Evolutionists Quotables

These are quotes drawn from either peer-reviewed papers in mainstream journals, or from published works by evolutionists.  This page will be frequently updated as we continue our reading. We will not quote creationists on this page. If someone is quoted here, they are an evolutionist, at least they were when they wrote the quote.

Mayr, Ernst Animal Species and Evolution The Belknap Press of Harvard University: Cambridge, MA 1965.

“The theory of evolution is quite rightly regarded as the greatest unifying theory of biology.” Pg 1

“We now believe that mutations do not guide evolution; the effect of a mutation is very often too small to be visible. Recombination produces far more selectively important phenotypes than does mutation and the kinds of mutations and recombination’s that can occur in a given organism are severely restricted.” Pg 8

“It was Linnaeus’ insistence on the constancy and objectivity of species that posed the problem of the origin of species, a problem previously nonexistent in that form.” Pg 13

“With increasing frequency since then, interbreeding has been considered a decisive criterion in species definitions.” Pg 15

“Indeed the most characteristic attribute of a species in such a non-dimensional system is that it is separated by a gap from other units in this system.  The gap that surrounds a species is the core of the species concept.” PG 18

“A population is a species only with respect to other populations. To be a different species is not a matter of difference but of distinctness.” Pg 19

“Species are “groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups.” Pg 20

“Actually the breaks in the fossil record are so frequent that it has been possible in only a few cases to piece together unbroken lineages connecting good species.” Pg 24

“The mere fact of exclusion does not prove that it is the result of selection in favor of avoiding competition. Other explanations may apply in certain cases.” Pg 72

“Which species reaches a given island first is presumably a matter of accident in many cases; yet once established it prevents colonization by newcomers. ….The numerical advantage of the early colonist is decisive.” Pg 73

“Invading species only rarely displace a native species from its niche. In most cases they occupy at least in part what appears to have been a previously unoccupied niche…Whenever a local biota can be enriched, this proves to me de facto that vacant niches had existed.” Pg87

“Species recognition, then, is simply the exchange of appropriate stimuli between male and female, to ensure the mating of conspecific individuals and to prevent hybridization of individuals belonging to different species.” Pg95

“The incompatibilities of courtship can be observed especially well when, in captivity, the male of one species is brought together with the female of a different species, neither having any choice of sex partner.  In such cases, it can sometimes be observed that the courtship is broken off again and again, in spite of a strong sex drive of both display partners, because one partner, (usually the female) does not respond properly to a stimulus given by the other partner. Under natural conditions, this would be the end of the courtship.” Pg 101-102.

“Successful hybridization is indeed a rare phenomenon among animals.” Pg 133

“With adequate tests it can be shown that indeed no two individuals of a sexual species are genetically identical.” Pg 164

“This contradiction worried Darwin and the early Darwinians considerably. Since they considered inheritance to be blending, they had to assume that, owing to blending, one-half of the total variability would be lost in each generation. At the same time, the availability of an inexhaustible supply of genetic variation was one of the cornerstones of Darwin’s theory. These two assumptions were completely in opposition to each other. There seemed only one answer to this conundrum, a truly colossal rate of mutation.” Pg 165

“Admittedly, mutations producing drastic changes of the phenotype are rare and any tendency to produce such mutations would certainly be selected against very strongly.” Pg 173

“In contrast, it is held by contemporary geneticists that mutation pressure as such is of small immediate evolutionary consequence in sexual organisms, in view of the relatively far greater contribution of recombination and gene flow to the production of new genotypes and of the overwhelming role of the selection and the prevailing epigenotype in determining the change in the genetic composition of the populations from generation to generation.” Pg 175-176

“Mutation pressure as a determinant of evolutionary change is of negligible importance in such organisms. Such types rely for evolutionary plasticity on the storage of genetic variation and the production of a great diversity of genotypes by sexual recombinations. At the other extreme are microrganisms. They owe their evolutionary plasticity to an ability to keep up with their changing environment largely by mutation.” Pg 180-181

“I believe that most currently existing forms of asexuality are secondary. Organisms would not have relinquished sexuality to such a large extent if it had not been advantageous to do so, and thus favored by natural selection.” Pg 181

“Natural selection, being a statistical phenomenon, is not deterministic; its effects are not rigidly predictable particularly in a changeable environment.” Pg 184

