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Pioneer 3(1): 7-17, 2008 |
HYPOTHESIS |
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© Truthfinding
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ORIGIN AND EVOLUTION OF
LIFE |
A Fundamentally New Perspective
on the Origin and Evolution of Life
Shi V. Liu
Eagle
Institute of Molecular Medicine
SVL@logibio.com
(Received 2008-11-13; revised 2008-11-21; accepted
2008-12-10; published 2008-12-11*)
Motto
Criticism and attempted “falsification”
are essential parts of science.
- Philip J. Darlington, Jr. (1904-1983)
HIGHLIGHT
A fundamentally different perspective
on the origin and evolution of life was provided over 17 years ago and should
be seriously considered today by all researchers in the field of evolution
study.
ABSTRACT
KEY WORDS
Life, Origin, Evolution,
Common ancestor, Different ancestors,
Next year will be the 150th
anniversary of the publication of Darwin’s famous book “On the Origin
of Species by Means of natural Selection or the Preservation of Favored Races
in the Struggle for Life” (1) and a celebration for the 200th birthday of a most
influential biological scientist of all time (2, 3). There is no doubt that Darwin’s
view has contributed greatly to the winning of
a strong voice for science in explaining the most interesting but also the most
perplexing question that humanity has confronted with
– when, where, and how life originated and evolved. However, is Darwinian view really a truthful
reflection of the natural history of life?
Are there any other perspectives that worth of consideration and may
ultimately be proven more compelling than Darwinism in explaining the origin
and evolution of life?
Presented here is an abstractive summarization of
various mistakes contained in Darwinism which include not just
Fundamental flaws of Darwinism
Due to the dominance of
Darwinism in evolution study, it is difficult to directly express a different perspective
without proving a minimal necessity of offering that perspective. That minimal necessity may come with a
realization that Darwinism, no matter how popular it is, is still far from a
complete understanding of life history.
Over the past time there have been many criticisms
on Darwinism (5-7). It is beyond the scope of this
communication to summarize all of these criticisms. However, the following list may show some
major shortcoming and inconsistency in the Darwinian view of the life history.
1. Gradual
evolution was not backed by fossil records.
The
history of most fossil species includes two features particularly inconsistent
with gradualism as conceived by Darwinian evolutionists (8-13): a stasis during which time most species exhibit no directional change and a sudden appearance of different species in many local areas as “fully formed”. Evolutionary
process also
appears to have different phases, some
periods having considerable evolutionary activity and some periods being
comparatively quiescent.
2. Evolutionary
progress is not a random process.
Evolution
has been a one direction irreversible process as shown by the fossil records which is inconsistent with prediction made by randomness (5, 14, 15). Order prevails in the formation of protocell as it is shown that amino acids turned to be “self-sequencing” and DNA
and RNA are built of a phosphate and sugar backbone (16). Thus when cells
come into existence, they come in a way different from that foreseen by randomness.
As stated
by Darlington, all processes of directional change (which include evolution of
life) are programmed to some extent by the composition and limits of the sets
concerned, and by environmental factors, even though complex evolutionary
processes are at the same time partly open-ended (17).
3. Gene mutation
is not the main overall mechanism of evolution.
Evolution of biochemistry preceded the innovation of
genetic system. Form and function arise
from the physico-chemical and mineral imprints of the previous levels of evolution.
Genes and chromosomes influence form and function of life but this is not tantamount to them being the
originators of these processes. Their
intervention is at a secondary level, deciding only what variant of form and
function will become fixed. Mutation alone
cannot explain
the increased complexity as reflected in the increase of genome size. Thus, it is impossible to understand evolution of coordinated
complexities purely in terms of piecemeal accumulation of random mutations. As a matter of fact, attempts in dating evolutionary process using the
molecular clock driven by gene mutation have generated more inconsistence than
consistence (11, 18, 19). Alarm was even raised: molecular clocks run out of time (20).
4. Natural
selection is a vague term and should
be better replaced with a concrete physico-chemical
mechanism.
Natural selection is currently
defined as the
process by which favorable heritable traits become more common in successive
generations of a population of reproducing organisms, and unfavorable heritable
traits become less common, due to differential reproduction of genotypes. In the original words by Darwin, natural
selection is defined as “preservation of favorable variations and the rejection
of injurious variations” (1).
