the Origin of Life)
by Loren Haarsma, Ph.D.
and Terry Gray, Ph.D.
This page contains excerpts from pages 297 and 307-308 of Chapter 9 (Complexity, Self-Organization, and Design) in Perspectives on an Evolving Creation:
Is it possible
that simple organic molecules could self-organize into a living, reproducing
organism? Given our current scientific understanding, it is far too
premature to definitely answer either
yes or no. There are many hypotheses for how first life might self-assemble
on the early earth. All of these hypotheses are still speculative. The
most widely accepted hypothesis is a multistep process something like this: First,
in the right environment (hypotheses include underwater thermal vents, shallow
surface ponds, sandy beaches, volcanic craters, clay deposits, and weathered
feldspar), simple organic molecules concentrated and self-assembled into strings
of nucleic and amino acids (RNA and proteins). Second, when enough of these
molecules were concentrated together, they formed an interacting auto-catalytic
system that jointly catalyzed their mutual reproduction. Third, these RNA-and-protein
catalytic systems evolved, with RNA and eventually DNA taking on the role of
information storage, which we see in all living cells today. .....
Life is a complex web of interactions where proteins are required for nucleic acid synthesis and nucleic acids are required for protein synthesis. Similarly, the metabolites that fuel it are the synthetic precursors for protein and nucleic acid synthesis, yet they require proteins for their own synthesis. Origin of life investigators have had a difficult time envisioning a proteins-only solution. The RNA world scenario has fared somewhat better, but it is not clear how proteins get integrated. The replicating closed auto-catalytic system described by Stuart A. Kaufmann has the advantage that the complex web of interactions is built in from the outset. In essence this view acknowledges irreducible complexity, that is, the system has to be sufficiently complex in order for auto-catalytic behavior to emerge. There is no stepwise evolution of this emergent property; it suddenly appears (as with all emergent properties) once the polymer complexity has achieved the threshold level. Thus, the system is complex and whole from the start. Indeed, this is what living systems appear to be.
Here is the footnote on page 297:
Stuart Kaufmann (The
Origins of Order: Self-Organization and Selection in Evolution, p. 285)
writes, "...this new view, which is based on the
discovery of an expected phase transition from a collection of polymers which
do not reproduce themselves
to a slightly more complex collection of polymers which do jointly catalyze
their own reproduction. In this theory of the origin of life, it is
not necessary that any molecule reproduce itself. Rather, a collection
of molecules has the property that the last step in the formation of each
is catalyzed by some molecule in the system. The phase transition occurs
when some critical complexity level of molecular diversity is surpassed. At
that critical level, the ratio of reactions among the polymers to the number
of polymers in the system passes a critical value, and a connected web of
catalyzed reactions linking the polymers arises and spans the molecular species
system. This web constitutes the crystallization of catalytic closure
such that the system of polymers becomes collectively self reproducing. ...
[this new body of theory] is also robust in leading to a fundamental new
conclusion: molecular systems, in principle, can both reproduce and evolve
a genome in the familiar sense of a template-replicating molecular species."
Copyright © 2003 by Wm. B. Eerdmans Publishing Co.
(Grand Rapids, Michigan, USA), all rights reserved.
Haarsma & Gray (from same chapter) about Theistic Evolution
MORE ABOUT ABIOGENESIS (by other authors)
this page is http://www.asa3.org/ASA/education/origins/cheme-lhtg.htm