“Although much of the genetic variation in populations is due to this lag between the input of genetic variation in populations and its elimination by natural selection, there is evidence that some of the genetic variation is directly maintained by natural selection. We call this portion of the genetic variance “selected heterozygousity”.  Pg 221

“Each local population is the product of a continuing selection process. By definition, then, the genotype of each local population has been selected for the production of a well-adapted phenotype. It does not follow from this conclusion, however, that every detail of the phenotype is maximally adaptive.” Pg 311

“A subspecies is an aggregate of local populations of a species inhabiting a geographic subdivision of the range of species and differing taxonomically from other populations of the species.” Pg 348

“The interbreeding of two previously isolated populations in a zone of contact has been designated allopatric hybridization.” Pg 369. (Mayr understandably doesn’t like using hybridization for in species breeding. Propose new word?

“The biological species is usually also a morphological species (except for a few sibling species); the multidimensional polytypic species is nondimensional at any given place or time. Indeed species of animals on the whole are a singularly uniform phenomenon.” Pg 400

“Natural selection is considerably curtailed when so few genotypes are available for choice.” Pg 416

“it appears that the range of outbreeding is far greater in plants than in animals, at least in higher animals.” Pg 420

“The fact that the organic world is organized into species seems so fundamental that one usually forgets to ask why there are species, what their meaning is in the scheme of things. There is no better way to answer these questions than to try to conceive of a world without species.  Let us think, for instance, of a world in which there are no species, but only individuals, all belonging to a single “connubium”. Every individual is different from every other one in varying degrees and every individual is capable of mating with those that are most similar to it. In such a world, every individual would, so to speak, the center of a series of concentric rings of increasingly more different individuals. Any two mates would be on average rather different from each other and would produce a vast array of genetically different types among their offspring. Now let us assume that one of these recombination’s is particularly well adapted for one of the available niches.  It is prosperous in this niche, but when the time comes for mating, this superior genetic complex will inevitably be broken up. There is no mechanism that would prevent such a destruction of genetically superior combinations. The significance of the species now becomes evident. The reproductive isolation of a species is a protective device against the breaking up of its well-integrated, coadapted gene system Through organizing diversity into species, a system has been created that permits genetic diversification and the accumulation of favorable genes and gene combinations without any danger of destruction of the basic gene complex.” Pg 422-423

“It (speciation) is compatible with the story of creation in the book of Genesis.” Pg 429

“Polyploidy is widespread among plants and is one of the important mechanisms of speciation in the plant kingdom.” Pg 440

“Polyploids pose a difficult taxonomic problem. An autopolyploid may be virtually indistinguishable, at the time of origin, from the parental diploid.  Such a form is often referred to as a “polyploid race”…Yet such a “race” is reproductively isolated from the parental species and is, biologically speaking, a good species. This is another illustration of the frequent conflict between a morphological and a biological species concept.” Pg 448-449

“Actually, natural populations are highly heterozygous and composed of genetic environment that favors heterozygousity.” Pg 479

“The cases of circular overlap are considered by evolutionists as evidence for “speciation by distance”. “ Pg 512

“The important point is that different species are different systems of gene interactions or different epigenetic questions.” Pg 544

“It appears probable that speciation proceeds slowly, all other things being equal, in absence of genetic revolution.” Pg 581

“The picture of random mutations (mostly deleterious at that!) as prime movers of evolution and the typological flavor of the one-gene-one-character-one selective-value- theory were certainly a poor basis on which to interpret macroevolution.” Pg 612-613

“ And speciation, the production of new gene complexes capable of ecological shifts, is the method by which evolution advances.  Without speciation, there would be no diversification of the organic world, no adaptive radiation, and very little evolutionary progress. The species, then, is the keystone of evolution.”Pg 621

Jerry A. Coyne and H. Allen Orr Speciation Sunderland, MA: Sinauer Associates Inc. 2004.