This definition describes an
outcome of a process rather than a mechanism for a process. As a matter of fact, the original
concept of
natural selection was developed in the absence of a valid theory of inheritance
because nothing
was known about genetics at the Darwinian time. As
pointed out by Darlington, “almost all writers on evolution use natural
selection, but hardly anyone tells us what it is or how it works”(21).
To be meaningful for evolutionary study, it is
essential to replace a vague term “natural
selection” with a concrete physico-chemical process so its actual interaction
with a living organism can be measured in well-defined units (22, 23).
5. The notion of
“common origin” from a last common ancestor cell may be the most erroneous
guess.
Theoretically it is unbelievable that only one
ancestor cell formed in a life-forming environment that
seemed to prevail in an enormous space. It might also be
extremely difficult for a single cell to proliferate fast enough to account for
the rapid appearance of different life forms and the wide distribution of
living organisms on Earth. It has
not been shown why the common ancestor cell should diversify into many other
forms if they lived in the same environment or why a same global change of environment could have a differential selection so that many different
progenies produced and stabilized.
It should be emphasized that “similarity” in life forms can
also be resulted
from truly independent events taking place according to a common mechanism. The current phylogenetic studies have not rigorously
rule out this possibility in their tree constructions. And there is
no reason to deny that there may be more than one precursors in pre-cellular
phases such as the surface metabolism, the RNA world, the RNP world and the DNA
world that would independently “cellularized” (24).
6. Current
mainstream evolutionary theories separated the evolution of Earth from the
evolution of life.
This separation occurs because biological evolution is
based on the mutation of genes which does not belong to inorganic non-living
world. This has created a mysterious
cloud around the biological subjects and delayed the approaches of deciphering
the biological world by the same laws that governed the abiotic world. However, as
we look into the
deeper level of biology, we actually see more and more connections between the biotic world and
the abiotic world (25-28). In the words of Darlington, prebiotic and
biotic evolution on the earth’s surface is a continuous, energy-requiring
process (17).
A fundamentally different perspective on evolution
As a result of the above
literature review a new perspective on the origin and evolution of life was proposed in 1991. The original paper was entitled “Evolution:
an integrated theory - Criticisms on Darwinism” which
was a thesis for my graduate course on
microbial evolution. It was published only much
later in 2006 for an obvious reason (4).
Summarized here are the key
points of that “new” but actually 18 years-old perspective on evolution, with
some updated information:
1. Evolution consists of two organically connected sides: the
abiotic evolution and the biotic evolution.
Evolution is a phenomenon inherent to the construction
of the universe. It actually starts with the formation of elementary particles at the
dawn of the conversion of energy into matter (29). Evolution
starts when the universe is born.
Evolution cannot be considered solely as a
biological process. The elementary
particles, the chemical elements and the minerals have each had an autonomous
evolution (25, 29). Biotic
evolution was anteceded by these three levels of evolution. Evolution
of life on Earth is one component of the overall development of the Earth. The biotic and abiotic worlds are organically
connected and have mutual influence on each other’s development (17, 26, 30-33).
2. Evolution is
governed by some fundamental laws.
Evolution
of both abiotic and biotic worlds is governed by some common fundamental laws (34). Evolution is an entropic phenomenon, a natural consequence of the
behavior of physical information arrays in an entropic universe (35). Evolution in general or totality is characterized by
increasing entropy as evidenced by increasing complexity and diversity. Thus, evolution is result of the interplay between energy
and entropy and follow some basic laws such as the second law of thermodynamics
(35, 36).
Speaking of biotic evolution, some people have
argued that entropy rules out evolution because the order produced within cells is
more than that compensated for by the disorder they create (37). Indeed,
energy or order is usually associated with normal life and those molecular
guardians that ensure it, but entropy or disorder has been associated
with disease (38). Such
postulated prevention of or yet resistance to entropy in order to maintain
normal life and thus ultimately direct evolution has meanwhile been recognized
by several investigators (23).
However, it must be pointed out that whether or not
a thermodynamic law can be directly applied is also dependent on the nature of
the system and its reference to the surrounding environment. In some circumstances, it even depends on how
the law is defined or interpreted. For
example, the second law of thermodynamics states the total entropy of any
isolated thermodynamic system tends to increase over time. The universe is an isolated system. Thus its total entropy would naturally
increase. However, individual life is
not an isolated system but is openly connected with its environment. Thus, any consideration of entropy balance
and the correctness/applicability of physical laws must take into account of
the nature of the system (39).
