what is life? my 5 cents

suter at VAX.MPIZ-KOELN.MPG.d400.de suter at VAX.MPIZ-KOELN.MPG.d400.de
Wed Feb 23 07:41:07 EST 1994


+In article <2k8bt7$nqb at usenet.INS.CWRU.Edu> ef949 at cleveland.Freenet.Edu 
+(Mark Petrie) writes:
  >To those who disagree with current "accepted" definitions of life
  >that relate to the following able to reproduce, metabolism etc
  >and then go on to say life cant be thought of in our terms
  >because there could possibly to non-nucleic acid life on another
  >planet, I say humbug! Scientific methodoligy is on provable
  >and duplicatable knowledge. Maybe provable is the wrong
  >word but you get the drift. I say we keep our definition
  >with the openness we should all have , that science is continualy
  >changing and being redifined as we learn more. 

to which sean eddy replied:

+On the contrary, scientific methodology is about what you imagine is
+possible and what you want to look for. When the next lander goes to
+Mars, I guess you'll send a PCR machine and universal ribosomal DNA
+primers?  And when it doesn't amplify anything except some NASA or ESA
+technician's fingerprints, you'll say, "nope, no life on Mars?"

the experiment you describe would never allow such a conclusion, simply
because you would never be sure whether you picked the right postion
on the planet's survice and so on. 
but if a nucleic acid would be detectable on Mars, and it could be shown 
that it has self replicating capability, i would conclude life is 
present on mars....

+There are real, though remote, possibilities of finding life or
+remnants of life elsewhere in this solar system within our lifetimes,

i doubt this already ! there is no indication what so ever that nucleic
acid based life, or any other form is present outside our planet. and
the presence of 'simple' carbon based molecules is no proof either.

+and it doesn't have to be DNA or RNA based.  It's pretty unlikely that
+a Martian would come up to a lander and wave at the camera -- though,
+as Viking did, it's wise to take a camera along just in case. We need
+a broad operational definition of life so we can design good Martian
+(Europan, Titanian, whatever) experiments.

naturally we should keep our eyes open for the unexpected. i will be the
first one to admit that our definition is not broad enough, if e.g. 
intelligent signals from outerspace would manifest itself completely 
independent of nucleic acids (this excludes computers, hehehe). but as long as
no one can show me a putative lifeform that does not adhere to the nucleic
acid definition, why should we broaden it ? computer viruses, extra-
terrestrials and chain letters, ok, it is funny to think about, and to look 
at them as lifeform imitations, but perhaps you could come
up with some arguments WHY they are alive (i didn't follow the discussion
completely, i am sorry. perhaps a summary would be timely ?).
   
cheers,
clemens
===============================================================================
Clemens Suter-Crazzolara, PhD
Max-Planck-Institut fuer Zuechtungsforschung
Abteilung Genetische Grundlagen der Zuechtungsforschung
Carl-von-Linne Weg 10,        D-50829 Koeln, Germany
Tel.xx49.221.5062-221    Fax.-213      e-mail: suter at vax.mpiz-koeln.mpg.d400.de
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