Mayr’s “biological species concept” identified species as groups of interbreeding populations that are reproductively isolated from other groups.” Pg3

We conclude Chapter 1 by considering why species exist at all: Why do organisms form discrete clusters instead of an organic continuum? This is, we believe, one of the most intriguing unsolved problems of evolutionary biology.” Pg7

“Still others consider the gradual nature of speciation as evidence against the distinctness of it’s products….We contend, however, that the process of speciation is likely to be short relative to the duration of well-demarcated species and that brief transitions between long lasting and discrete entities do not make those entities unreal.” Pg11

“We will conclude that species are indeed discrete in sexually reproducing organisms, probably discrete in asexually reproducing organisms, but often not discrete in organisms that reproduce both sexually and asexually.” Pg 12

“It is well known, for example, that morphological discontinuities almost always coincide with genetic discontinuities in DNA sequences. This consistent carving of nature at the same joints is a powerful argument for the reality of species.” Pg 14

“Although most biologists agree that species are real, we lack rigorous studies needed to convince skeptics that nature is discontinuous.” Pg 25

“Evolutionists now appreciate that no single species concept can encompass sexual taxa, asexual taxa, and taxa having mixed modes of reproduction.” Pg 26

“In our view, distinct species are characterized by substantial but not necessarily complete reproductive isolation.” Pg 30

“In sexually reproducing organisms, the stable coexistence of genetically distinct groups in sympatry requires reproductive barriers between them.” Pg 31

“Fusion of species through hybridization contradicts Mayr’s view that speciation is not complete until it is irreversible. We cannot predict whether future environmental or genetic changes will undo reproductive isolation that is now “complete”.” Pg 38

“When one moves to fully sexual groups, one again finds discrete clusters of genes and traits. This is a clue that sexual reproduction itself must play a role in distinctness. In fact, we suggest that in sexually reproducing groups it is reproduction itself, combined with differential adaptation and the existence of tradeoffs, that ineluctably produces species.” Pg 53

“…every (species) concept requires comparing different groups of individuals, whether this comparison involves reproductive isolation, morphological distinctness or phylogenetic relationship.” Pg 55

“Given that isolating barriers act sequentially, prezygotic barriers will almost surely be the strongest current impediments to gene exchange.” Pg 65.

“The fact that postzygotic barriers act late in the life cycle does not mean that they were insignificant during speciation. Indeed there are several reasons to think they may be important:”  Pg 66

“Although such studies can tell us which reproductive barriers were important in individual speciation events, they cannot necessarily be extrapolated to other species, even within the same group.” Pg 70

“If such a disturbance destroys an isolating barrier, causing two previously isolated species to fuse into one (or into a hybrid swarm), one can infer that that barrier was important in speciation.” Pg 70-71

“Although diversification rates involve both speciation and extinction, we will suggest a way to infer those features of organisms that enhance the rate of speciation per se. We find two such features: animal pollination of plants, and traits associated with sexual selection in birds and insects. These observations suggest that behavioral and pollinator isolation are associated with speciation.  Such associations further imply that these isolating barriers were primary factors in speciation. If these barriers arose after reproductive isolation was complete, they would not be associated with higher rates of speciation.” Pg 81-82

“Both theoretical and biological considerations imply that parapatric speciation is more common than sympatric speciation, yet it is harder to rule out allopatry in the former case.”  Pg 84

“Our rationale is that biogeography can limit the nature and strength of evolutionary forces potentially causing reproductive isolation.” Pg 85

“A ring species encircles a geographic barrier, such as a mountain range or plateau. Populations around the ring appear to show free exchange of genes except at a single location, where adjacent populations are reproductively isolated.  Ring species are said to form when a single ancestral population gradually expands its range around the barrier. During this expansion, populations exchange genes with their neighbors, but gene flow is low between more distant populations, allowing them to differentiate more extensively. The two populations that finally meet when the ring is closed have been genetically isolated for so long that they have achieved strong reproductive isolation.” Pg 102

“But do ring species really exist? A convincing case must meet several criteria. First, there should be historical information that the ring was founded by one population rather than sever genetically distinct populations, and that all individuals around the ring descend from this ancestral population. At least one of the terminal populations must represent the most recent range expansion. There must be no geographic barriers that interrupt gene flow around the ring, and such barriers must not have existed in the past. Finally, one must be able to show that gene flow is fairly excessive between adjacent populations but decreases with distance around the ring. Unfortunately, every proposed ring species fails to meet one or more of these criteria.” Pg 103

“Given fluctuations in climate and geology over time, the present ranges of most species probably bear little relation to their ranges in the past.” Pg 116

“Single species often show morphological or genetic changes at transitions between habitats.” Pg 121

“Sympatric speciation also appealed to those who shared Darwin’s belief in the omnipotence and creativity of natural selection.” Pg 126

