Theory of Evolution of Eukaryotes, Crossing Over, and Sex

James Howard jmhoward at sprynet.com
Sun Sep 21 17:41:20 EST 1997


Andrew J. Roger wrote:
> This is a long message. To offer criticism for the idea, I have chopped
> bits out (so that someone might actually read it)
> James Howard responds:
How convenient for your purposes that you omitted, essentially, my entire posted theory. You left in one 
"bit," that consisted of a little over four lines!  So, "to offer criticism for the idea," you chopped all of 
it, but four lines!

> James Howard wrote:
> >An increase in T-A bases would increase the effects of DHEA in
> > the host genome. I suggest this is the reason that E. coli has
> > approximately 25% of each of the nitrogenous bases, while humans and
> > other mammals have about 21% cytosine and quanine and 29% thymine and
> > adenine.

> Andrew Roger said:
> So humans and other mammals account for how much eukaryotic diversity?
> Eukaryotes probably evolved between 1-2 billion years ago. Mammals
> appeared ~200 mya.  If you want to cite evidence for a theory of
> the origin of eukaryotes, you should be concerned with features
> exhibited
> by all eukaryotes (for instance PROTISTS).  Base composition has
> changed many times in many different eukaryotic lineages....so a bias in
> mammals
> probably reflects nothing about the ancestral state of eukaryotes
> as a whole. Diplomonad flagellates, possibly one of the deepest
> eukaryotic
> branches, in general exhibit elevated G+C and lowered A+T.....this
> could equally be ancestral to eukaryotes!

James Howard responds:
If you had understood my reasoning, you should have understood that my explanation suggests that histones 
increased the survival of mitochondria in "host" cells.  I suggested that subsequent to that invasion (of 
mitochondrial-like organisms), the nuclear membrane evolved to sequester histones in the cell nucleus.  This 
should produce, over time, an increase in the percentage of thymine-adenine bases, and a decrease in 
percentage of guanine-cytosine bases.  I gave two examples of organisms that fit this prediction.  E. coli has 
probably not changed much in the billions of years, you mention, and humans are a recent product of evolution, 
at the end of billions of years.  

Now, just above you suggested that I should be concerned with protists.  Then you make your statement about 
diplomonad flagellates, i.e., "Diplomonad flagellates, possibly one of the deepest eukaryotic branches, in 
general exhibit elevated G+C and lowered A+T .....this could equally be ancestral to eukaryoties!"  Well, my 
theory suggests that the increase in percentage of A+T is the result of evolution.  Therefore, I suggest that 
lack of a mechanism that alters DNA toward increased percentage of A+T, represents a lack of evolution.  These 
organisms have not evolved much.  The existence of these organisms does not refute my theory of evolution of 
the eukaryotes.

Andrew Roger said:
> I am not sure if what you have come up with is a theory of the ORIGIN of
> eukaryotes...(perhaps this is not your intention).  Your theory is
> more correctly viewed as a theory of
> 
> a) selective forces that led to the establishment of mitochondria
> b) origin of crossing-over
> c) origin and evolution of sex
> 

> A theory about the ORIGIN of eukaryotes must at least explain
> the following:
> 
> a) the origin of the cytoskeleton (actin, myosin, tubulins, dynein,
> kinesin etc etc.)
> b) the origin of the endomembrane system
> c) the origin of the nucleus
> d) the origin of mitosis
> e) the origin of multiple linear chromosomes withe telomeres and
> multiple
>    origins of replication
> 
> It should probably also involve explanations of:
> 
> f) timing and origin of mitochondria
> g) timing and origin of karyogamy and meiosis
> h) timing and origin of eukaryotic flagella
> 
> So far your theory only deals with only 2 of these things....and is
> therefore not
> explaining the hardest things to explain about the origin of eukaryotes.
> 
> Incidentally, theories for the "chimaeric" origin of eukaryotes also
> suffer from ignoring most of the above problems.  And therefore they
> shouldn't be considered theories of this at all....rather theories
> for explaining the conflict between gene phylogenies.
> James Howard responds:
I suggest I have a good theory of the origin of eukaryotic organisms.  I suggest the items, which you define 
as necessary to explain the "origin" of eukaryoties, occurred subsequent to the events described by my theory. 
 I had hoped that someone may have understood, based on my explanation, that the increase in percentage of A+T 
bases implies that differentiation occurred.  This change in differentiation would account for the evolution 
of the cellular mechanisms, you require.  Therefore, to answer you, I suggest that, subsequent to the 
beginning of eukaryotic organisms, explained by my work, the items you require evolved in the billions of 
years of evolution.



More information about the Mol-evol mailing list