When the totality of life forms in an isolated
universe is considered, we must realize that it is the dispersal of energy
(another way to define entropy) from
initially fewer forms of life to later on more forms of life that captured a
global picture of evolution over the geological time. This change in the biotic world is consistent
with an increase of entropy if we agree that the emergence of new forms of life is either due to a
mutation (a kind of disorder) of one life form or a mixing of different life
forms (a kind of entropy mixing which leads to an increase of entropy in the
system even if there is not net exchange of heat or work).
Thus, I still firmly believe that “any theory claiming to describe how organisms originate and continue to
exist by natural causes must be compatible with the first and second laws of
thermodynamics.” (40).
3. Evolutionary
process is a network of consecutive loops of current flow reactions.
Currents of energy flow and mass flow are common to
both abiotic and biotic systems. The
global current flow can be resolved into a series of current loops originating
at source points and terminating at sink points (41). Each source
serves to drive cycles of matter around the reaction loops. The beginning of the Earth system is the
network in small molecule space. The
transition from small molecule space to macromolecular space and then to
organism space represents a reflexive autocatalysis network of loops. The global
pre-biotic ecological cycles, with Sun being the radiation source and outer
space being the infinite isothermal reservoir, provides the functional basis
for biogenesis.
4. Evolution is
an ordered process and the pattern realized in the foregoing loops channeled the development of subject in the following loops.
As the system has aged it has explored Platonic space
in a highly directed way (highly nonrandom). The reactions in the foregoing loop canalize the
potential of the reactions in the following loops. The central problem of evolution is not the
“origin of species” but the origin of form and function. The biotic evolution was preceded by the
abiotic evolution (42) and thus it cannot depart from the frame created by
the physico-chemical laws and rules. Formation of different life forms is a type of events
determined by the physico-chemical identity of corresponding pro-cellular
matters (43). The process of evolution is not a random
process (14, 29, 43, 44).
Matter takes the forms of life because it has the
inherent capacity to do so. The kinds
and numbers of genes available to form sets (genotypes) are limited and
selection even further eliminate “unfit” combinations (17). Thus, even
though the overall evolution process can be considered as a kind of losing
order and thus increase of entropy, each individual evolution process still
follow some specific mechanisms intrinsically determined by the matters
comprising that line of evolution.
5. Life forms
had originated at multiple places and may have arisen multiple times.
Life forms, even the same form of life, can be formed
at multiple locations on Earth as long as the environmental conditions that favored their formation are the same.
Different life forms may arise in different geological times (45).
Arguments have been made on
what the earliest life form was (46-50).
However, any argument on this matter must be discussed in the context of
contemporary environmental conditions and how the emergence
of the biotic forms alters the abiotic world.
Furthermore,
when discussing how living beings emerged from abiotic components (in similar
ways at different locations), it is worth mentioning a more recent hypothesis
on a peptide origin of life (51). It postulates that secondary
to the formation of oligopeptides from amino acids under conducive prebiotic
conditions such as those involving (volcanic) carbonyl sulfide as a catalyst (52), further peptide bond
formations engender the production of significant amounts of water which along
with carbon dioxide could be processed in photosynthetic reactions to generate
oxygen and those higher organic matter building blocks that are necessary for
the emergence of life (51).
6. Biotic
evolution showed distinctive phases which had its own mechanism and was
influenced by the corresponding abiotic evolution.
The
history of the biological evolution may have different phases determined by the
abiotic evolution of Earth environment.
Each phase may produce specific change(s) of certain components of
living system (in other words the variation may be shown in different ways) (53). Thus the
reconstruction of its history may not be achieved by using a single universal yardstick (12).
7. The evolution
of different branches of life forms may have different rates and this unbalanced
evolution allows the co-existence of so many types of life forms in a
contemporary time and common space.
The
evolution potential and the speed of evolution are determined by the
distinguished physico-chemical properties of each life form. This independence
gave an unbalanced evolution of different life forms. The
co-existence of diversified types of the extant and/or extinguished life forms
in the contemporary time and common space is a manifestation of such property (9).
The
multi-origin and multi-line scenario of life evolution actually adds more
dimensions to the thermodynamic operation of evolution. From the very beginning, the increase of
entropy of the living world might not just be a result of mutation (disorder)
but more likely a result of combination of mutation and mixing (horizontal gene
transfer and symbiosis for example).
