Evolution (organic).
The notion of Darwinian evolution of forms and entities, according to which all organic species
descend from a common ancestor through various processes among which natural selection is the
most crucial, forms the framework of current biological investigations. Although biology
underwent deep transformations and conceptual shifts since 1859, the initial formulation of this
modern idea of evolution is due to Darwin’s Origin of species. This promoted a new
interpretation of major biological concepts such as adaptation or function, and raised new
problems for researchers. The notion of biological evolution entails important consequences
regarding the idea of time, especially concerning the time of biological processes and forms, as
well as the use of temporal processes in biological explanations.
The first section will sketch the historical context of the rise of evolutionism. The second section
will explain the major concepts of biological evolution, according to the contemporary version of
Darwinism. The third section will then focus on some major controversies that recurrently
appeared in the history of evolutionary biology, concerning the process and the pattern of
evolution.
History of the idea of organic evolution.
The idea of an evolution of species traces back far prior to Darwin. However, he is the
father of modern evolutionism because he argued not only for a pattern of descent between
species – the Tree of life – but for a process likely to explain this pattern – natural selection.
Among prior tenets of what was called “transformism”, some 18th century writers like Robinet,
Benoit de Maillet, or later most famously Jean Baptiste Antoine de Lamarck, held versions of
evolutionism that explained evolution, yet through rather implausible mechanisms.
Several problems met by naturalists were reasonably stimulating biologists to conceive of
a general evolution of species. First of all, whereas big differences between species are obvious,
it is not so clear sometimes whether two individuals are of distinct species, or of distinct varieties
of one species. Therefore lots of classes held to be distinct species, hence distinctively created by
God, might turn out to be varieties of one single species. A mechanism would then account for
the derivation between them. Linnaeus, author of the most general system of classifying species,
and tenant of species as distinctively created by God (“fixism”), yet faced in this way the problem
of hybrids. His contemporary and rival Buffon defined a concept of species in terms of the ability
to interbreed and have fertile offspring, a concept that fared better than a purely morphological
concept of species like Linnaeus’s, but that was not generally applicable. Moreover, as Kant
famously explained in the Critique of Judgment, naturalists until the 19th century noticed more
and more frequently that the types of various species are often quite similar to one another, as if
for example all the vertebrates were variations on a same theme - what Goethe called “original
type”. Famously, Geoffroy Saint Hilaire in 1820 claimed that whereas the two major orders,
vertebrates and arthropods (like crustaceans) seem absolutely separate (as held his rival Cuvier),
they were variants of a same type, the arthropod living inside its spine and the vertebrate outside
of it. Therefore, several thinkers, particularly from the school of Naturphilosophie in 19th century
Germany, conceived of a general evolution of species from the simplest to the most complex
forms – though often a logical evolution of forms rather than a historical process - as an
explanation of this pattern of similarity.
Religion has obviously been an obstacle to accepting evolution. The Church said that the
earth was only 6000 years old, which makes quite unconceivable a process of transformation of
species, since at the scale of human civilization no one witnessed any such change. But this
difficulty, which was still precluding Buffon to accept explicitly evolution of species (even if he
would accept transformation of varieties) slowly vanished during the 19th Century, because,
among other reasons, of the discoveries of fossils of unknown animals and of the advancement of
geological theories of Earth. George Lyell, who was Darwin’s friend, wrote the important
Principles of geology (1830–33), which claimed that Earth could have been shaped several
millions years ago.
For those reasons, a general audience became more familiar to the ideas of evolution. Just
before Darwin, Robert Chambers wrote Vestiges of the Creation, a widely read book which
sketched a picture of the evolution of organic forms, without a scientific theory supporting it. At
the time, philosophers such as Herbert Spencer elaborated general theories of evolution, which in
general relied on a formal scheme of complexification. Before him, Lamarckism, the most
accomplished transformist theory before Darwin, appealed to two forces, the first one being
precisely complexification (which explains why in the same genus simple forms are likely to give
rise to more complex) and the second being “adaptation to circumstances” through inheritance of
acquired characters (this one is in general the only one people think of when they refer to
Lamarckism).
