/n6914/full/420362a_fs.html%26content_filetype%3Dpdf+jon+beckw ith+new+scientist+genetics&hl=en
Especially in the context of this group this man seems like an
outstanding scientist whos opinion carries some weight.

Am I wrong to think otherwise?

Andrew

anon.

Science for the People. Read the comments in italics at the end of the
paper.

If you want to read some more about their activities (admittedly from a
personal viewpoint), then read this:
<http://www.lrainc.com/swtaboo/taboos/wilson01.html>

I must admit that I haven't heard of him. In fairness, this could be
because genetics is a large field, and I've been following different parts of it.


Oh, but they print all sorts of rubbish. :-)

I don't know - I don't know his reputation. It's perhaps worth pointing
out that Lewontin is also someone who's opinions should carry weight in
this group, but also has (had?) a political agenda.

It's clear to me that he wrote the article to criticise twin studies
(rather than give a neutral review), and my inference from that, and the
background to the web pages that it's appeared on, is that he has a
political agenda for doing so. Now, as it's clear what he's trying to
do, one should ask how well he does it. On my reading he fails to land
any killer blows, which suggests to me that his case is weak. In an
article like this an author would tend to accentuate the work that
supports their view, and ignore or downplay work that disagrees with it
(everyone does this to a greater or lesser extent, so I'm not accusing
him of anything improper. And if he is biased, at least we know what
direction he's biased in!). So my reaction was "if that's the best
evidence he's got for his view, it's not very strong". I was expecting
to see some specific data ********ly showing biases in the studies, but
most of the article is saying that there are a few other things that
might make a difference. Of course, they might not as well.

It may be that some of his criticisms are valid, but if so, then I would
expect that there has been some response to the article in the last 5
years, which may be more informative.

Bob

--
Bob O'Hara
Department of Mathematics and Statistics
P.O. Box 68 (Gustaf Hällströmin katu 2b)
FIN-00014 University of Helsinki
Finland

Telephone: +358-9-191 51479
Mobile: +358 50 599 0540
Fax: +358-9-191 51400
WWW: http://www.RNI.Helsinki.FI/~boh/
Journal of Negative Results - EEB: http://www.jnr-eeb.org

Bob

Several times now you have said that Jon Beckwiths critique is biased
and weak.

Not once have you critically evaluated the question for yourself and
shown your reasoning here on this list.

Instead you have apparently put up a smoke screen of chatter which has
avoided the thread and made it somebody elses responsibility to decide
on.

Whenever i have raised the issue of the EEA I have got a similar none
response.

It is beginning to appear there is no critically evaluated response to
criticisms of the EEA. Thats kind of convenient for those that argue
I cant rely on Beckwiths comments until I have found another argument
against what he has said.

Commonsense suggests the EEA is total nonsense. Identical twins cannot
be assumed to have equal psychological and behavioual environments in a
family to none identical twins. If that statement is weak then
please I beg you, please put forward your reasoning for that,
regardless of your other opinions about other subjects!


Andrew

anon.

No, I have critically evaluated it twice - I haven't given a detailed
critique because I didn't want to get into a long discussion that was
only tangentially on topic for this NG.


One should be careful about trusting "common sense". Humans are very
good at seeing patterns, even if they're not actually there. That's why
science can be difficult, because you have to be rigourous about showing
that the pattern exists. There is a danger that if one knows that twins
are identical, then one will tend to emphasise their similarities.

So, put your statistics on the table. If EEA is "total nonsense", then
give me the hard evidence to show that it is.

Bob

--
Bob O'Hara
Department of Mathematics and Statistics
P.O. Box 68 (Gustaf Hällströmin katu 2b)
FIN-00014 University of Helsinki
Finland

Telephone: +358-9-191 51479
Mobile: +358 50 599 0540
Fax: +358-9-191 51400
WWW: http://www.RNI.Helsinki.FI/~boh/
Journal of Negative Results - EEB: http://www.jnr-eeb.org

william morse

Granting your premise about a special relationship for the moment, are
you sure that the special relationship is an "environmental" factor?
Siblings who are not monozygotic but who happen to have inherited many of
the same genes also have a special relationship, let's call it the
"relatedness relationship". Dizygotic twins, even though they are
genetically quite different, have a special relationship due simply to
being of the same age (which can affect social factors) and sharing a
similar environment in the womb, let's call it the "DZ relationship". So
perhaps the special relationship of identical twins is simply a
combination of the environmental factors of shared age with the
similarity in thought, appearance and behavior caused by shared genetics,
i.e. the "MZ relationship" = "relatedness relationship" + "DZ
relationship". However, since the specialness of the relationship due to
similarity in thought, appearance and behavior - the "relatedness
relationship" - may be relatively unaffected by other environmental
factors, we can call this genetic. So in a comparison of MZ and DZ twins,
even though the MZ twins have a more special relationship than the DZ
twins, it could still be that the difference in relationship is almost
all "genetic" - in which case the equal environmental assumption is still
correct, i.e. traits that show more variance between DZ twins than
between MZ twins can be considered to be more due to genetics than to
environment. It's just that part of the "genetic" effect is due to
overall genetic similarity, rather than an identical allele at a
particular locus.

Yours,

Bill Morse