Thus the
ruling out of entropy
from the evolutionary process simply because life feeds on negative entropy or
“negentropy” (54) may be a misunderstanding of the history of life.
Obviously, this new perspective
on evolution does
not fit into any aspect of the Darwinism
because it basically contradicts all the fundamental
assumptions withheld by the Darwinian Theory on evolution. However, if we agree with Darlington that “much
widely accepted evolutionary and sociobiological theory, presented by the most
influential evolutionists, is wrong and therefore dangerous” (21), then everything on evolution should be open to full discussion.
Increasing new evidence contradicting Darwinism
Now seventeen years have
passed since my initial proposal of an alternative perspective on evolution,
was I too naïve in asking some “stupid” questions or did I actually trip over
some intelligence on evolution?
Let
me take a quick look at some most important developments in recent evolutionary
studies.
1.
The search for
the Last Common Ancestor (LCA) or Last Universal Cellular Ancestor (LUCA) has
not lead to any clear answer but more contradictions (46, 55-64). It has even
become increasingly hopeless to find any single “root”
as more and more evidence now show the deep branches of the Tree of Life (TOL)
actually look more like “rings” or “networks” (65-67). What does this mean? There was
no common ancestor cell for all the life forms formed later. The
cellular life was already a “forest” when we first saw it (4, 68).
2.
The application
of any single “molecular clock” for calculating the speed of evolution has
resulted in repeated timing errors not only against
geological time tables but also within biological time tables (69-72). This means that evolution may
not be a single line linear process operated under a single mechanism (of gene
mutation).
3.
Many claimed “missing links” are still missing despite many hard efforts in
searching them. Do we have any chance to find these “missing links”
or do they really exist or existed-once but then disappeared? Is it actually necessary to find these
“missing links” in order to “complete” our reflection of the history of
evolution? The answers depend on whether
you still believe that there was a LCA or not.
When there was no LCA, the “links” are unnecessary because each
different pre-cellular ancestor can evolve into different cellular life forms
without requiring those intermediate linkages.
In other words, there are natural “gaps” between different lines of
evolution.
4.
Many assumed
single line linear evolutions contrast with
more and more solid evidence of multi-line
coevolution (73-75). Coevolution/co-evolution (76-79) or “collective evolution” (80) has become a prominent theme in evolutionary studies (73, 81-93). But this coevolution may be a natural outcome of the parallel evolution of
independently originated multi-lines of life forms. Thus the “pattern pluralism” on the Tree of
Life (74, 94) may be a collective perception of related but
independently evolved entities rather than diversified entities came from a
single origin.
Besides
these generalized overviews of the recent progresses in evolutionary studies, I
am more encouraged with seeing some solid conclusions contained in some recent
publications by the following individuals.
For example, Carl Woese has come to a realization that “The universal ancestor is not a discrete entity. It is, rather, a
diverse community of cells that survives and evolves as a biological unit” (95). Doolittle
also pointed out that “a single tree-like pattern is not the necessary …… Pattern pluralism is
an attractive alternative to the quixotic pursuit of a single true TOL.”(94). Koonin et al. have
concluded that “The last universal common ancestor (LUCA)
……was not free-living but an inorganically housed assemblage of expressed and
replicable genetic elements” (96) and discussed the ancient virus world in relation with the evolution of
cells (49). Eugene Koonin later also showed
that the patterns of life emergence on earth can be better explained by a Biological Big Bang model (97). Patrick Forterre
proposed that
the transition from RNA to DNA genomes would have stabilized the three canonical
versions of proteins involved in translation, whereas the existence of three
different founder DNA viruses explains why each domain has its specific DNA
replication apparatus (47). Michael Lynch stated that the
origins of many aspects of biological diversity, from gene-structural
embellishments to novelties at the phenotypic level, have roots in nonadaptive
processes (98)
So, evidence conforming to
my different perspective on evolution is increasingly incoming. More importantly, many remaining “puzzling observations” and “intriguing conflicts” can be easily resolved with a
multi-origin parallel evolution view. For example, the existence for certain pairs of amino acids with
an unclear biosynthetic relationship between the precursor and product amino
acids and the collocation of Ala between the amino acids Val and Leu belonging
to the pyruvate biosynthetic family (73) may not be viewed as a confrontation with the coevolution the occurrence of highly similar genetic modules in
diverse organisms needs not to be explained by the assumed highly leaky
membranes and the assumed high level of horizontal gene transfer (HGT) (99, 100). This is
because some same genetic modules can be sealed into different cells at the
major transitions from acellular to cellular life (4, 68).
