Susan Hogarth wrote:
>>higginss at VAX.CS.HSCSYR.EDU wrote:
> >
> >... Also, what extant
> > organism is considered the most ancient.
>> Could you explain what this means? On the surface, the question seems to
> be "What is the oldest thing still living?", but I suspect you mean
> something different...
I suppose it could mean: what living organism displays the most
retained ancestral features of the latest common ancestor of
all life? I think this could be a reasonable question. My
bet is that eubacteria, in general, probably are most similar
to the latest common ancestor of life in their overall cellular
architecture-- they prokaryotic cells with ester-linked fatty-acyl
lipids, with a circular chromosome and genes organised into
operons. It seems that the cenancestor (most recent common
ancestor) probably had all of these features if one accepts
the following tree:
Ester/Fatty-acyl Circ chromo Operons
_____ Eubacteria YES YES YES
/
---/ ___ Archaebacteria NO YES YES
\ /
\/
\
\___ Eukaryotes YES NO NO
Of course the overall similarity of an organism to an ancestor will
depend on what characters you choose to evaluate AND how you weight
the various characters.
Cheers
Andrew J. Roger