Evolution by natural selection is one nice example of simultaneous discovery in the
history of science: while Darwin, after a long journey on the Beagle, came to this idea through
reflections on the geographical distribution of species, on morphology, and on domestication, in
the same time naturalist Arthur Wallace had the same idea. This anecdote indicates that in the
1850s time was ripe for evolutionary theories. They presented their results in 1844 in a joined
meeting that anticipated the publication of the big book Darwin wanted to write patiently during
several years, and published in 1859, before revising it extensively along the five next successive
editions. The book is “one very long argument”, and whereas most chapters use arguments from
various field such as embryology, morphology, biogeography or paleontology, to support the idea
of evolution by natural selection, several other chapters are devoted to a rebuttal of objections
that Darwin foresaw: the lack of intermediary forms in the fossil record, the very complex organs
like eyes, the evolution of instincts, etc.
In general however, lots of biologists were convinced by Darwin’s demonstration of an
evolution of species. The general audience was more reluctant for religious reasons. However the
fate of Darwinism is more concerned with the reactions to the process hypothesized by Darwin to
account for evolution, i.e. natural selection. Darwin was indeed pluralist regarding the processes
generating evolution; he accepted for example Lamarckian inheritance of acquired characters.
The major question then was the relative impact of those several processes onto evolution, and
this is perhaps the main general issue that following biologists have to deal with.
What we call “Darwinism” might be born when German biologist August Weissmann,
working on heredity, conceived of a separation between the “somatic cells” and the “germinal
cells”, id est the characters proper to an individual (and likely to change) and the characters that
she inherited from her parents and passes to her offspring. This prevents any inheritance of
acquired characters and leaves natural selection as the most plausible general mechanism of
evolution.
The history of Darwinism in the 20th Century means first the Modern Synthesis, initiating
“neo-Darwinism” in the 30s. Briefly said, natural selection, according to Darwin, sorts
individuals that vary and have various offspring. The process of selection will occur no matter
how the variation is caused, so Darwin’s theory was neutral regarding an explanation of
hereditary variation (i.e. why all offspring of a couple of zebras are on the one hand alike - as
zebras – and different – as differing to some extent from their parents). But in the 1900s,
Mendelian genetics came into play. At first sight, genetics and Darwinism seem at odds, since
Darwin was talking of evolution through selection of small differences, whereas genetics treats
combinations of discrete characters, which seems non-gradual. Hence, a controversy opposed
Darwinians and Mendelians until the 20s. Then, Ronald Fisher, Sewall Wright and J.B.S.
Haldane showed by devising probabilistic models of the evolution of genetic frequencies in
populations (a field called population genetics) that, far from opposing Darwinism, the
Mendelian heredity is an explanation of heritable variation that makes natural selection necessary
and powerful. Mutation of genes and recombination during meiosis and fecundation (in the case
of sexual reproduction) provide the variation upon which selection operates. This synthesis
between Mendelism and Darwinism is the origin of today biology. Later, such synthesis extended
to systematics (with Ernst Mayr), paleontology (with George Simpson), etc. However, the
preeminence of population genetics in the modern account of the processes of evolution entailed
that evolution is now conceived of as the “change of genes frequencies in a population”, whereas
the first Darwinians were thinking, more loosely, in terms of change of organic forms.
Darwinian evolution
The concept of natural selection
Darwin thought of natural selection as the result of “struggle for life”: since the resources are in
general rare in an environment, and since the rate of increase of a population exceeds in general
the availability of resources (an idea that he famously took from Malthus’s Essay on the Principle
of Population, 1798) it follows that only the ones who are better equipped to get resources will
survive and reproduce, being then likely to pass those abilities to their offspring. The frequency
of those traits supporting those abilities increase, and this continued process, on the long run,
explains a general change of the type of the species, which finally leads to a novel species (some
individuals being so different than the initial ones, or so distant, that they could not interbreed
with them any more). More concretely, this competition (mostly between members of a same
species) consists in getting food, sexual partners, and escaping predators.