“Mayr’s critique had an immense effect on the field: evolutionists no longer considered sympatric speciation the norm or even very common.” Pg 126

“As characterized by Mayr (1963), sympatric speciation involves the evolution of reproductive isolation within the average dispersal distance (“cruising range”) of a single individual. Sympatric speciation thus differs from parapatric speciation, in which inbreeding is initially restricted by distance.” Pg 126

“Our analysis below leads us to conclude that, while sympatric speciation is theoretically plausible, and supported by both laboratory work and observations from nature, there is little evidence that it is common. In fact there are only a handful of credible examples.” Pg 127

“Consider two species of host-specific insects adapted to the fruits of their respective plants. If the hosts bear fruits at different times, preventing contact between adults of the two species, this constitutes temporal isolation­­-a prezygotic barrier. But if the fruits appear simultaneously, the insects may hybridize. If the hybrids perform poorly on either fruit, they suffer a form of postzygotic isolation: extrinsic hybrid variability.” Pg 181

“of all reproductive isolating barriers, postzygotic isolation most starkly reveals the problem posed by speciation to Darwinism: How could natural selection allow-much less favor-the evolution of unfit offspring?” Pg247

“Darwin realized that he asked his readers to believe both that most evolution is due to natural selection and that this evolution routinely yields species that produce unfit hybrids.” Pg 247

“…polyploid speciation is instantaneous, sympatric, and may often involve population bottlenecks.” Pg 322

“Evolutionary theory is not, at least usually, in the business of telling us what is, and is not biologically possible, a matter that depends on the particular suite of assumptions made. Rather, evolutionary theory tells us what does and does not follow from a given set of verbal assumptions. “  Pg 375.

“But the fact that taxa do not presently hybridize does not mean they did not do so in the past.” Pg 378

“We conclude that, while one can estimate biological speciation rates in a few groups, there are currently too few data to do this in most taxa.” Pg 412

“…the ideal speciation rate is the average rate at which one species branches to produce two groups that are reproductively isolated.” Pg 412

“In theory, speciation can occur rapidly whether it is sympatric, parapatric, or allopatric, and whether it is caused by genetic drift, natural selection, or sexual selection.” Pg 416

“in both cases (asexual reproduction and selfing plants) evolution has almost never gone in the opposite direction, probably because of the difficulty of re-evolving sexual reproduction and self-incompatibility once they are lost.” Pg 445

Luther Val Giddings, Kenneth Y. Kaneshiro, and Wyatt W. Anderson eds. Genetics, Speciation, and the Founder Principle (New York: Oxford University Press, 1989.)

“Once underway, rapid diversification may have been further promoted by self-incompatibility, frequent outcrossing, and hybridization between differentially adapted genotypes.” Pg 95

“Adaptive radiation in Hawaiian Bidens has occurred without the evolution of crossability barriers or intrinsic postzygotic isolating mechanisms.” Pg 101

Speciation depends on a substantive amount of available of available genetic variation in the founder population to respond to selection…” Pg 220

“In other words, speciation may not be phyletic evolution, except in the gradual acquisition of reproductive isolation.” Pg 226

“The population of an incipient species arises from a subpopulation of an existing species. “ Pg 352

 Karl J. Niklas.  The Evolutionary Biology of Plants Chicago: The University of Chicago Press, 1997.

“…there is no a priori reason to assume that survival and reproductive success are correlated.” Pg 20

“ The concept that individuals can be grouped into populations and that populations can be grouped into discrete biological units called species is a central tenet of biology.” Pg 63

“The issue is not whether species exist, or whether new species evolve from old ones. The existence of species as objectively recognizable entities was acknowledged long before Darwin demonstrated beyond doubt that evolution is the conversion of variation among individuals into differences among species. “ Pg 63

“In general, speciation is not directly observed but merely adduced after the fact. “ pg 63

“The tempo of speciation in the fossil record unquestionably agrees with that predicted by the theory of punctuated equilibrium.” Pg 108

Alec L. Panchen Classification, Evolution, and the Nature of Biology New York: Cambridge University Press, 1992.

