Download How Life Began – Evolution`s Three Geneses

Article type: review article
Title: Noah and the spaceship: Evolution for 21st Century Christians
Ellen Clarke, University of Bristol
Philosophy Department, University of Bristol, 9 Woodland Road, Bristol, BS8 1TB,
UK
Fax: +44 (0)117 928-8626
Tel: +44 (0)7986 836528
Email: [email protected]
Review of “How Life Began – Evolution’s Three Geneses” by Alexandre Meinesz,
translated by Daniel Simberloff.
Abstract:
Evolution has increasingly become a topic of conflict between scientists and
Christians, but Alexandre Meinesz’s recent book How Life Began aims to provide a
reconciliation between the two. Here I review his somewhat unorthodox perspective
on major transitions, alien origins and the meaning of life, with a critical focus on his
account of the generation of multicellularity.
Key words:
Christianity; major transitions; panspermia
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Meinesz is already known as a popular science author for his work Killer Algae
(1999) about the dangerous spread of non-native algae. As a phycologist he is a little
further away from his home territory in this book which attempts the much grander
task of assimilating biology, history and philosophy into the sort of text that wouldn’t
look out of place on the bookshelf at Sunday school. This is evolution for the
religious, the book of Genesis rewritten for the modern world. It combines personal
reflections on art with summaries of the latest discoveries in molecular biology and
paleoecology to offer a uniquely spiritual perspective on cutting edge science.
Meinesz claims there have been three distinct geneses or creations in evolutionary
history. One is the origin of bacteria (about which he says surprisingly little, save that
it didn’t happen on earth). One is the origin by symbiosis of the eukaryotes - which is
actually a rather heterogeneous collection of separate transitions, including the origins
of the nucleus and of sex, supposedly unified by the common mechanism of
symbiosis. The third and last is the origin of multicellularity. It is not entirely clear
what these three ‘events’ have in common, that could distinguish them from many
other candidate transitions such as the origin of life, the origin of chromosomes, the
origin of cell walls, the origin of language, or the origin of superorganisms or
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colonies. He distinguishes four fundamental forces or motors of evolution – mutation,
sexual recombination, natural selection by the environment and mass extinctions or
cataclysms. He emphasizes contingency in evolution, as well as union – the alliances
and aggregations that have made the evolution of complex life possible. Like Gould
(and McShea) his emphasis is on a long term paleontological view of evolution which
emphasizes the success and longevity of bacteria, in contrast to a more progressive or
adaptationist view.
Some highlights are worth mentioning - chapter three is devoted to bacteria, in fact
it’s a tribute to them. We learn about their astonishing super-powers, their incredible
diversity and resilience, their unsurpassed dominance in terms of numbers and
longevity on the planet, as well as their indispensability to all other forms of life.
Chapter six looks at controversies in the history of biology regarding large scale
trends and the tempo of evolution with an impressively accessible treatment of the
epistemological problems that paleoecologists face. He explains how different sources
of evidence are collected and combined to try to reconstruct the history of life, and
how the limitations of these sources of evidence constrain and possibly bias that
picture. There is lots of science here – real photos of specimens and details about
dates, combined in a way that lets the reader feel what it must be like to be at the
forefront of science. Chapter nine contains the high point of the book – the issue of
the so-called sixth mass extinction. Here he manages the difficult task of stirring your
passion on an issue that is so well-rehearsed in these sorts of books that it is difficult
to write about without sounding like you’ve simply copied it all down from some
ecological holy book. Yet Meinesz manages to breathe new life into the topic.