A more abstract formulation of natural selection, less tied to this biological case, can be
given. Following Richard Lewontin, any population of individuals satisfying three conditions will
undergo natural selection : those individuals vary regarding some traits (variation); they have
offspring that do vary from them and between one another, in a way that the variation between
offspring and the mean of the population positively correlate with the variation between their
parents and the mean of the population (heritability); and those properties according to which
they vary are relevant in their expectation of having some number of offspring. (If several
organisms replicate and vary, but that the properties transmitted have no consequences upon their
probability of reproduction, there will be no selection at all.) With this third property we can
define “fitness”. Whereas still intuitive for Darwin when he talked about “survival of the fittest”
(following Spencer, and wanting to reject any intentional connotation of the word “selection”),
“fitness” is now a technical term which means both survival and expectancy of offspring.
Defining the fitness of a trait implies assuming that this trait somehow correlates with the
offspring expectancy.
[Fig. 1. Diagram of a selection process in neo-darwinism, about there.]
What the selected individuals really are, their nature, is not relevant in this formulation.
Hence there logically can be selection on organisms, which was what Darwin thought of, but also
on groups, on species, and, at a lower level, on genes. One of the most debated question in the
philosophy of biology, indeed, is the “units of selection” controversy, namely the question of
what, among those kinds of things, are the ones onto which selection takes place. George
Williams in Adaptation and natural selection (1966) convincingly argued that selection
apparently acting on groups - for example altruist behaviors that seem to increase the well being
of the group while threatening the organisms that achieves them - can in fact be explained in
terms of selection acting on individuals (organisms or genes). After William Hamilton, biologists
call “kin selection” a selection acting on one gene carried by several individuals: selection will
retain an organism that acts against its “interests” if the consequences can favor one of its kin.
On this basis, Richard Dawkins argued that natural selection indeed acts upon genes rather than
organisms. Genes do “replicate” - they are “replicators” in Dawkins’ language - but the rate at
which they successfully replicate depends upon the interactions between organisms that they
contribute to shape. Thereby, philosopher David Hull suggested another formulation of selection:
natural selection is the process according to which “replicators” differentially reproduce due to
the interactions of entities named “interactors” (in the usual case of biology, it is the organisms).
This formulation allows one to realize that natural selection could occur about various objects to
the extent that they “replicate”, for example Dawkins talks of cultural selection, because cultural
entities seem to replicate.
Explaining through natural selection
The diversity of species (in time and in space, for example: why are there kangaroos in
Australia but not in South America?) and the adaptation of organisms to their environments, are
explained through Darwinian evolution. First, the taxonomy of species receives a historical
interpretation. The only diagram in The Origin (Fig.2) represents a pattern of branching between
species, or genera, or any biological taxon. All the taxonomic relations (being part of a same
genus, etc.) were reinterpreted by Darwin in terms of history: the closer two species are in a
morphological taxonomy, the closer they are in the temporal sequence of evolution.
[Fig.2. Darwin’s diagram of evolution, about there.]
Concerning adaptation, the old explanation referred to the divine will or a providence that
would account for the amazing fit between organisms and their environment – for example, the
beak of species of finches that fits to the depth of the holes within which they chase insects. The
Darwinian explanation of adaptation is natural selection: such process obviously led to the fit of
the beaks with the holes – and in the same time to the divergence of the Galapagos finches into
several species, all being specialized in one kind of holes, and characterized by one length of
beak. This Darwinian example illustrates how natural selection accounts in the same time for a
process of diversification of species and for adaptation.