“…[T]he theory of evolution states that the apparent relationships of organisms in a systematic classification are real relationships, because “relationship” in such classification is not a metaphor but is actually to be ascribed to community of descent.” Pg 3

“Whether or not a cladogram is taken to be a representation of phylogeny, it is primarily a representation of a hierarchy of characters.” Pg 56

“But classifications depend on characters possessed by the objects to be classified.” Pg 62

“In sexually reproducing organisms diversification in evolution is due to speciation.” Pg 152

“One major problem is the use of the concept of the “molecular clock”, the assumption inherent in phenetic uses of distance measures in phylogeny reconstruction (as distinct classification) that mutations in the DNA bases occur at a constant rate. “ Pg 208

E.O. Wiley. “Karl R. Popper, Systematics and Classification: A reply to Walter Bock and Other Evolutionary Taxonomists.” in Cladistic Theory and Methodology ed. Thomas Duncan and Tod F. Stuessy (New York: Van Nostrand Reinhold Company, 1985).

“The difficulties embodied in that part of evolutionary taxonomy which differs from phylogenetic systematics lead to a general lack of test ability of evolutionary classifications.” PG 46

W.H. Wagner Jr. (in the same work)

“Probably no phylogenetic cladogram, no matter how it is constructed, can be totally “proved” or “falsified.”” Pg 166

 Joseph H. Camin and Robert R. Sokal (in the same work)

“We have as yet no technique for dealing with cases of hybridization.” Pg 187

George Gaylord Simpson. Principles of Animal Taxonomy (New York: Columbia University Press, 1961.)

“In the larger pattern, however, no taxa (including species) can be strictly nonarbitrary as to exclusion. One must draw a completely arbitrary line, representing a point in time, across some steadily evolving lineage and say “ Here one taxon ends and another begins”. In principle that means that an individual animal could belong to one species one instant and to another species the next instant. That is seemingly absurd, but no more so than results of other available criteria for such necessary arbitrary divisions.” Pg 117-118

“…Speciation continues to be so crucial a point as frequently to be considered virtually synonymous with evolution.” Pg 149

­“As Mayr, Linsley, and Usinger, among others, have noted, any one supraspecific taxon up to about the categorical level of family tends to have fairly uniform adaptive facies, often recognizable to taxonomists at a glance.” Pg 200

David L. Hull “Cladistics Theory: Hypotheses That Blur and Grow” in Cladistics ed Thomas Duncan and Tod F. Stuessy. (New York: Columbia University Press, 1984.)

“…I do not think that claims made by cladists themselves can always be taken at face value.” Pg 16

Tod F. Stuessy and Jorge V. Crisci “Problems in the Determination of Evolutionary Directionality of Character-State Change for Phlogenetic Reconstruction.” (in the same work)

“Because we will never know a complete phylogeny (the closest we might come in in a group with an extensive fossil record), it is impossible to know if a criterion is providing accurate information about the true phylogeny or not.” Pg 75

Warren H. Wagner “Applications of the Concepts of Groundplan-Divergence.” (in the same work)

“It is possible, indeed, that most monophyly in the strictest sense can only be guessed at.” Pg 112

Joseph Felsenstein “The Statistical Approach to Inferring Evolutionary Trees and What It Tells Us About Parsimony and Compatibility” (in the same work)

“The difficulty we face is that we know too little to specify a realistic model of evolutionary change.” Pg188

Verne Grant Plant Speciation Columbia University Press; New York, 1981.

“Biological species, microspecies, and successional species, in distinction to the other two types, are natural units in the sense that they exist in nature and are not merely man-made categories.” Pg 79

“However, as we have noted earlier, the only species criterion that can be applied universally is practicality and convenience in identification and classification, and this criterion gives us a taxonomic unit which is basically artificial and often different from the natural units.” Pg 92

“Macrorecombinations are significant evolutionarily in showing that interspecific hybridization can engender not only intermediate forms but also products which are unlike either parent species.” Pg 100

 “Species differ, in other words, in their systems of genetic balance and in their adaptive gene combinations.” Pg 110

“Occasional or sporadic hybridization is normal in the plant kingdom when two or more related species come into contact.” Pg 197

“The syngameon is the most inclusive unit of interbreeding in a hybridizing species group.” Pg 234-235

“The phylogeny of many or most groups of higher plants which have been studied carefully in the field and laboratory is seen to be reticulate rather than exclusively dichotomous and branching. The model of the phylogenetic tree cannot be carried over from zoology into botany without misrepresenting the relationships in many instances. In all major groups of higher plants we have to deal with phylogenetic networks rather than phylogenetic trees.” Pg 481

“In short, we have to go well beyond mutation and selection in our  search for an adequate explanation of organic evolution.” Pg 487

Joel Cracraft “Speciation and its Ontology: The Empirical Consequences of Alternative Species Concepts for Understanding Patterns and Processes of Differentiation” in Speciation and Consequences ed Daniel Otte and John Endler Sinauer Associates Inc. Sunderland, MA, 1989.