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How Life Began would be called a work of popular science, although it is as much
history of science as science, with a good deal of philosophy thrown in as well, which
is a huge amount of ground to cover in just one book. He covers most of the major
debates in recent evolutionary biology and parts of the work are dense and rich, but
other times things are rushed over so fast that I wonder what the lay reader would
really have gleaned from it. The book opens with a motif that runs throughout the
work – a description of a painting of Antoni van Leeuwenhoek by Vermeer, which
Meinesz uses as an illustration of science as he claims it ought to be done – with one’s
attention turned to the infinite and the mysterious but with one’s feet placed firmly on
the ground. All chapters open with some sort of concrete setting, a personal anecdote
or a distant memory recalled, demonstrating the author’s determination that he doesn’t
sound like a distant inaccessible scholar lecturing from his ivory tower. Meinesz is
keen to reassure the reader that his great intellect does not preclude him from reaching
out to mere mortals.
Largely Meinesz’ efforts to inject his story with spiritual and artistic flourishes left me
cold. I found them clumsy and patronising at best. Maybe there are issues of
translation here, or maybe just turns of phrase that only a philosopher would object to
– for example, he claims that the origin of life entails the origin of the first cells
(Meinesz 2008, 23). At his worst he is arrogant and chauvinistic – why does he want
to alienate half his readership by interrupting his chapter on bacteria to muse on the
thought of a “beautiful woman with bare breasts” (Meinesz 2008, 65)? Some chapters
feel more like random collections of essays than coherent pieces of a larger story, and
some of it is downright repetitive although his writing is at its strongest in the most
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scientific parts, where you feel that he benefits from letting go of his stiflingly selfconscious desire to sound profound.
Three features of this book make it stand out from the crowd of other books on the
history of life, such as Dawkins’ Ancestor’s Tale or Maynard Smith & Szathmary’s
Major Transitions in Evolution (which Meinesz conspicuously fails to mention.)
Firstly, panspermia. Although this book is entitled ‘How life began’ it does not
actually treat the origins of life at all, it merely discusses the arrival of life on earth.
Secondly, the emphasis on union – symbioses and endosymbioses. Meinesz claims
that these kinds of relationships represent a revolution, a schism, under-represented in
evolutionary theory and a departure from Darwinian evolution. Thirdly, and most
conspicuously, religion. This is a self-consciously spiritual work of popular science
which some might find jarring. You cannot ignore the religious content in this book,
nor easily separate it from the scientific- in fact a discussion of the relationship
between evolution and Christianity comprises the heart of several chapters. I’ll
discuss all these departures, as well as carrying out a critical examination of his
treatment of one of the more conventional topics – the transition to multicellularity.
Panspermia (or more properly, exogenesis).
Meinesz devotes a whole chapter to defending the theory that life originated on an
alien planet before seeding earth and it is evidently one of his favourite axes to grind
(although I struggled to find further work on it by him). It is a passionate defence,
using various plausibility arguments as well as giving an impressively clear account
of some fairly convoluted evidence. Meinesz presents evidence from Friedmann
showing that the meteorite ALH84001 dated to around 4.5 bya (and originating on
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Mars) contains traces of compounds (magnetite chains) usually only formed by
bacteria. Supporting evidence suggests that there is a very low possibility that such
compounds were formed in abiotic reactions such as mineralization especially since
they were found aligned into perfect ‘necklaces’ just as in our cells. He further argues
against the possibility of contamination of the meteor or samples. Meinesz
acknowledges widespread controversy as to the veracity of these claims, but attributes
it to personal jealousy and conservatism. What mainstream science would have to
gain by sidelining such evidence is not spelt out. This bit reads as a fascinating insight
into the lives (and political battles) of scientists and it would add up into a reasonable
hypothesis if it wasn’t so obviously one-sided and if he showed at least an awareness
of the typical response of most evolutionists to panspermia theory. Meinesz offers no
answer to the ‘So what?’ problem. What difference does it make? Most evolutionists
find panspermia a hypothesis with limited appeal, simply because it seems to want to
side step the mysteries that really get evolutionists going, by removing them to a more
distant location. Panspermia per se does not solve the problem of how life originated,
it simply extends the available time frame and environment. Meinesz chooses not,
after all, to discuss hypotheses about how life began at all and, like Will Wright’s
computer game ‘Spore,’ simply starts at bacteria.