Philosophically speaking, natural selection provides also a way to escape the suspicion of
teleology that constantly assaulted biology. Modern natural sciences exclude explanations in
terms of intentions or goals, because by principle nature has no desires. However, talking of
functions of organic parts means that those parts are here in order to do such and such: such
proposition seems teleological. Although not really embarrassing for biologists, this problem
puzzled philosophers of science – especially, since the times when funding science on theology
was not admitted any more. Typically, Kant devoted half of the Critique of Judgment to the
problem of legitimizing teleological judgments in life sciences without appealing to a Creator.
Yet in the Darwinian framework, functional statements do not object to naturalism: philosophers
Larry Wright and Ruth Millikan suggested to interpret “the function of X is Z” by “X has been
selected because it was doing Z”, which does not appeal to any transcendent intention. Natural
selection might legitimate the functional talk traditional in biology.
Evolutionism within biology
Proximate and ultimate causes.
The emergence of evolutionism entailed a whole transformation of biology. During the
rise of molecular biology, after Watson and Crick’s discovery of the DNA as the substance of
genes (1953), Ernst Mayr reflected upon the Synthesis to which himself contributed. He argued
that causal explanations in biology can take two forms: proximate and ultimate. Proximate causes
are the processes and events that cause a feature in the life of organisms, e.g. the “genetic
program” of some bird accounts for its migrating behavior and the physiology of its muscles
accounts for the way it flies. Molecular biology, physiology, biochemistry, embryology, all
unveil proximate causes and constitute “functional biology”. The other part is “evolutionary
biology”, and aims at accounting for why the organism is likely to be the way it is, e.g. it searches
for the evolutionary history which led to the genetic program embodied by the migrating bird.
Those “ultimate causes” of course extend far prior the existence of the organisms or species
considered. Paleontology, behavioral ecology, ecology, systematics, population genetics,
constitute the main disciplines of this “evolutionary biology”. Mayr added that whereas
“proximate causes” amounts to explanations of the same kind than those usually found in physics
and chemistry, “ultimate causes” require another kind of explanation, since they mostly rely on
natural selection and have to integrate knowledge of history as a background condition. This
makes of course evolutionary biology the core of biology, upon which relies the specificity of
biology regarding other natural sciences. This implies that biology has an irreducible historical
dimension, contrasting with lots of natural sciences which search for unhistorical laws or
correlations, striving only for what philosophers after Ernst Nagel call “nomothetic
explanations”. Moreover, most of the conditions of evolution are themselves product of evolution
(for example, the process of fair meiosis assumed by all the Mendelian rules.) The science of
organic evolution therefore required that scientific explanation consist also in depicting
contingent temporal processes.
Form and function.
In 1916, historian E.S. Russell published Form and function, an important book revisiting the
history of biology as a fight between two general approaches of living phenomena: focusing on
functions, or being interested in forms. Those features, forms and functions, are obviously proper
to living beings (brute matter does not display transmitted forms). Russell saw the famous debate
that opposed Cuvier and Geoffroy Saint Hilaire at the Museum (Paris) in 1830 as one major
episode in this longstanding debate. Geoffroy, arguing in favor of one general type of organisms
realized in all orders, was a tenet of form-biology, while Cuvier was mostly interested in
functions, and called “principle of the conditions of existence” the principle according to which
all functions in an organism have to be feasible and compatible. For this reason, because one
could not change one function without altering the whole and then making the organism unable to
fulfill the principle of conditions of existence, Cuvier opposed Lamarck’s gradual transformism.
On the other hand, for Geoffroy the general types are only fine-tuned by local adaptations, but
their main morphological rules are something universal in the living realm, hence not connected
to specificities of the various environments within which various species came to life: for this
reason, adaptation can not account for those rules. The spine, for example, pervasive across all
order of organisms, exemplifies such a formal feature.
