A great many scenarios of the origin
of life (abiogenesis) have been proposed over the years. I
explore here specific features of an origin of life
developing on minerals, based on the idea that selective
steps are essential early on, and that metabolism
originating on minerals is poised to answer the riddle of
selection, as well as the need to make polymers
Following the consistency of the
reasoning of Freeman Dyson in his book Origins of Life,
I further show that reproduction of metabolism must have
predated replication of the genetic material and propose
that nucleotides were created by a leak of a nitrogen
fixation process. Furthermore homochirality is a false
problem as maintaining a mixture of stereoisomers would
cost much more information than spontaneous symmetry
breaking. Chirality is not a relevant question: On a road,
on must ride either on the left or on the right, not both.
The choice of the side of the road is often contingent:
the reason why continental Europe chose the right, is just
because Napoleon decided so! In the same way many
constraints operate that limit life based on the chemistry
The atoms that can be used to this
purpose are limited in number, and it is only sloppy
experiments and media hype that let some to think that
arsenic could be present in the backbone of nucleic
acids. At best it could be included as a
"decoration" of the standard phosphodiester backbone.
A further line of reasoning suggests
that, as in the evolution of human artefacts, things
tended to start big and awkward to progressively
miniaturize. In The
emergence of the first cells I propose of new
scenario, combining two types of RNA worlds:
Abstract The scenario proposed
here builds on the critical need for compartmentalisation
at the origin of life. In a first step, the surface of
minerals compartmentalised and selected the reactive
compounds that formed primitive metabolism. Subsequently,
RNA molecules replaced mineral surfaces after the
discovery of nitrogen fixation and the emergence of
ribonucleotides, in parallel with a machinery for
synthesis of peptides, coenzymes and lipids. Then, the
RNA-metabolism world developed into an RNA-genome world
based on RNA as informational templates rather than
substrates. Bordered by lipids, the first cells were
phagocytes, Protokarya, which put together two
compartments stemming from the RNA-metabolism world (the
cytoplasm) and the RNA-genome world (the nucleus).
Emergence of stable deoxyribonucleotides allowed the
clustering together of genes into chromosomes.
Phagocytosis created the opportunity for an escape based
on an alternative metabolism of membrane lipids and
conquest of extreme environments, with the Archaea, and on
the emergence of a robust and phagocyte-resistant
envelope, with the Bacteria. Reductive evolution allowed
bacteria with a modified enveloped to be phagocyted again
as symbionts of Protokarya, leading to the final
generation of the Eukarya. Continuation of horizontal
transfer of the genetic material initially resulting from
phagocytosis was carried on with the emergence of gene
transfer via specialised conjugation machineries and
viruses. DOI: 10.1002/3527600906.mcb.20130025
Lecture given in Rio de Janeiro
for the 100th Anniversary of the death of Louis Pasteur
Presentation of the
conference in Rio (in French, autumn 1994)
of the presentation
genomics of extant bacterial genomes unravels a
scenario of the origin of life (2007) we
substantiate some of the hypotheses proposed here. In
particular the idea that metabolism predated
template-mediated replication of nucleic acids becomes
an inevitable consequence of what we know of extant
life. This also emphasised the importance of
iron-sulphur clusters at the origin of central metabolic
pathways that must have predated life as we know it
today, and that are conserved in most living organisms,
sulfur atom at the very heart of life.