Unions
Meinesz intends his work to emphasize the power of an oft-neglected force in
evolution– symbiosis. French biology since Portier has tended to pay more attention
to unions in biology than have the anglo-american traditions (see Sapp 1994 for a
history), with their greater attention to individuals and to competition, and that
tradition is continued in this most patriotic of books. We are presented with the Elysia
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sea slug, hero of Meinesz’ previous book Killer Algae, to illustrate the manner in
which lineages can borrow traits from one another by symbiosis. The slug apparently
preys on Caulerpa, a tropical alga, and ingests the alga’s cytoplasm without digesting
its chloroplasts. It then deposits the chloroplasts under the surface of its skin where it
uses them to produce energy just like a plant ordinarily does. It is a slug that
photosynthesizes. Meinesz tells the tale well and inserts it within a larger piece on
symbioses and the role they have played in major transitions in evolution. He draws a
direct analogy between the sea slug using stolen chloroplasts, and prokaryotes using
engulfed mitochondria to become the first eukaryotes in Margulis’ endosymbiosis
theory.
It is great that Meinesz puts so much emphasis on this defining kind of union in
evolutionary history, and he is honest here in presenting competing hypotheses and
emphasizing the speculative nature of some of the claims. The somewhat dense
material is also aided tremendously by his cheerful little cartoon storyboards. Yet the
details don’t all come through crystal clear, and at times this chapter is muddled,
partly because there is just too much in it. For example, the role of symbioses more
generally in evolution is left unclear, so that it seems indistinguishable from coevolution, and the text gets muddied up by non-precise use of terms like ‘individual’
and ‘partner’ which is common but damaging to a discussion of endosymbiosis. I
also take issue with the extent to which Meinesz wants to claim that symbiosis is a
process different in kind from Darwinian evolution. He declares it a revolution and a
new genesis. But these are not equivalent. Evolutionary transitions in individuality
such as the origin of eukaryotes and of multicellulars do indeed comprise new geneses
in that they create objects at new higher levels of selection, but they are generally
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perceived as occurring due to standard Darwinian processes of variation and selection.
Symbiosis may count as a different source of variation than mutation, especially if we
insist that not all new behaviours have genetic mutations underpinning them, but so
does lateral gene transfer, polyploidy and sex. It is true that symbiosis has often not
been given a sufficiently important place in the history of life, but the optimal way to
redress this balance is not to cry revolution.
Many evolutionary histories restrict their examination of aggregations to the rather
prejudicially named ‘problem’ of altruism. The free-rider problem sees no mention at
all within this book. Instead alliances are depicted as unproblematically synergistic
relationships, illustrated with cartoon amoeba smiling even as they ingest one another.
It is true that even after Margulis’ initially astonishing hypotheses have been
incorporated into mainstream orthodoxy, many biologists still view symbiosis as the
exception to the norm. But would moving symbiosis closer to the spotlight in
evolutionary writing really constitute the revolution that Meinesz heralds? Is
symbiosis at odds with the neo-Darwinian synthesis? As is common what we have
here is a difference of emphasis, presented as a difference in kind. It is true that
mainstream accounts of evolution focus on the accumulation and natural selection of
mutations. The question we must ask, however, is whether symbiosis constitutes a
phenomenon that contradicts, extends, or fits neatly within, this description. Most
authors would say that while symbiosis may constitute an evolutionary mechanism of
organism construction in addition to the selection of mutation, it does not undermine
or contradict traditional Darwinian selection. The problem is that the theoretical battle
fought between adherents of cooperation and mutualism and of competition and
survival of the fittest, is that the two sides were often misrepresented as sentimental
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utopians, on one side, and hard-headed realists on the other. The mundane truth
acceptable to all is that natural selection will favour alliance whenever it offers
synergistic benefits that cannot be acquired alone. The war of appropriate emphasis
then turns on the empirical question of how often such benefits exist, and the answer
increasingly looks to be: a lot. To this extent then Meinesz can be applauded for
seeking to secure a more central position for symbiosis within evolutionary theory,
but I fall short of calling such a change a ‘revolution.’