In The Origin, Darwin considers this debate from the viewpoint of evolution by natural
selection. He admits that there are two most general principles of biology: the one of “conditions
of existence” (i.e. Cuvier’s) and the one of unity of types (i.e. Geoffroy Saint Hilaire). He
inquires into their connection, namely whether functions of organisms, shaped by natural
selection, are the main factor accounting for the various features of the species, or whether some
general formal features, independent of the successive environments of organisms but historically
transmitted, are the major constraints on the history of life. He answers that the principle of the
conditions of existence resumes to natural selection, whereas unity of type specifies the stable
persistence of organic forms. However, because those inherited forms are themselves constituted
through evolution by natural selection, those types in the end rely on the action of natural
selection and the “unity of type” gets subsumed under the other principle. This means that
Darwinian biology subordinates form biology to function biology.
Major longstanding issues in evolutionary biology.
Issues relevant to the process of evolution
Even if selection is acknowledged as one of the main cause of evolution - Lamarckian evolution
being excluded - other mechanisms have been conceived of by biologists. One classical
formulation of the question of evolution in population genetics is analogous to mechanics, as
argued by philosopher Elliott Sober in The nature of selection (1984). Considering some varying
traits in a population, geneticists first write the equations that would rule the change of gene
frequencies in a pure Mendelian case with no selection, no mutation and no migration - called the
“Hardy-Weinberg equilibrium”. Then they compare to the actual case. Any deviation from the
expected equilibrium frequencies should have a cause, possibly natural selection. Yet, Sewall
Wright in the 30s showed that in small populations a kind of sampling error occur which can lead
to the fixation of some genes independently of their selective value. This “random drift” would
disappear in infinite populations, but since real populations are always bounded, random drift
surely matters in the actual evolution of gene frequencies.
Thus, apportioning the causes of evolution, especially selection and drift, is a constant
problem faced by population geneticists. Several important controversies in the course of
evolutionary biology revolved around such issue. At the origin of the Synthesis, Fisher argued
against Wright about the role of drift. If drift is important, as claimed Wright, mean fitness of
populations is not always maximized, whereas Fisher opposed a mathematical formula he proved,
the “fundamental theorem of natural selection”, meaning that mean fitness necessarily increases
until the exhaustion of genetic variance. Deciding this point implies an empirical knowledge of
the size of natural populations. Later, the question involved an investigation of the reasons of
genetic variability – “polymorphisms” - in populations. Biologists like Dobzhanski and Müller,
among others, forged theories to account for this maintenance. Afterwards, Motoo Kimura
vindicated the so called “neutralist theory of evolution”, claiming that most of the evolution at the
level of nucleotides (the molecules composing the DNA) is neutral, due to drift, because most of
the mutations of nucleotides are selectively neither advantageous nor deleterious. Although
theoretically important, this theory does not truly oppose Darwinism since it is only concerned by
the molecular level, and leaves intact the idea that the evolution of genes themselves and of
phenotypes is due to selection. However, the neutralist theory emphasized that evolution is a
constant process occurring at many levels according to various mechanisms.
It is often difficult to consider evolution of one population of one species, because
ecologically the fates of several species are tied - each one defining selective pressure for the
others. Cases of parasitism, of mutualism, etc., belong to a general study of “coevolution”, for
example between figs and wasps, ants and plants, or of course men and intestinal bacteria, that
accounts for innumerable features of the organic world.
Other important controversies arise when we turn our gaze from “microevolution”, which
concerns rather short time scales and not-too-changing environments, to “macroevolution”, or
evolution at a higher level, concerning for example the appearance of new classes of organisms.
It has been debated since the founding fathers of the modern synthesis whether macroevolution is
microevolution at a larger scale or whether it requires novel principles. Simpson and Mayr for
example defended the former position, because they thought that an appeal to novel principles,
for example “macromutations”, would threaten Darwinism itself. Some biologists nevertheless,
like Stephen Jay Gould, Nils Eldredge, Elisabeth Vrba or Sean Rice will consider natural
selection of species. In those cases, the properties selected (for example the geographic range of a
species, the genetic variability, etc.) are properties of the species itself, unlike the mechanisms
accounting for microevolution, that have all to do with traits of individuals.