Louis Pasteur discovered that an original feature of
organic matter was associated to life: organic molecules
that derived from living processes were optically
dissymmetrical. In contrast, molecules obtained
artificially were symmetrical. Life had therefore to
include a specific process to be differentiated from the
usual chemistry. Added to his own philosophical (and
perhaps religious) convictions, this meant to him that it
was hardly conceivable that life could originate from
chemical matter, be it mineral or organic. Life had to
proceed from life. Because it was well known that broth
left standing in the air yielded a variety of clearly
living processes, it was necessary to think that this
corresponded to the pre-existence of living seeds that
could multiply in the broth:
« J'ai la
prétention de démontrer avec rigueur que dans toutes les
expériences où l'on a cru reconnaître l'existence de
générations spontanées, chez les êtres les plus
inférieurs, où le débat se trouve aujourd'hui relégué,
l'observateur a été victime d'illusions ou de causes
d'erreur qu'il n'a pas aperçues ou qu'il n'a pas su
éviter. » *
Because life is so sensitive to high temperature, it was
easy to destroy the seeds in the broth, and, with
appropriate technical constructions, to prevent
reinfection of the broth by living seeds: if this
hypothesis reflected truth, then a broth sterilised by
heat would be stable in time, and would not lead to the de
novo creation of life. In contrast, allowing the broth to
be open to the air - where seeds were supposed to be
present - would start the well-known multiplication
process. This created a difficulty raised by Pouchet who
showed that a boiled hay broth reaveled life after some
time. This was in fact caused by heat-resistant spores of
the bacterium Bacillus
subtilis (named the "hay bacterium" in many
languages). A further objection could be raised to this
approach if the living principle was immaterial (i.e. had
no weight permitting it to sediment into the broth): but
this could be tested by using vessels open to this
immaterial principle, where the opening could not permit a
material seed to reach the broth (this was the origin of
the famous Pasteur's "swan" shaped vials). This Pasteur
carried out, and started both a new conceptual theoretical
trend in the study of the origin of life, and an
industrial process, known as " pasteurisation ".
What is the situation today, and can we predict the
future trends of research in this domain of research? In
spite of the demonstration by Pasteur that no life emerged
from a broth, there is still a dominating model where a "
prebiotic soup " is the prerequisite for life's birth.
Many scientists have however stressed that life had rather
to start from a mineral environment, had we to propose
that it started on Earth. Among them, four major leaders
should be considered: Desmond Bernal, who pointed out the
importance of clays in mineral catalysis of organic matter
; Samuel Granick, who considered that photosynthesis
had to be created on a solid surface, and use sulphur
compounds as redox intermediates, and that we should
analyze extant metabolism to extrapolate back to the
origin ; Graham Cairns-Smith, who established clearly
that a prebiotic soup would be poisoned by its very
capacity to generate a large - much too large - variety of
organic compounds, and who proposed the existence of a
clay replicating material as predating our organic life
; and, more recently, Günter Wächtershäuser, who
insisted on the fact that metabolism, at the surface of
solid particles, should be seriously considered as the
only possibility for generating life as we know it today
I shall not here summarise the famous little book of
Schrödinger , nor endeavour to define the laws of life,
but place in the limelight four processes that must be
intimately associated in all living entities. They are:
metabolism, compartmentalisation, memory and manipulation
. The two former processes are organized by small
molecules (a few tens of atoms at most), whereas the two
latter are controlled by macromolecules (nucleic acids and
proteins), associated via processes that are considered as
information. Thus, two spatial scales are
intertwined in living processes, that develop at a
It has been thought to be so difficult to reconcile all
these processes together that a physicist like Freeman
Dyson has even proposed that life originated twice .
This explains why most molecular biologists have simply
forgotten to take into account metabolism and
compartmentalisation as questions posed to all models of
the origin of life, and have only considered proteins and
nucleic acids. In recent years, the concept of "chassis"
proposed by Synthetic Biology, is remarkably adapted to
take into account both processes. At the conceptual level
also, when comparisons have been made between life and
Turing machines, the general principles for the
construction of a self-replicating machine (the chassis)
have nearly always overlooked the need for
compartmentalisation and metabolism.