Religion
You can’t escape the religion in this book. Not only does Meinesz constantly refer to
it, but several chapters are specifically dedicated to evaluating science in the light of
belief and vice versa. One might accuse Meinesz of wanting to rewrite The
Ancestor’s Tale for theists. Like Dawkins he wants to make the deep of history of
life accessible and exciting for non-scientists, but without the atheistic vitriol for
which Dawkins has become famous. It is not a bad ambition, as I’m sure Dawkins’
name on the cover is enough to prevent many people who would benefit from it from
even opening The Ancestor’s Tale. Meinesz, a Catholic, wants to present
evolutionary theory as something compatible with religion and spiritualism, without
shrinking from the actual hard science. Unfortunately, he lacks Dawkins’ effortless
capacity for bringing science to vivid and colourful life in the mind of the reader. I am
happy to allow that I am not the believing layman at whom this work is aimed but I
still feel it is a shame that scientists feel the need to muddy their work by associating
it with all this metaphysical stuff on which they are not qualified to pronounce.
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Meinesz sets the tone of the book in chapter one when he talks about a friend’s
determination to retain ownership of land in which some of the oldest prehistoric cave
paintings are found. It is a metaphor perhaps for our common ownership of our past,
for Meinesz goes on to discuss the various creation myths and tries to emphasize that
whatever your beliefs, our past is a shared truth to which all of us remain connected.
He mixes palaeontology with bible stories in a way designed to emphasize our
fascination with our origins. He mostly presents the bible stories as just stories, while
the palaeontology is fact, but he demurs sufficiently to leave room for people not to
feel contradicted. He even presents the standard Catholic line about God inserting the
soul at some critical moment in evolution, by saying “Present-day knowledge would
surely have led the authors of Genesis to reserve for God alone the impulse to create
the soul.” (Meinesz 2008, 17) It is unsubtle word-weaselry. He doesn’t call it
science, but he mixes his religion in with his science sufficiently closely that only
prior knowledge allows the reader to easily tell them apart. Meinesz spends a long
time evaluating evidence for a large scale flood that could have served as the
inspiration for the biblical story of Noah and the Ark, about which I was tempted to
say ‘who cares’ leaving the reader to fill in the obvious answer. But maybe that’s
mean, maybe even ‘non-believers’ can find interest in the capacity that science gives
us to explore the origins of these undeniably important old myths.
Contingency is the issue that Meinesz keeps coming back to because he seems to view
it as presenting the biggest threat to a religious thought. He settles for Gould’s line
that if we reran the tape of evolution, we would see a radically different outcome, and
asks how much this non-teleological worldview threatens the way in which theists
view the ‘meaning of life.’ Meinesz also adopts Gould’s other position about science
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and religion being NOMA (non overlapping distinct magisteria) (Meinesz 2008, 116)
and he states that scientists should stick to their half of the two ‘Magisteria’ and keep
out of metaphysical debates that are best left to theists (even if he fails to take this
particular piece of advice himself). So while the scientific Magisteria rule that
evolution is fundamentally contingent and not goal-directed, this has no bearing on
the separate kinds of arguments that the spiritual magisterial are going to offer
regarding mankind’s purpose in life, or what we can expect to happen after we die. He
criticises intelligent design hypotheses for failing to distinguish these domains, for
letting the scientific picture be dictated to by religion. He claims that the religious or
spiritual domain ought to let science proceed by its own lights without intruding on or
feeling threatened by its discoveries.