But the main challenges concerning this question of macroevolution came recently from
evolutionary theory of development or Evo-Devo. In microevolution, actually, natural selection
shaping adaptations for some functions is plausibly the main cause of evolution. This exemplifies
the Darwinian bias in favor of function biology. However, in The changing role of the embryo in
evolutionary biology (2005) Ron Amundson argues that the tenants of form biology constantly
opposed this Darwinian demonstration of the supremacy of function-biology. Their challenge
gets now much more consistent because they invoked some novel style of laws of forms that
scientific investigation has been pinpointing for three decades. Briefly said, neodarwinians
thought that mutation (and recombination) forms the material for natural selection. They
separated two ideas traditionally joined: inheritance (namely transmission of characters from
parents to offspring) and development (namely the ontogenetic process of an individual).
Selection acts on traits, no matter the process through which the individual came to display those
traits, so development seemed relatively external to evolution. Yet, some developmental theorists
emphasized that development can both constrain variations, and provide variations only by
changing the rhythm or order of the process, as Stephen Jay Gould summarized this in his
classical Ontogeny and phylogeny (1977). Evo-Devo researchers contend that the changes
relevant to macroevolution, for example “key innovations” like the wing of insects, the
thermoregulation system of mammals, etc., involve the effect of developmental constraints, and
are not understandable solely as effects of natural selection acting on punctual mutations in the
DNA. (But for them evolutionary theory is therefore more concerned by explaining across-taxa
features, like the vertebrate limb, rather than change within taxa and thus adaptations.) This
debate is obviously related to the set of problems posed by the understanding of the phylogenetic
pattern in general.
Issues relevant to the pattern of evolution.
The Tree of life raises three types of questions, both crucial to current evolutionary biology: the
shape of evolution, its orientation, and finally its origins.
Gradualism and discontinuities. For Darwin, evolution of the species was a gradual branching
process. Neo-Darwinism emphasized the gradualism, since variation would rely on small
mutations. For this reason, Neo-Darwinism has constantly been puzzled with discontinuous
evolution, for example “key innovations”. In the 70s, paleontologists like Stephen Jay Gould and
Nils Eldredge challenged the general gradual view of phylogeny, arguing that changes in
evolution display a discontinuous pattern : a fast (at the geological timescale) burst of novelty,
and a very long period of “stasis”, where one notices only minor modifications possibly due to
adaptation to local conditions. This theory of “punctuated equilibria”, albeit neutral regarding the
mechanisms of evolution, does nicely fit with theories from Evo-Devo (held by Gould), which
contrast very big changes relying on transformations in developmental processes with minor
changes due to selection on point mutations. This issue mostly rests on the interpretation of the
fossil record: Darwin claimed that its lack of transitional forms was due to geological reasons,
whereas tenets of “punctuated equilibria” claim that the record is, as such, quite reliable, and
constitutes an evidence for the stasis-burst schema of macroevolution. In this case, macroevolution would not be easily reducible to mechanisms of micro-evolution, and Neo-Darwinism
in general - since its core is population genetics – would have to be qualified. The emergence of
the most general plans of organization - for example the one taking place in the Cambrian and
explaining most of the extant phyla – is not accountable solely by micro-evolutionary principles.
In 1995, John Maynard Smith and Eors Szathmary initiated a theory of the ”major
evolutionary transitions”. Those are the fundamental events in evolution, through which the
forms of inheritance and replication changed. Replicating macromolecules, single cells,
multicellular organisms, social organisms and organisms with language are the steps of this
evolution. Each time, natural selection both contributes to the transition and becomes changed
through it, because new selectable entities arise. In this perspective, evolution by natural selection
is not absolutely tied to genes or life, and extends from molecule to talking beings. Such a
globalised theory casts a new light on the problems of discontinuity in the mere history of life.
