From: bk186@cleveland.Freenet.Edu (Julie Thomas)
Subject: From the heart!
Reply-To: bk186@cleveland.Freenet.Edu (Julie Thomas)
Organization: Case Western Reserve University, Cleveland, OH (USA)
Date: Wed, 15 Apr 92 04:36:06 GMT


In an attempt to cut down on mutiple requoting, let me simply 
respond to Bruce Salem's last post on heart development where he 
responds to me.  I encourage all readers to read that post (entitled 
"More on three and four chamber hearts") to insure that I have not 
taken anything out of context.


Bruce's primary complaint is that I am not offering an alternative to 
evolution.  He asks (more than a half-dozen times) for my 
alternative.  In fact, he goes so far as to suggest that my failure to 
provide an alternative counts heavily against my skepticism and in 
fact, might suggest a bias.  Let me quote him:

"  Which is all fine, be a skeptic, say that people are
constructing "just so" stories, but the real proof of your
pudding is for you to offer something better. Find something
that fills in the voids that can be tested, that tells how
to look for new and decisive evidence, and then get it and
present it to us with your arguments. Until then you are
just a naysayer, and as many people are reacting to the
ideas behind evolution from emotion and bias, that unless
you can build something constructive with your objections,
you too are subject to the question of bias".  

Let me make some observations.

1.  Bruce seems to be confused about the burden of proof here.  Bruce 
maintains that the heart evolved and I suppose he considers this to 
be a scientific truth.  Now I am not saying that the heart did NOT 
evolve.  I am not asserting any negative statement.  I have no 
"evolution belief".  That is, I am simply agnostic on this topic and 
have no alternative.  Bruce is making a postive assertion, I am 
making no assertion.  I simply question, and find myself increasingly 
skeptical of these evolutionary tales.  

In short, I don't need an alternative.  If I find the case for evolving 
hearts to be plagued with problems and lacking sufficient evidence 
for the belief, I tend to reject the belief even without an 
alternative.  Just because I lack an alternative does not mean I 
should turn a blind eye to all the problems in the popular story!  
Bruce on the other hand thinks hearts have evolved, and I'm sure he 
thinks this is a scientific belief.  He needs the evidence, and this 
belief is not supported by my lack of an alternative.

Furthermore, this whole approach seems quite similar to a common 
accusation against the creationsists.  They are often criticized 
because they think that by critiquing evolution, their beliefs will be 
vindicated.  The notion that one should accept evolution because it is 
the best we have seems very similar to this creationist tactic.  

2.  Bruce says that unless I "can build something constructive with 
your objections, <I> too <am> subject to the question of bias".  I fail 
to see how a lack of a theory suggests bias.  I have often found that 
it is the possession of some 'pet' theory which contributes to bias.  


Now to points of more substance (evolving from third to first person 
response, hopefully a beneficial mutation).  .

Bruce notes that "because there was no fossil record on this <the 
three to four heart transition> that we would have to use 
developmental sequences as the clues.  Despite problems with the 
idea of recapitulation in ontogeny of the phylogeny, the 
developmental anatomy is a clue to the phylogeny".  


Well, how do you know that developmental anatomy is indeed a clue 
to phylogeny?  Are you assuming phylogeny to uncover phylogeny? 
This approach seems circular to me.  And as I noted before, this 
whole approach is stacked so that only "evidence" for evolution is 
considered significant.   

I noted that your description of the developing human heart indicates 
it is quite different from the fish heart.  You responded:

"      So? I didn't assert that the fish hearts, remember
these are modern Teliosts, are direct ancestores. Do you know
how the Placaderm heart was constructed? What about sharks?"


Here is another example of evolutionary card stacking.  If 
differences are found that seem to be significant, it's time to wave 
the hands and complain about "modern fish are not the ancestors".
Fine, but then why are similarities in thse same organisms allowed 
to be evidence of evolution and are not subject to the same 
criticism?  The whole situation is set up so that all we are allowed 
to glean from these cousin relationships is evidence for evolution.
When significant differences are found we are reminded that we are 
comparing cousins, and all the ad hoc stories begin to follow to 
explain away the significance of these differences.  

I'm glad you brought up sharks.  If we consider the developing 
vascular circuit of vetebrates, sharks share a feature with reptiles, 
birds, and mammals, which is not shared by other fish and 
amphibians.  Namely, in fish and amphibians, the yolk sac is suppiled 
by blood from the systemic veins, while in Sharks and Co. the yolk 
sac is supplied by branches from the dorsal aorta.  Whether or not 
this is significant, the fact remains that here we have a similarity 
which is not due to descent.  This simply means that similarity NEED 
NOT imply relationship.  And if this is true, how can we trust the 
similarities of the mammalian heart and reptilian heart as 
demonstrating relationship?  



Now I questioned the significance of your description of heart 
development in mammals as far as the three to four chamber 
trnasition was concerned.  I noted:

"How does this help the reptile to mammal heart transformation?
Recall that in the reptile (with a three chambered heart) both
atria enter into the left ventricle.  What you need is the two
atria dumping into the left ventricle, then the right one shifting
to the right as the intervenricular septum completes it's growth.
The funny thing is that when it does, there remains an opening
between atria.  


You replied (*):

        *Why? 

Silly me.  You are suggesting that development provides "clues" to 
the supposed transformation, and I just noted that the type of 
transformation is not reflected in development.  So where is the 
"clue"?


*The original stipulation you made was how to
incorporate the pulmonary circulation while splitting the
ventricles. 

Yes, but I have learned more about hearts and development since then 
and am arguing what I consider to be a more significant point.  But 
even considering this point, I still don't see how this could have 
occurred in evolution.  Comparing a forming heart to a transition 
between two formed hearts might be a faulty analogy.


*If the developemnt is to be taken as a guide,
it suggests that the pulmonery circulation may have been
established before the ventricle got split. 

Yes, but why is development only taken as a guide when it supports 
an evolutionary notion?  For example, Drosophila and the mouse 
develop by radically different pathways.  If development is to be 
taken as a guide, it suggest that these two organisms are not 
evolutionarily related.  


The development
shows the that artium of the old three chambered plan becomes
the left atrium, and that the right atrium forms from the
bulbus and part of the ventricle in the arterial end of the
heart. The development of duel atria is well established and
takes place at the same time the ventricle is divided by its
septum.


Tomorrow, I'll try to post some more detailed considerations 
concerning the developing heart and it's purported relationship to 
evolution.


Oh, one more thing.  Let me go back to a statement of Bruce's:

"  Which is all fine, be a skeptic, say that people are
constructing "just so" stories, but the real proof of your
pudding is for you to offer something better. Find something
that fills in the voids that can be tested, that tells how
to look for new and decisive evidence, and then get it and
present it to us with your arguments."

Bruce, are you suggesting that we can test this notion that hearts 
evolved?  How so?  What new and decisive evidence does this belief 
about evloving hearts entail?  Why not present it "with your 
arguments"?  If you can't do any of this, why am I supposed to?

Xref: sparky talk.origins:4214 sci.skeptic:7990 talk.religion.misc:6643