In contrast - and this should come out as a surprising
conceptual defect in scientific thought - scientists get
often very excited when one discovers yet another organic
molecule in the cosmos, be it only an amino-acid, as if
this gave us a clue for the origin of life! Following
another trend the recent discovery of ribozymes  has
been perceived as allowing us to solve the famous vicious
circle, who is the first, the chicken or the egg, nucleic
acids or proteins ? As a consequence life is now seen
as having originated in an " RNA world " endowed of the
metabolic functions that are displayed today by protein
enzymes. In this context it is amusing to illustrate the
scientific debate by two quotations expressing the most
opposite views. In an argument similar to that of
Cairns-Smith in his Genetic Takeover, Steven
Benner for example wrote « arguments that attempt to
extrapolate from modern biochemistry back to the origin
of life are futile », , whereas Wächtershäuser
described his own approach  as « a reconstruction
of precursor pathways by retrodiction from extant
pathways », as was proposed by Granick**
in a scenario inspired by photosynthesis . While the
former hypothesis makes that it is more or less impossible
to guess what happened at the origin, the latter can be
used as a heuristic approach. Of course we do no know
which is right, and it is likely that the present
metabolism is both an archive and a palimpsest. A major
question remains however, for all models involving an RNA
world, that of the origin of nucleotides, and - this is
not of minor importance either - that of the origin of
membranes. This places us back to the question of
metabolism, and to another chicken and egg paradox: which
is the first, RNA or small precursors? Granick's and
Wächtershäuser's models are meant to solve this issue, by
placing metabolism of small molecules at the origin, using
the selective power of solid surfaces, this, without
requiring as Cairns-Smith did, the need for an ancestral
mineral genetic replication process.
The important line of reasoning when thinking about life
is to consider two main processes, reproduction of
the cell machinery, with its compartments (what synthetic
biologists name the chassis) and its metabolism, and replication
of the genetic program. In his book Origins of Life, Dyson
has convincingly shown that this means that in any
scenario of origins, reproduction must have predated
replication. In Synthetic Biology efforts most
investigators are interested in the program, not in the
machine. Yet efforts by some, such as Doron Lancet or Pier
Luigi Luisi, aim at understanding the reproduction phase,
by constructing mathematical and experimental models of
what could have happened in the past.
In a nutshell, the model can be summarised as follows.
Appropriate mineral surfaces, carrying an excess of
positive charges, can select from an aqueous environment
molecules that are negatively charged, mainly
polycarboxylates and phosphates. These molecules are able
to react together, and only those that are able to bind on
the surface are kept for further chemical evolution. In
this model, entropy-driven processes are important
because, on a surface, they favour polymerisation,
especially when it is caused by elimination of a water
molecule (this is what usually happens in biological
polymerisation) [4,11]. Here too, the model goes against
the popular trend, the entropy rise being the positive
element that creates the order necessary for life
Extant metabolism allows one to substantiate the model
by identifying clues for the first steps of a surface
metabolism, stressing the importance of a few
autocatalytic steps (because they provide a
self-consistent means to stabilise the synthesis of those
molecules that are further metabolised). In this model,
coenzymes and nucleotides - molecules usually overlooked
by scientists working on the origin of life - are of prime
importance. The core of metabolism is made of
triose-phosphates , and energy is derived from iron and
sulphur redox transitions, leading to formation of a solid
which has iron-sulphur clusters at its core, pyrite .
At this point it is necessary to investigate further the
fate of solid particles: organic molecular species must
have substituted for them. Cairns-Smith has proposed that
RNA molecules, as polyelectrolytes that could mimic clays,
are the obvious substitutes of surfaces . Is it
possible to find in present day RNA molecules, a class
that could have played such a role? In 1975, Wong (now at
the Hong Kong University of Science and Technology),
describing the structure of a possible universal genetic
code, proposed that transfer RNA molecules have played the
role of a rigid holder allowing for local modification of
substrates . Since then, many examples of metabolic
alterations involving transfer RNA have been discovered
I have proposed to name homeotopic transformation the in
situ modification of non nucleotide residues carried by
tRNA molecules. This accounts for the fact that different
chemical groups can often be used to modify a given
position of the molecule held by the tRNA molecule.