“Cooperation” between entities, e.g. genes in chromosomes or insects in colonies, is a pervasive
pattern of explanation of those transitions, and requires understanding how natural selection
could favor cooperative behaviors while selfish defection would be at first sight selected for.
Direction. A common view of evolution sees it as oriented towards greater perfection and
achievement. Yet this is precluded by the very logics of Darwinism, for which natural selection
optimizes populations regarding their environments – hence, two organisms of two different
species, belonging to different environments, cannot be compared or considered as stages of a
continuous improvement. In the same time, it is difficult not to notice in a given branch of the
Tree of life, for example the vertebrates or the mollusks, trends of increasing complexity :
diversification of functions, finessing of detecting devices, increase of some quantities related to
the size of genes, etc. Darwin himself was ambiguous regarding this issue: while opposing the
notion of absolute perfection, he was led by common intuitions about progress in evolution. The
major conceptual issue however is still to figure out a concept of complexity likely to capture
those contrasted intuitions. Biologist Dan Mac Shea has shown in recent papers that a
“complexity” thought in pure formal terms (diversity of parts with no functional considerations)
makes visible some phylogenic trends in increasing complexity. This notion is yet far from the
intuitive one and it seems then that no theory could decipher in the history of life this constant
progress culminating in human species that we ordinary believe in.
Origin. Evolution by natural selection commits one to say like Darwin that all forms of life came
from one single organism (which of course irritated all religions). The fact that all species share a
same genetic code is nowadays another evidence of this single evolutionary history. From a
Darwinian viewpoint, the question raised here is the genesis of an entity satisfying the conditions
of natural selection. This problem involves both chemists and paleontologists – people seeking
traces of what happened and people conceiving processes that could have happened. Besides,
within evolutionism questions of origins are crucial: origin of sexual reproduction (why
consenting to pass on only 50% of your genes to the next generation, while asexual reproduction
does 100%?), origin of mind and culture. Whereas no theory is still satisfying, clearly natural
selection plays a fundamental role in those events.
See: DNA; Extinction; Darwin, Charles; Origin of life; Evolution, cultural; progress; fossil
record; Tree of life, Gradualism versus saltationism; Paleontology
Philippe Huneman. Institut d’Histoire et de Philosophie des Sciences et des Techniques (CNRS/
Université Paris I Sorbonne), Paris.
Further readings.
Arthur, W.. The origin of bodyplans.
Brandon, R. (1996) Adaptation and environment. Cambridge: MIT Press.
Dawkins, R. (1982). The extended phenotype. Oxford: Oxford University Press.
Eldredge, N. The unfinished synthesis.
Gayon, J. (1998) Darwinism’s struggle for survival. Cambridge: Cambridge University Press.
Gould, S. J. (1980) The panda’s thumb. London: Penguin.
Hodges,J.& Radick G. (eds.) (2003). The Cambridge Companion to Darwin. Cambridge:
Cambridge University Press.
Kimura, M.. The neutralist theory of evolution
Lewontin, R. Evolutionary genetics.
Maynard Smith, J. & Szathmary, E. (1995). The major transitions in evolution.
Mayr, E. (1961) “Cause and effect in biology.” Science, 134: 1501-1506
Mayr E. & Provine W. (1980) The evolutionary synthesis. Perspectives on the unification of
biology. Cambridge: Harvard University Press.
Michod, R. & Bernstein H.(eds.) Evolution of sex.
Michod, R. (1999) Darwinian dynamics. Oxford: Oxford University Press.
Richards, R. (1992) The meaning of evolution. Chicago: University of Chicago Press.
Odlin-Smee J., Laland K. & Feldman M. (2003). Niche-construction: the neglected process in
evolution. Princeton: Princeton University Press.
Sloan, P. (2005) “Evolution” Stanford Encyclopedia of Philosophy on-line.
Sober, E. (1984) The nature of selection. Cambridge: MIT Press.
Williams, G.C. (1992) Natural selection: domains, levels and challenges. Oxford: Oxford
University Press