Most people simply reject this proposed bifurcation. Atheists reject the idea that the
moral domain is only accessible by believers, while theists probably resent the idea of
having to survive on science’s leftovers. Meinesz puts the religious domain into a
subservient relationship with science that many theists would, I imagine, find hard to
accept. The onus is on religious leaders to adjust their views as science makes new
discoveries, not vice versa. Science and religion are not non-overlapping domains
because we don’t know what science will discover in the future so we don’t yet have a
properly delineated scientific domain. If this is the case then it is impossible for
religion to be sure it does not pronounce on something which science will later
contradict. Religion is condemned to play second fiddle, playing catch up.
Meinesz certainly is no apologist for creationists, and emphasizes that the bible is just
plain wrong about lots of things and that life really is just “the result of a long,
pitiless, random struggle for survival in the face of incessant arbitrary decapitations.”
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(Meinesz 2008, 193) Yet he doesn’t think this necessitates conversion to atheism, just
reinterpretation of scripture. “Ancient, divine messages can be adapted to modern
knowledge.” I’m really one of those atheists who would prefer ‘the faithful’ to be
proper full blooded believers or not at all. Talking about the need to reinterpret
religious texts while simultaneously asserting their truth and divinity seems like a
textbook recipe for trouble: at least literalists have a limited number of excuses at
their disposal. However Meinesz doesn’t present his religious views as justifying or
excusing anything. Ultimately he is trying to show that believing in evolution does not
force a person to become a non-believer. And he is probably right. Nonetheless, his
religiosity is bound to raise the hackles of anyone accustomed to finding wonderment
in nature without having to overlay it with a greasy coat of magical realism.
Origins of multicellularity
The move to multicellularity is a new genesis because, like Lego pieces, it provides a
new and unlimited way of constructing novel organisms by the addition of different
combinations of pieces in different ways. The creative power of multicellularity lies
in its modularity. Organisms can be created in cumulative stages, where each stage is
robust and can be added to without limit. Meinesz claims that the move to colonial
living was presaged by a change in life style – some organisms left the surface waters
of the oceans and settled on narrow ledges of continental shelf, where the water is
shallow enough that plenty of sunlight filters through. Here they faced a whole
different set of ecological challenges – no longer required to subfloat, they in fact
secured advantage by anchoring themselves to the floor of their hospitable new home.
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Much of this chapter is spent debating a single question – was the transition to
multicellularity a simple case of responding adaptively to a changed environmental
circumstances – i.e. to living on a shallow ledge (the “convergent evolution
hypothesis”). Or did the move from open water simply allow a pre-existing capacity
to develop and thrive where the previous environment did not favour it (the “shared
software hypothesis”). Meinesz places a lot of importance on comparing these
hypotheses. But what turns on whether those mutations happened before of after the
change in habitat? Even if multicellularity is a new life history trait that appeared in
response to a change of habitat, that trait was made possible by an underlying genetic
architecture (combined of course with various other epigenetic and environmental
conditions.) Probably a mutation, or a series of mutations, had to happen to that
architecture before multicellularity was available as a strategy. There are a few
reasons why Meinesz thinks it is important to distinguish between the rival
hypotheses.
Firstly, Meinesz sees the existence of multicellularity in multiple distinct lineages, but
not all lineages, as a fact in need of explanation. A trait such as flying is present
across multiple lineages, including birds and mammals. We say that this trait is
analogous, or has appeared by convergent evolution, because the evolution of flight in
bats took place long after the bat lineage separated from the bird lineage. On the other
hand, we say that possession of a vertebra is a homologous trait across vertebrates
because all vertebrates descend from a common ancestor that had a vertebra. Meinesz
thinks the existence of underlying homologous genetic architecture provides this
explanation, but analogy does not, because if multicellularity was an analogous trait in
distinct lineages then we should expect to find it in all lineages that have sessile
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lifestyles. Only the ‘shared software’ hypothesis can explain why some lineages
haven’t made the transition to multicellularity. This is too strong, because many
things that are evolutionary possibilities fail to happen. Dolphins and sharks have a
convergently evolved aquiline body form that helps them swim efficiently in water,
yet there are no fully aquatic marsupials. However, if the various lineages diverged
before any of them had acquired the mutation necessary for multicellularity, then we
have to suppose that the multicellular lineages all acquired the necessary mutation
independently, which Meinesz seems to think is less attractive on the grounds of
parsimony.
