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Age of Earth and Origins of Life

John Logsdon jlogsdon at sunflower.bio.indiana.edu
Tue Jul 28 11:49:45 EST 1992

The following is a modified duplication  of a post that I intended to cross-post
to talk.origins AND bionet.molbio.evolution, but somehow it  never made it to
the latter.

Alright, here's a question for you geologists out there.
Young earth creationists, please do not bother.
PLEASE educate this molecular evolutionary biologist.

I am wondering; what serious values have been proposed for the age of earth?
In casual converstion, I usually hear values ca. 4.5 Billion years.
In a quick check of a few paleobotany texts (all I have at my immediate
disposal) this is close to what they cite in their "geological columns." 
In a nutshell,on which isotopes are these based and what statistical errors 
correspond to these measures? 

In a recent paper in  _Science_ (v257: 232-235, 10 July 1992), the authors
claim to have found fossil eukaryotic algae that are ca. 2.1 BY old. This 
is striking to me because this lineage likely represents a fairly derived
eukaryotic lineage itself.  In other words, there are a number of eukaryote
lineages which branched off before this one did.  This makes these other euks
older than 2.1 BY.  In fact, Archaezoa (euks with out mitochondria, ie:
_Giardia_, that wonderful intestinal parasite) are probably MUCH older than 
the Algae they found (_Grypania_).  Given this and that the root of the 
tree of life is EVEN DEEPER (between eubacteria and 
archaebacteria+eukaryotes), this seems to put "life" (ie: the common ancestor 
of all life: the "progenote") fairly ancient, perhaps ca. 3.5 BYA.  

This, as I read it, apparent ca. ONE billion year gap between the Earth's
origin and the origin of life is the impetus of this post. From a VERY
naive point of view, this doesn't seem very long. If in fact there
is significant statistical error associated with the Age of the Earth, or the
Dating of the fossils in question for that matter, perhaps there is a longer
time period between the Earth origin and Life origin. If not, are there any
problems with such an apparently limited time frame for evolution of life

Any primary literature (biology) and/or review/popular (geology) references 
are much appreciated.



John Logsdon         Department of Biology
                     Indiana University
                     Bloomington, IN  47405
                     (812) 855-2549
                     (812) 855-6705 fax

jlogsdon at sunflower.bio.indiana.edu


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