“Species must be treated as discrete, real entities  because all theories require this: empirical theories cannot be about unreal, arbitrarily delimited entities and it would be biological nonsense to say “species are speciated” if they were not real things.” Pg 30

Gareth Nelson “Species and Taxa: Systematics and Evolution” in Speciation and Consequences ed Daniel Otte and John Endler Sinauer Associates Inc. Sunderland, MA, 1989. (in the same work)

“Evolution of taxa is not a phenomenon confined to the species level except in neodarwinian theory, which in this respect is simply false.” Pg 74

Douglas E. Gill “Fruiting Failure, Pollinator Inefficiency, and Speciation in Orchids” in Speciation and Consequences ed Daniel Otte and John Endler Sinauer Associates Inc. Sunderland, MA, 1989. (in the same work)

“The annoying, untestable, yet common answer often given these evolutionary speculations is that such mutations have not yet happened in any population of pink lady’s slippers. This historical constraint-accident hypothesis seems unlikely considering how abundant C. acuale is and how long (about 100 mya) the genus Cypripedium has been around. If such mutants have occurred, I cannot think of what barriers would prevent the immediate invasion and complete fixation of such mutations in the current populations of C. acaule. Similarly, I do not see why such mutants would not be instantly successful in any of the species of deceptive orchids.

These problems bring me to my fourth question: How did so many orchids evolve deceptive pollination systems when to do so involves reduced reproductive performance? If the plesiomorphic condition is considered to be nectar producing as Davni(1987) concludes, then how is the evolutionary loss of rewarding systems by natural selection explained? How did the 8000 deceptive species of orchids, many of which are apparently not part of a model-mimicry system, originate? At present, I have no idea.” Pg 476

John A. Endler  “Conceptual and Other Problems in Speciation” in Speciation and Consequences ed Daniel Otte and John Endler Sinauer Associates Inc. Sunderland, MA, 1989. 

Just as there are a variety of chisels made for different purposes, different species concepts are best for different purposes; and just as it is inadvisable to use a carving chisel to cut a mortise, problems arise when one species concept is used when it in inappropriate.”  Pg 625

Richard G. Harrison “Hybrid Zones Pattern and Process” in Hybrid Zones and the Evolutionary Process Oxford University Press, New York, 1993.

“Most Evolutionary change occurs slowly or sporadically; as a consequence, direct observation of change over time often yields limited information about the process of evolution.” Pg 1

“Hybrid zones are clearly a nuisance for those in search of a static species definition in which all individuals can be neatly catalogued as belonging to one species or another.” Pg 8

E. O. Wiley Phylogenetics John Wiley & Sons, New York, 1981.

“There is a natural phylogenetic tree of species existing as a historical by-product of evolution. Pgs 2-3

“Species comprise the highest level of taxonomic organization on which the processes of evolution work.” Pg 7

“The philosophical bases on which a scientist operates should  be clearly specified when those bases  affect the conclusion drawn.” Pg 20

“Whereas supraspecific taxa are collections of lineages, species are the lineages themselves. These  lineages  are placed in higher  groupings based on hypothesized past linkages. Thus, natural higher taxa are purely historical constructs whose sole existence. Depends on how accurately they document the historical unfolding of lineage splitting (speciation).”  Pg 26

“The formalism of taxonomy must give way to the perceived realities of evolution.” Pg 26

“While all valid special species concepts may be gathered under the larger concept of evolutionary species, there are several ways that species can gain their evolutionary independence. Thus it is not possible to relegate all special modes of speciation to a single higher concept.” Pg 38

“In a phyletically evolving lineage where characters are being replaced by their more apomorphic homologues, exactly where to draw the line between two species is entirely a matter of opinion.  How many of these species to recognize is also a matter of opinion.”   PG 40  (Note, Wiley is commenting on other people’s views, not explaining his own. He does not believe species are arbitrary)