Several examples illustrate this process: amidation of
glutamic acid on tRNAgln, first described by
Wilcox and Nirenberg , and also found in chloroplasts
, and addition of hydrogen selenide on an activated
tRNASecys, charged with activated serine for
synthesis of proteins containing selenocysteine both in
eukaryotes and prokaryotes [16-18]. Another well-known
example of homeotopic transformation is the formylation of
methionine carried by initiator tRNA in prokaryotes. This
illustrates the involvement of intermediary metabolism in
the control of macromolecular syntheses, as expected if
metabolism is historically intimately associated with
translation processes (see below) . Finally, tRNA is
also associated with many other metabolic processes that
are not related to translation. For example it has been
observed that charged lysine tRNA is involved in the
synthesis of lipids , or that charged glutamic tRNA is
necessary for synthesis of the heme precursor
aminolevulinate in chloroplasts and in many bacteria
Remarkably, charged tRNA molecules can also be required
in reactions involving peptide bond formation in the
absence of ribosomes. This is the case of synthesis of
cell wall peptides in Staphylococci or Micrococci where
tRNAser, tRNAthr or tRNAgly
are involved [27-30]. N-modification of proteins by
addition of leucine or phenylalanine residues has also
been demonstrated in Escherichia coli [31,32].
Finally, degradation of ubiquitylated proteins requires,
at least in some cases, the addition of arginine residues
provided by charged tRNAarg [33-35].
added 15th october 2005: the
work of Dieter Söll is strongly substantiating this
Note added 23d february 2007: analysis
core genome of Bacteria supports the present
scenario for the origin of life. A summary of this view
has been presented at the Institute for Systems Biology:
Presentation (1.3 Mb)
Note added 7th july 2007: In depth
analysis of genomes from Bacteria spanning the whole tree
of life is consistent with the scenario described here.
The genome splits into a paleome,
that recapitulates the scenario of origin, and a cenome,
that allows the cell to occupy a specific niche.
Note added 16th june 2009: The paleome
has to be split into two parts. The part meant to
replicate the genome and the part meant to reproduce the
cell machinery and casings. The latter, in turn, is split
into several groups of genes. Some manage chemical
frustration) while the rest manages energy-dependent
degradation of RNAs and proteins. The corresponding genes
behave as coding for Maxwell's demons, chosing to protect
what is young or functional.
other, more general, traces of homeotopy in present day
metabolism? If one follows the hypotheses of Granick ,
modified by Ycas , then more precisely stated by
Jensen , that enzyme specificity evolved by recruiting
proteins that already existed and catalyzed similar
reactions, ancestral metabolic traits should be found in
proteins that are grouped as similar in structure (and
most probably in amino-acid sequence). It follows that in
such families one could find traces of ancestral
As time elapses the number of such cases steadily
increases, and their number is growing rapidly as genome
programmes progress. Kaplan and Nichols, in 1983,
discovered that synthesis of para-aminobenzoate and
tryptophane was catalyzed by enzymes coded by genes trpD
and pabA derived from a common ancestor .
Goncharoff and Nichols further developed this observation
by showing that syntheses involving chorismate were
performed by enzymes exhibiting a significant degree of
similarity, such as enzymes synthesized from genes papB
(para-aminobenzoate synthase) and trpE
(anthranilate synthase) . Further work by these
authors and others showed that glutamine amidotransferase
was involved in synthesis of para-aminobenzoate,
tryptophane, as well as guanine (genes pabA, trpG
and guaA) and derived from a common ancestor [40,
41]. A further substantiation of the existence of a
primitive amidotransferase catalytic domain comes from
analysis of human CTP synthetase, where the glutamine
amide transfer domain is clearly related to the bacterial
Subsequently Parsot, Cohen and their colleagues
discovered that many activities involving pyridoxal
phosphate were strongly related, in particular in
synthesis or degradation of threonine, serine and
tryptophane (thrC, dsdA, ilvA and trpB),
as well as in enzymes involved in biosynthesis of
methionine (metB, metC in E. coli,
and their counterparts, in yeast) [45, 46]. In the same
way Schoenlein et al. identified a significant level of
similarity between enzymes responsible for the synthesis
of pyridoxal phosphate (pdxB) and serine (serA)
. This is most revealing in view of Wächtershäuser's
hypothesis of early surface metabolism, where
triose-phosphates had to play a major role (and this
contradicts Benner's dismissal of pyridoxamine as involved
in early living processes ). Along the same line, we
demonstrated that cysteine biosynthesis, in E. coli,
shares a common ancestor with tryptophane biosynthesis
. This, together with the observation that cysteine
and tryptophane codons are found in the same box of the
genetic code table (in company with the UGA selenocysteine
codon, also derived after homeotopic transformation from
activated serine), substantiates the hypothesis that
serine(-phosphate) was a general precursor of several
amino-acids synthesis and that tRNA was involved in the
process. Another old observation, the significant binding
of charged tRNAleu or tRNAval to E.
