From: rowe@pender.ee.upenn.edu (Mickey Rowe)
Newsgroups: talk.origins
Subject: Re: More on three and four chamber hearts
Date: 10 Apr 92 21:37:03 GMT
Reply-To: rowe@pender.ee.upenn.edu (Mickey Rowe)
Organization: University of Pennsylvania

In article <1992Apr9.050422.21424@usenet.ins.cwru.edu>
      bk186@cleveland.Freenet.Edu (Julie Thomas) writes:

>I have often found that the more I learn about biology, the more 
>easier it becomes to become skeptical of evolution.  

Sounds to me like a confirmation bias...

> The standard line about increased efficiency 
>(meaning evolution works to increase efficiency?) didn't hold up to 
>scrutiny (as far as yours truly was concerned).  

What "standard line" is this?  Perhaps you're familiar with a more
conventional (perhaps more boring) claim that natural selection
expresses itself as differential reproductive success.  There is no
"goal" involved.  Efficiency of structure often results in a higher
reproductive success, but it is *not* something that evolution "aims"
to achieve.  Does that help any?

>If you look at these figures, it becomes quite obvious that the ol' 
>"complete the septum" story just won't work.  For if the reptilian 
>septum was completed, this would kill the reptile since the blood 
>from BOTH the right and left atrium could not enter the right 
>ventricle, thus it could not be oxygenated by the lungs.  

In the first place I'd like to state an objection to a fallacy that
you have either fallen for, or at least have not been cognizant enough
of to be more careful in your wording.  Modern reptiles are our
cousins, not our ancestors.  While it may be correct that at some
point in time our ancestor's had hearts with plumbing like that of
modern reptiles, you shouldn't begin by trying to draw structural
intermediates in a sequence from one modern group to the next.  It's
like having two people drive across the country--one drives from LA to
New York, and the other drives from LA to Palm Beach.  It's erroneous
to say that the person in Palm beach  must have driven through
Washington DC just because that point is intermediate to the current
positions of the drivers.

In the second place, where did "complete the septum" come from?  Are
you arguing against an explanation previously in the literature, or
your own first guess?  (I honestly don't know what others have written
on the subject, but I suspect you're concocting a straw person).

>But let's also look at interesting developmental consideration.  In 
>humans, when the interventricular septum is completed in about 3 
>months gestational age, the atrial septum still possesses a 
>discontinuity where there is cross-talk between the two atria. 
> Thus, development does not show a "2 complete atrial chambers /1 
>ventricular chamber --> 2 complete atrial chambers/2 compete 
>ventricular chambers" transition which is what was supposed to 
>have happened in the reptile heart to mammal heart transformation. 
>
>
>~It always seems that if we find a similar pattern in embryological 
>development, we are supposed to have evidence for evolution.  

Similar to what?  I don't understand what it is that you're talking
about here (though it smacks of recapitulation... if that is what
you're getting at, I suggest that you carefully read Bruce's latest
contributions to this thread).

>But if the
>pattern differs, well........     Evolution can be such a paradigm!  :)

Again, differs from what?  

Mickey Rowe     (rowe@pender.ee.upenn.edu)
Xref: sparky talk.origins:4154 talk.religion.misc:6420