Another reason Meinesz has for advocating the shared software hypothesis is that
offers him a route to coherence with his preferred explanation for the appearance of
life on earth – panspermia. If some but not all organismal lineages possess some sort
of necessary genetic precursor to multicellularity, then Meinesz can say that those
lineages descended from different strains of alien bacteria.
Lastly, it seems that Meinesz prefers the shared software hypothesis because it allows
him to give a scientific explanation that is compatible with a theistic need for the
evolution of man to be inevitable. Meinesz claims that if multicellularity is the result
of some shared software, then “organisms were pre-programmed to become
multicellular when they became sedentary” (164) and multicellularity is a
deterministic phenomenon.
Meinesz wants to believe that multicellularity evolved simultaneously across all
lineages and only after the move to sedentary living, and that examples of
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multicellular organisms achieved their multicellular status via a single common
mutation or set of mutations. Yet the most up to date evidence suggests that
multicellularity appeared early and repeatedly, because of a confluence of
environmental, ecological and genetic factors. In a recent review, Rokas 2008 claims
that multicellularity is a heterogeneous trait across different lineages but that it first
appeared in filamentous cyanobacteria, appearing in the fossil record 2.5-2.1 bya.
Multicellular eukaryotes appeared soon after the appearance of eukaryotes, around 1.2
bya, with complex forms appearing 1.0-0.4 bya. Volvocine algae represent the most
recent invention of multicellularity, around 0.05 bya. It is obvious therefore that
complex multicellularity appeared neither rapidly nor simultaneously an all phyla.
Furthermore, Rokas says that “Not all instantiations of multicellularity are the same,
and they do differ in important details.” (Rokas 2008, 239) For example,
multicellularity in volvox likely evolved after incomplete separation after cell
division, whereas in Dictyostelium it is a result of aggregation. “Thus any expectation
that gene families participating in cell adhesion in the two lineages would show
similar trends would likely be unfounded.” (Rokas 2008, 239) It is now known that
Dictyostelium achieve multicellularity using a distinct array of genetic software from
the fungi, plants and animals (Williams et al 2005).
Research done on Volvocine algae also shows that volvocale multicellularity differs
from metazoan multicellularity precisely because they are underpinned by distinct
genotype-phenotype map structures. V. carteri achieve multicellularity using a gene
RegA to conditionally inhibit chloroplast production in some of their cells. These
cells are then prevented from growing to the size which triggers mitosis, and so are
restricted to somatic functions throughout the lifetime of the group. This rather crude
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way of achieving a division of labour prevents V. carteri from developing multiple
cell types and is offered as an explanation for why the volvocale transition to
multicellularity has not been followed by an explosion of diversity, as in metazoan
lineages (Nedelcu & Michod 2003, 2006). Other metazoans have achieved
multicellularity using a more complex series of mutations at the cellular level so that
different sizes of cell can be produced, and mitosis can be controlled by independent
factors such as cell signalling. The key to the hypothesis is an explanation for why
volvox ran up against these constraints, when other phylas did not. The answer lies in
a peculiarity of volvocine mitosis. While most metazoan cells divide by binary
fission, with one cell splitting to produce two, volvocales have multiple fission.
Binary fission allows you to incrementally increase cell size, for example. Multiple
fission means that mitosis of an adult cell reproduces a whole multicellular individual.