coli threonine deaminase, is well in line with this
hypothesis . Finally, we recently discovered that
there is a significant kinship between synthesis of
carbamyl-phosphate, and uridine-diphosphate in bacteria
. This is revealing when one remembers that aspartate
and carbamyl phosphate are precursors of pyrimidines.
But all this does not tell us directly what could have
been the precursors of these " holder " nucleic acids that
seem to have played an early role in evolution of
metabolism. It is clear that nucleotides are today part of
several coenzymes, as pointed out by many [10, 52, 53].
But it cannot be surmised whether this reflects a trace of
older structures rather than more recent adaptation of
long nucleic acid precursors to shorter structures.
Peptides are far much easier to synthesise than nucleic
acids. On the other hand, many coenzymes (e.g.
glutathione, pantothenate, folic acid ...) are (iso)
peptides, or contain peptides, often at their active
center. It is therefore interesting to explore whether
(iso) peptides have not been precursors not only of most
coenzymes, but of nucleotides as well. Many features of
extant metabolism are pointing in this direction, for
amino-acids are certainly present in the biosynthesis of
purines and pteridines (glutamine, glycine, aspartate and
serine, through formyltetrahydrofolate), or pyrimidines
But, as an indispensable self-catalytic step requires,
are (iso) peptides involved in synthesis of peptides? The
example of peptide antibiotics synthesis is a remarkable
illustration of such self-referring catalysis.
Biosynthesis of tyrocidin or gramicidin derives from
formation of peptide bonds, in the absence of ribosomes.
In tyrocidin, for instance, ten individual amino-acid
residues are activated by ATP (as they are in translation)
but are then transferred to an active SH residue of a
protein subunit, forming a thioester bond. Tyrocidin
synthesis begins after all ten sites of the enzyme complex
have been esterified with their specific residue. The
first three amino-acid residues react together
sequentially, forming a thioesterified tripeptide. From
this step onwards a phosphopantetheine cofactor transports
the growing peptide chain on each new residue in turn,
using its SH end as a carrier, and forms a new peptide
bond following a transthiolation step, until the end of
the process is reached when a decapeptide is formed (and
finally cyclised). This process is highly reminiscent of
synthesis of fatty acids from acetyl coenzyme A (which
contains a phosphopantetheine arm as a reactive center).
In this latter process acetyl-CoA is first transformed by
carboxylation into malonyl-CoA using ATP as an energy
source. A phosphopantetheine arm, bound to a core enzyme
makes a succession of transthiolation reactions that lead
to decarboxylation of malonate (this is the driving energy
source) and condensation of two methylene residues on the
growing chain. After six such steps the synthesis is
completed, yielding palmitic acid. Thermal agitation
supplies the only energy required for positioning of the
Analogy between both processes would only be anecdotal,
had it not been discovered that indeed, proteins involved
in tyrocidin, gramicidin and fatty acids synthesis share a
common ancestor , indicating that their origin is
common, and could be very old. This observation has been
substantiated by the study of many other sequences, in
particular from the programmes aiming at sequencing whole
genomes . Several features of these processes must be
emphasized: (i) a peptide is able to carry out synthesis
of a peptide; (ii) the same process permits synthesis of
both lipids and peptides; (iii) the process requires the
presence of active SH groups, essential components of
surface metabolism as proposed by Granick and
Wächtershäuser, and shown by De Duve to be of major
importance for the origin of life ; (iv) energy is
essentially derived from the formation of thioesters (and
carboxylation / decarboxylation in the case of fatty
acids); (v) among the amino-acids that are used, are
present both L- and D-amino acids (as well as a basic
amino-acid residue, ornithine, which cannot be
incorporated into proteins during translation, because it
cannot form stable adducts with tRNA).
