Time of divergence of prokaryotes

Arlin Stoltzfus arlin at is.dal.ca
Fri May 16 14:19:20 EST 1997


Martijn Huynen wrote:
> 
> Hi, I am looking for references that give the estimated "time of
> divergence"  of the presently completely sequenced (and publicly
> available) Bacteria and Methanococcus janaschii. (so not only between 

There are no reasonable biological data from which to estimate this-- 
macromolecular sequence data simply aren't sufficient to narrow 
the date significantly within the range of reasonable estimates 
allowed by fossils and geochemical evidence.  Archaebacteria and 
eubacteria could have diverged as early as 
4 BYA or as recently as just 2 BYA.  Some people argue that 
3.8-BY-old stromatolites represent members of the eubacterial group 
cyanobacteria, and that archaebacteria must have already been 
a distinct lineage at any point in time when the distinctive 
features of cyanobacteria had already arisen.  Personally I think 
this is a reasonable but somewhat risky argument.  I'm guessing 
that the answer is 3.5 +/- 0.5 BYA, but it might be safer to 
assume 3 +/- 1 BYA.  

I was very impressed with the computer model of RNA evolution 
described in your PNAS paper of last year as well as in a more 
recent paper.  Some of us here are trying in much less sophisticated 
ways to wrestle with the relationship between neutral evolution
and biological complexity.  Soon I will be submitting a manuscript 
about the possibility of constructive neutral evolution, a draft 
of which is available at my web site: 

  http://is.dal.ca/~arlin/cne

I would appreciate any comments you might have.  My approach to 
evolution is very much based on the biochemical details of specific 
life processes.  So far I have not tried to make any connections with 
systems theory, but I am interested in such connections, if they 
exist.  Regards,

Arlin

-- 
Arlin Stoltzfus, Ph.D.
Department of Biochemistry
Dalhousie University
Halifax, Nova Scotia B3H 4H7 CANADA
(email) arlin at is.dal.ca 
(phone) 902-494-2968 
(fax) 902-494-1355



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