We can surely imagine similar sorts of constraints might block the possibility of
multicellularity altogether in some lineages, refuting Meinesz’ conjecture that only a
shared software hypothesis could explain the absence of multicellularity in these
lineages. On the other hand it has been found that most of the genetic toolkit
necessary for multicellularity in metazoan lineages is also present in unicellular
ancestors. Genes have mostly been co-opted rather than gained anew, though they
have often dramatically increased in number or gained new functions. Some
components however do seem to be genuinely novel innovations. The main genetic
changes concern genes responsible for regulating cell differentiation, cell-cell
signalling pathways and cell adhesion. In the evolution of animal multicellularity,
“gene machinery predated but was co-opted for multicellularity in the time antecedent
to the transition.” (Rokas 2008, 246) In fact if we look to the literature we find the
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most up to date consensus is that the whole bilaterian clade - i.e. all the different
animal phyla that evolved from a common sponge or cnidarian ancestor - share a
common genetic toolkit, including ancient hox gene clusters. Geneticists think that
duplications and modifications (tinkering) of these very old genes underpin all of the
modern body plans. The closest relatives of the bilaterians, the cnidarians and
sponges, show intermediate forms of multicellularity/coloniality and a range of sessile
and motile lifestyles.
Multicellularity is a homologous trait in some respects, and an analogous trait in
others. It is interesting to ask what was the relative contribution of extrinsic
(ecological and environmental) and intrinsic (genetic) factors in the origin of animal
multicellularity, but this does not amount to the dichotomy that Meinesz portrays. The
evidence therefore says that to some extent the software did predate the transition
(within this lineage) but to some extent new mutations were needed, as well as much
gene duplication and cooption of function. Meinesz may be overplaying the
importance of analogy versus homology here - the matter turns on common ancestry,
which is a matter of degree (Griffiths 2007 denies this, but on the alternative
developmental view of homology then multicellularity probably is not a candidate
homologue at all). All phyla have a common ancestor (probably, because they all use
the same DNA code) and homology and homoplasy are not sides of a dichotomy but
ends of a continuum, separated by varying degrees of modification, reflecting deep or
more recent ancestry (see Hall 2007). The final question then is why Meinesz or
anyone else should believe that securing one end or other of this continuum as the
explanation for a trait has any bearing at all on the meaning of life? Homology looks a
long way away from the kind of inevitability that theists really seek.
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The epilogue that ends How Life Began serves primarily as a call to arms. Scientists,
Meinesz declares, must leave their ivory towers and face the responsibilities of
dissemination and communication of knowledge. Biologists, in particular, have a duty
to guarantee a widespread appreciation of the beauty and fragility of the world we live
in. Whether or not I believe in life after death, I agree that biologists have a special
part to play in ensuring that there is life after tomorrow.
Bibliography
Gould, S. J.: 2000, The Lying Stones of Marrakesh: penultimate reflections in natural
history, Random House.
Griffiths, P. E.: 2007, The Phenomena of Homology, Biology and Philosophy 22:
643-658.
Hall, B. K.: 2007, Homoplasy and homology: Dichotomy or continuum?,
Journal of human evolution.
Nedelcu, A. and Michod, R. E.: 2003, Evolvability, modularity, and individuality
during the transition to multicellularity in volvocalean green algae, in G.Schlosser and
G. Wagner, (eds.) Modularity in development and evolution, Univ. Chicago Press,
Chicago.
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Nedelcu, A. & Michod, R. E.: 2006, The Evolutionary Origin of an Altruistic Gene,
Molecular Biology and Evolution.
Rokas, A.: 2008, The Origins of Multicellularity and the Early History of the Genetic
Toolkit for Animal Development, Ann. Rev. Genet. 42, 235-51.
Sapp, J.: 1994, Evolution by Association – A History of Symbiosis, Oxford
University Press, Oxford.
Williams, J., Noegel, A. & Eichinger, L.: 2005, Manifestations of multicellularity –
Dictyostelium reports in, Trends in Genetics 21, 392-398.
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