If then, we accept that peptide formation is a very
ancient process (it could predate the invasion of Earth by
L-amino-acids), synthesis of peptide bond predating
translation, it becomes particularly important to assess
the hypothesis that nucleotides could have been derived
from surface metabolites containing peptides. In this
framework translation is a later invention, when tRNA
molecules, instead of simply offering a general holding
device for homeotopic transformation, have been involved
in an RNA-mediated process for peptide-bond formation. A
large number of examples where peptides can react by
intramolecular reaction to form new molecules can be
found. This is typical, for example of the antibiotic
nisin or other lantibiotics, where serine and cysteine
react to form lanthionin, a structural analogue of
diaminopimelic acid [56-59]. Another example of this
situation is the case of decarboxylases that use a
pyruvoyl active site, derived from self-processing of a
serine-serine dipeptide in the polypeptide proenzyme .
Organic molecules are usually presented as derivatives
of carbon chemistry. Yet it is clear that the organic
molecules present in living organisms display also a
very high content of nitrogen. This was not thought to
pose a difficult problem 40 years ago, when the models
of the primitive atmosphere considered it to be strongly
reducing, and rich in NH3. This is no longer
the case. And one now considers that 3.8 billions years
ago the atmosphere was mostly rich in CO2 and
N2. It is therefore of the utmost importance
for any model of the origin of life to propose scenarii
permitting to understand prebiotic nitrogen metabolism.
Following Granick's approach, it may be interesting to
analyze the present day situation of nitrogen
scavenging. In general, the process requires the
presence of iron-sulphur proteins such as ferredoxins as
electron transfer intermediates and molybdenum.
Ferredoxins are proteins constructed with a limited
number of amino-acid species, and they contain an iron
sulphur cluster, typical of what could be expected for
very early proteins. Molybdenum is a rare metal in
today's earth crust, but it is not clear whether at some
stage of earth evolution, or locally it could not have
been abundant. In addition this metal ion could be
replaced by other ions for the electron transfer process
at early stages of nitrogen fixation . The cofactor
molybdopterin is found in further complex oxidation
reactions. Now, molybdopterin is a sulphur containing
coenzyme - that could be therefore be interacting with
metal-sulphur clusters, that is made of a pterin moiety
derived from GTP, by cyclisation following loss of a
one-carbon formyl group. This step is catalyzed by GTP
cyclohydrolase, which yields pteridine triphosphate from
guanosine triphosphate with elimination of a one carbon
residue (precisely a residue transported by pteridine
containing coenzymes). Is it possible to consider that
the reverse reaction be a model for the straightforward
synthesis of nucleotides?
PteridineTP + HCOOH -----> GTP + H2O
We could then speculate that an autocatalytic process
permitting synthesis of pteridine (tri) phosphate could
have produced, as a side-product, the synthesis of GTP.
In this frame of thought GTP would have but been a
side-product of on-going nitrogen fixation.
This wild speculation would ask for a process
permitting synthesis of pteridine from peptides.