Thus, considering so many
problems with the traditional views on evolution, the old-fashioned view such as the
“Darwinism” should be replaced by insightful knowledge (101). I may be wrong in proposing a fundamentally different
view than Darwinism. But If I am right, all interested persons should not
stubbornly refuse to face my view.
Conclusions
The central position of this new perspective on evolution is that cellular life forms might have multiple independent origins that were
rooted in different acellular forms. The
formation and evolution of life is not random but abides some physico-chemical
principles. Each independently
originated cellular life form may evolve under separate phylogenetic lineages
and may also interact with each other to form more complex higher order life
forms. Thus, the images of the life
history as reflected by the later reconstruction efforts may appear as
“mosaics” and show some pattern pluralisms.
The “Tree of Life” (TOL) may serve better as a classification scheme for
grouping life forms with similar structure and function rather than as a
tracing tool for identifying the phylogenetic relationship and even the
so-called the Last Common Ancestor (LCA).
I wish this different perspective
on the life history will enhance our
understanding about the origin and evolution of life. I sincerely invite all people interested in
evolutionary study to voice their opinions because I
truly believe debating controversies can enhance creativity (102). Remember, “in the history of science,
it is the change in perspective that has usually been the most important” (103).
To celebrate
Darwin as a great scientist (3), we should fulfill the dream of a scientist to
advance science with continued efforts.
This is because, what characterizes science is its search for a logical interpretation of a given
event. The agreement between the
interpretation and the phenomenon depends on the amount of knowledge available
at a given time. Science is not afraid,
in the long run, to change completely its outlook and position. Good science provides for a continuing search
for new ground and review of old (4).
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Appendixes
1.
History of this manuscript.
This
manuscript was evolved from a Comment submitted to Biology Direct. Dr. Eugene
Koonin has provided many valuable inputs in the transformation of that Comment
into a Hypothesis type manuscript.
However, this does not necessarily mean that he is in agreement with the
views expressed in this manuscript.
Request for reviewing this manuscript has been sent to over 13 board
members of Biology Direct including
Drs. Eric Bapteste, Juergen Brosius, Ford
Doolittle, Patrick Forterre, Peter Gogarten, Simonetta Gribaldo, Gaspar Jekely,
Alexey Kondrashov, Doron Lancet, John Logsdon, Bill Martin, Arcady Mushegian
and Anthony Poole. However, only one
board member sent back a review. Some
stated of lack of time to do the review and most other simply ignored the
request.
The
manuscript was also sent to Dr. Carl Woese wishing that he can communicate it
to PNAS or write a review. He declined both requests and suggested a
direct submission to PNAS. The direct submission was rejected by PNAS because “The Board concluded that
while interesting, your paper lacked the broad appeal necessary for further
consideration”.
2.
Review received and agreed to be published.
A review from Dr. Juergen
Brosius of
This
is a convoluted manuscript that uses a broad spectrum of arguments to highlight
fundamental flaws of Darwinism.
First
of all, I endorse colleagues like Dr. S.V. Liu who support open review,
generally speak their mind and challenge existing dogmas, procedures and
establishments, albeit perhaps in a somewhat overzealous way. For my part, I
think it is a disgrace for the scientific community to have allowed silencing
of fraud investigators such as NIH Walter Stewart and Ned Feder – instead of
channeling their presumed eagerness. The inflation of non-reproducible results
in the literature mostly due to carelessness urges the establishment of an NIH
Institution to curtail negligence and fraud. I agree that with better scrutiny,
one or the other Nobel Prizes would not have been awarded. Not so much because
of fraud, but I am aware of a case, where the Nobel prize winner’s major
publications rarely stood the test of time.
Back
to the manuscript, I did not detect much that could rock Neo-Darwinism. Admittedly,
Darwinism can be interpreted sensu lato
or stricto, and this might be the
underlying cause for much of the disagreements in the area of evolutionary
biology. Criticism of Darwinism seems to be a sure strategy to get
attention, and unfortunately, the most from creationists and other
non-scientific groups. Many arguments are (perhaps meanwhile) not new. Life
being at odds with the second law of thermodynamics is one of them. Entropy
only strictly increases in an isolated system, but there are no completely
isolated systems in nature (except maybe the universe as a whole) http://www.talkorigins.org/faqs/thermo/entropy.html
In order to establish
priority for some of the author’s ideas from more than a quarter century back,
it would be important to have access to the original version of the graduate
thesis from 1991 (although it might not matter anyway, as the ideas did not or
will not stand the test of time).
