Why only L amino acids?(Why not?)

ed beaty edbeaty at uxa.cso.uiuc.edu
Tue Jul 12 17:25:02 EST 1994

In article <1994Jul12.122345.1 at mcvax4.d48.lilly.com>,
dallas at mcvax4.d48.lilly.com wrote:
> I know much of the discussion has been on a serious note, but I tend to like
> the "We don't know" theory the best.  Why blow smoke?

Because it's about all we CAN do.  (Unless somebody has a Time Machine

> One thing I do like is that nature is parsimonious (thrifty for those without
> $.25).  At some point (much like when Moses(aka Mel Brooks) came down from the
> Mount and dropped one of THE THREE tablets), a choice was made.
> (see "History of the World-Part I")
> Other explanations:
> Life only existed in the Northern hemisphere( what was the structure of
> Gondwana Land?). Does life exist in the Southern hemisphere today?  A joke to
> my mates in Oz.

[Warning:  Smoke alert.  Wild speculation by an untrained git follows...]

Hmm.  Maybe it did!  One theory is that life evolved at the interface
between land and sea, in sometimes-dry, sometimes-wet pools of concentrated
muck.  If all (or most) of the land was in one hemisphere 4 billion years
ago, then those funky coriolis effects people've been talking about may
have something to do with it.  (And by hemisphere, it doesn't have to be
the North or South geographic poles...the magnetic poles have wandered
quite a bit since the Beginning, yes?)

> We all know the partiality of God to right-handers (if you think of the protein
> helix) and that 'left' in Latin is 'sinister'.  God also picked L-amino acids
> because he does have a sense of humor and likes to read a good discussion on
> the net.

Yeah, like God has nothing better to do than read the net.  As if!

> Now serious stuff but questions for thought.
> Was the beginning of life proteinaceous or nucleic acid in nature?  I thought
> it was AGREED to be proteinaceous.

Was it?  I'm not too current on the literature, but I believe it was
thought to be RNA-based for a long time, then RNA-protein based (primitive
ribosomes?) then DNA-RNA-protein based.  And there's the theory (by
Smith-Cairns) that crystalline "replicators" were the foundation on which
RNA life got its start.

My best theory: the earliest organisms were accidentally brought to earth
by time-traveling biologists from our future.  [Warning:  Paradox alert...]

ed beaty
edbeaty at uxa.cso.uiuc.edu

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