Re: Cope's rule and bacterial evolution

I continue to think that the idea of a single LUCA (with only occasional
HGT since then and only a very few cases of endosymbiosis) is the most
fruitful hypothesis to drive research.

I respectfully disagree. IMO it's completely unknown at this time
whether the various highly-conserved genes we track across all three
domains co-evolved all the way back to a single LUCA or whether they
criss-crossed or otherwise followed different whole-cell trajectories
during the very early days. We should not pre-judge this question
and direct all our research as if it were true. Instead we should
draw evolutionary trees for each gene separately and then compare them
to see which co-evolved together how far back and where such
co-evolution ceases further back indicating a merging of those parts of
the genomes at that point. Then we can effectively consider evidence
for the very distant evolutionary history to judge how many different
early common ancestors yielded genes we can trace to the present day.

In fact, I doubt that complete fusion of genomes was particularly
important at any time since protein synthesis and the unpartitioned
cytoplasm.

Except for endosymbiosis where two or more complete genomes merged into
a single cell but remained in separate organelles within the cell, and
only later most/all of the genes from one organelle miagrated to
another, for example most of the mitochondrial DNA, and all of the
spindle DNA, right? I'm not claiming that two genomes ever instantly
merged into a single organelle. All I'm claiming is endosymbiosis as
above, with DNA only gradually miagrating from one location to another
within the cell, or direct horizontal-gene flow from one cell to
another completely different cell, where only a small amount of DNA
flows during any single event, but over hundreds of milions of years
most/all of the DNA could get copied from each single clade to most/all
of the other clades.

Well, I didn't notice any "hairbrained ideas" in this posting which
could make you famous. I've heard almost all of those ideas before.

Yeah, but when you heard them before, did you think those people with
those same ideas were crackpots who thought it was possible to build
perpetual motion devices and travel back in time to change history, or
did you think those people were bright kids who needed funding and a
thesis advisor so they could perhaps develop their ideas into actual
science?
..

.