Unlike the author - I
do not see such a strict line between non-living and living materials. The key
is, what the environment permits. Conditions in our sun almost exclusively
permit the presence of hydrogen and helium (much in ionic form), as well as low
amounts of the other elements. Molecules are permitted to form under conditions
of planets. The conditions on planet Earth were also conducive to forming more
complex molecules and macromolecules. The fact that our planet chanced upon a
macromolecule that was self-replicating – something that could be considered
the beginning of life - might be of extreme rarity but probably not unique in
the universe. From this first replicator - whether it was RNA initially or at a
later stage (transitions are plausible [1,2]) - it is easy to see how RNA
molecules replicate themselves and other RNA molecules and, entrapped in
inorganic compartments or lipids, you are looking at some of the first cells.
From there, by duplication of RNA molecules (simultaneously being hereditary
and catalytic entities) with concomitant alteration, it is not difficult to
envision the transitions to an RNP world [3] and from there to DNA containing
cells by retroposition – enzymatic conversion of RNA to DNA [4]. There is no
need for the proposed rise of several independent nucleic acid based cellular
precursors, a scenario much less parsimonial. Importantly, the RNA world
already was firmly rooted in the main foundations of Neo-Darwinian
evolution, namely amplification of hereditary material with modifications and
natural selection [5]. Other layers of evolutionary principles come and go or
vary in significance over time [see Fig. 5 in ref. 5]. Even the fact that the human lineage is at the
verge of yet another transition, namely into something akin to Lamarckism does
not falsify the underlying Neo-Darwinian
evolution [6]. Likewise, I do not see any problems with communal cellular
evolution prior to the Darwinian Threshold [7]. Already, in the RNA world,
exchange of RNA molecules = genetic material would have been quite rampant [5].
Importantly, RNA aptamers evolve even in the test tube following Neo-Darwinian principles [6].
The lack of missing
links [see ref. 8] is not at odds with Neo-Darwinism.
Erratic molecular
clocks (in mammals possibly explained by different generation times) are not at
odds with Neo-Darwinism.
Having more than one
common ancestor is not at odds with Neo-Darwinism.
Independently evolved
forms of life are not at odds with Neo-Darwinism.
Imagine a life form that arose on a different planet, it would evolve under
different conditions but almost certainly in a Darwinian way.
Even if there were
flaws, they are by no means “fundamental”. Despite the fact that evolution at
the genome level is neutral to a large degree [9], it is amazing how well
Darwinian principles apply, despite the fact that
Other points:
I do not understand
the meaning of the following sentence: “Thus the reconstruction of its history
may not be achieved by a single universal ruler…”
I do not understand
the following: “…that amino acids turned to be self-sequencing…”
Typos or grammar:
“However, considering
the still lack of its recognition…”
“…or did I actually
tripped over some intelligence on evolution?”
Should be Koonin et
al.: “Eugene et al. have concluded that “The last universal common ancestor
(LUCA) ……was not free- living but an inorganically housed assemblage of
expressed and replicable genetic elements…”
References
1) Cairns-Smith, A. G.
(1982) Genetic takeover and the mineral origins of life.
2) Maynard Smith, J.
& Szathmáry. E. (1995) The major transitions in evolution.
3) Brosius (2001)
tRNAs in the spotlight during protein biosynthesis. Trends in Biochemical
Sciences 26, 653–656.
4) Brosius (1999)
Transmutation of tRNA over time. Nature Genetics 22, 8–9.
5) Brosius J (2003)
Gene duplication and other evolutionary strategies: from the RNA world to the
future. J. Struct. Funct. Genomics 3, 1–17.
6) Brosius, J. (2005)
Disparity, adaptation, exaptation, bookkeeping and contingency at the genome
level. Paleobiology 31(2), 1-16.
7) Woese, C.R. (2002)
On the evolution of cells. Proc. Natl. Acad. Sci. USA, 99, 8742–8747.
8) Gould, S.J. (2002)
The Structure of Evolutionary Theory. The Belknap Press of
9) Lynch, M. (2007)
The origins of genome architecture. Sinauer Assoc.,
* The publication
here is the same as submitted to PNAS, except for the added highlight, abstract and
keywords.