Exploration of extant microbial metabolism might give
clues for the plausibility of such processes. The fact
that many molybdopterin coenzymes contain nucleotides in
their structure is already consistent with this
Conclusion: a future for the origin of life
Several scientists convincingly proposed that life
emerged from a surface metabolism, rather than from a
poisonous broth. Granick's approach extensively used the
knowledge of extant intermediary metabolism. If his main
contention is right, this means that we are much nearer to
the origin than we could think of previously. Analysis of
biosynthetic pathways might therefore provide clues about
the original metabolic pathways and processes. The
hypothesis stating that early metabolism evolved through
specification of broad range catalytic activities can be
appreciated using comparison of enzyme structures in
living cells. Among the most prominent processes are those
which use tRNA molecules as carrier for homeotopic
transformation of more or less universal precursors. Among
such reactions, peptide bond formation could have evolved
well before translation. Peptides are therefore placed in
the limelight. They could have evolved before complex
coenzymes, allowing their own synthesis. Synthesis of
nucleotides would have been derived from nitrogen fixation
(for purines and ribose) and from condensation of
aspartate to carbamyl-phosphate (for pyrimidine
synthesis). In turn nucleotides would have produced RNA
carrier molecules, thus solving the chicken and egg
paradox raised by the generally accepted hypothesis of an
ancestral RNA world.
An interesting consequence of the depth of the
conceptual reflection of scientists is that concepts can
not only be organized to explain reality, but also to act
in a creative way, constructing a new aspect of reality.
This has been put into action for example when physicists
have created Laser beams. Thus, nothing precludes that
research in the Origin of Life results in new prospects:
this is already illustrated by the success of selective
Pasteur (1862) "Sur les corpuscules organisés qui existent
dans l'atmosphère. Examen de la doctrine des générations
spontanées" in : Leçons de chimie et de physique
professées en 1861 (à la Société chimique de Paris),
Paris, Hachette et Cie, p. 219-254 (back
1. Bernal JD (1951) The physical basis of life.
Routledge and Kegan Paul. London.
2. Granick S (1957) Speculations on the origin and
evolution of photosynthesis. Annals New York Acad. Sci.
In view of the fact that most investigators tend to think
that traces of the metabolic origin of life have been
erased (in particular via genetic takeover), it seems
important to cite in extenso Granick's view, which points
out the fact that present metabolism is an archive of the
past, rather than a palimpsest, as this may be used as a
convenient heuristic approach to scenarios of the origin
of life, as demonstrated convincingly by Wächtershäuser in
his model of surface metabolism:
"I shall propose [...] that this
unit originated from some common minerals; that the
minerals that contain metal ions served both as
coordinating templates and catalysts for various
reactions, and that around this unit were formed
organic molecules that gradually became organized into
units of ever-increasing complexity. Gradually,
biosynthetic chains developed in a stepwise fashion,
using small molecules to make molecules of
ever-increasing complexity. The metal catalysts became
modified into the metalloenzymes; in these new
complexes the same metals would now act as more
The experimental method whereby it is proposed to find
the evolutionary precursors of protoplasm is to
examine present-day biochemical reactions in
protoplasm and seek to relate them to reactions that
may have occurred and may still occur in the minerals
around us." ( back to
3. Cairns-Smith AG (1982) Genetic takeover and the
mineral origin of life. Cambridge University Press,
4. Wächtershäuser G (1988) Before enzymes and templates:
theory of surface metabolism. Mic. Rev. 52, 452-480
5. Schrödinger E (1944) What is life ? (reed. 1967)
Cambridge University Press, Cambridge.
6. Danchin A (1990) Une
aurore de pierres. Aux origines de la vie, Le Seuil,
7. Dyson FJ (1985) Origins of life. Cambridge University
8. Cech TR, Bass BL (1986) Biological catalysis by RNA
Annu. Rev. Biochem. 55, 599-637.
9. Danchin A (1983) L'Œuf et la Poule. Fayard, Paris.
10. Benner SA, Allemann RK, Ellington AD, Ge L, Glasfeld
A, Leanz GF, Krauch T, MacPherson LJ, Moroney S,
Piccirilli JA, Weinhold E (1987) Natural selection,
protein engineering, and the last riboorganism : rational
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11. Wächtershäuser G (1990) Evolution of the first
metabolic cycles. Proc. Natl. Acad. Sci. USA 87, 200-204.
12. Danchin A (1986) Préface in Qu'est ce que la vie ?
(translation of E. Schrödinger What is life?) C. Bourgois,
13. Wong JTF (1975) A co-evolution theory of the genetic
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