Re: The Great Filter
Thu, 22 Aug 1996 16:14:14 -0400 (Twirlip of Greymist) writes:
>On Aug 21, 2:55pm, wrote:

>} Actually the ribosome RNA sequences indicate eukaryotic and prokaryotic
>} are approximately equal in age. Eukaryotic life, with its hodgepodge of
>} interacting and varied systems and vast amounts of apparently useless
>} is a much more plausible model for spontaneous self-organization a la
>} Kauffman than efficient, minimized prokaryotic life.

>Um. I'm not an expert, but I'm not sure how useful rRNA is here. One
>model of eukarya is that a magnetobacterium swallowed an archaean and
>turned it into its nucleus, with similar swallowings for famously the
>mitochondria and chloroplasts.

Swallowing is a very reasonable model for origins of eukaryotes, but neither
the nucleus, with its linear chromosomes, nor the rest of the cell, with its
intricate cytoskeleton, is like any bacteria bopping around today. The lines
of the swallower and swallowee are probably extinct, regardless of whether
they were prokaryotes or something else.

> I mean, I know rRNA is used for the
>phylogenetic trees but I'm not sure how it would distinguish here. Also
>that there may be some assumptions of uniformity, and I'm not sure how
>robust the method is to some past deviation we couldn't see.

The robustness is not well-established but is suspected; eukaryotes have as
much variation in their rRNAs as prokaryotes. It should be very hard to
generate that much variation without an enormous amount of time.