“A natural taxon is a taxon that exists in nature independent  of man’s ability to perceive it.” Pg 72

“A monophyletic group is a group of species that includes an ancestral species (known or hypothesized) and all of its descendants.” Pg 76

“The most basic kind of phylogenetic tree portraying the relationships between species and supraspecific taxa, and the one with the most inherent information is a tree of species. In such a tree, the lines portray evolutionary species and the branches are graphic representations of speciation events. All specialized trees are reducible to such a diagram.” Pg 93-94

“Species may stand as ancestral to other species or to higher taxa. But, higher taxa cannot be ancestral to other higher taxa because higher taxa are not units of evolution, but historical units composed of separately evolving species.” Pg 107-108.

“For the purpose of working on a limited problem, the investigator assumes the most highly corroborated higher level phylogeny to be true. Such an assumption is permissible because the higher level phylogeny is, itself, open to testing at a higher level of universality than the problem at hand.” Pg 112

Commenting on error analysis

“There are no known models of phylogenies with which the phylogenetic systematist can empirically calculate the chances for either types of error.” Pg 114

‘A character is a feature of an organism which is the product  of an ontogenetic or cytogenetic sequence of previously existing features, or a feature of a previously existing parental organism(s).  Such features arise in evolution by modification of a previously existing ontogenetic or cytogenetic or molecular sequence.” Pg 116

“If phylogeneicists had some absolute criterion for identifying synapomorphous homologies, phylogenetics analyses would be error free.  Phylogeneticists, like all other scientists, do not have an insight to such absolute truth and can only present their hypotheses as best estimates of the truth.” Pg 130

“Of course, the absolute truth about any hypothesis of homology will never be demonstrated because the one true phylogeny for any given set of organisms will never be known.” Pg 138

“Classifications of individuals and historical groups differ from classifications of natural classes in that classifications of individuals and historical groups are inherently hierarchal. The hierarchy may be explained in one of two ways. First, it might have been produced by the logical mind of a creator. Linnaeus and Agassiz perceived the basis of the hierarchy in this manner. Second, it might have been produced by the fact that all organisms (or languages or continents) are historically connected in the genealogical sense. Lamarck, Buffon, Darwin and other evolutionists perceived the basis of the hierarchy in this manner. The former basis is an adequate basis for searching for order among living organisms (surely this must be correct or nonevolutionists would not have done such a good job classifying). However, it is an inadequate philosophy because it stops short of attempted explanations of the hierarchy. Everything is ascribed to the hand of God. The latter (evolutionist) perception is also an adequate basis for searching for order. It also provides an adequate basis for attempting natural explanations of the origins of the hierarchy.” Pg 196-197

“The vast majority of our classifications are convenience classifications. They are a by-product of our desire to bring order into language.” Pg 197

“The kind of quantitative characters an investigator will select depend on the purpose of the study.” Pg 340

Daniel R. Brooks and Deborah H. McLennan Phylogeny, Ecology and Behavior University of Chicago Press, Chicago, 1991.

“Those traits occurring only within the study group are special similarities. The members of the study group are then clustered according to their special shared traits. If there are conflicting groupings, it means that some traits assumed to be evolutionary homologies on the basis of nonphylogenetic criteria are actually homoplasies. Because all evolutionary homologies covary and homoplasies do not covary, the pattern of relationships supported by the largest subset of special similarities is adopted as the working hypothesis of phylogenetic relationships. As more and more traits are sampled there will be progressively more support for a single phylogenetic pattern. Traits that are inconsistent with this pattern are interpreted, post hoc, as homoplasies.” Pg 14

“Microevolution and macroevolution are thus considered to be parts of a more inclusive whole represented by the hierarchical nature of biological systems. Since macroevolution is neither autonomous from nor reducible to microevolution, robust evolutionary explanations require data from both sources.” Pg 16

“Hence. The approach advocated by Hennig is not circular because homologies, which indicate phylogenetic relationships are determined without a priori reference to a phylogeny, while homoplasies, which are inconsistent with phylogeny, are determined by reference to a phylogeny.” Pg 25-26

“Since phylogenetic trees are hypotheses and not “facts”, they are dependent upon both the quality and quantity of  data that support them.” Pg 31

Never assume convergent or parallel evolution; always assume homology in the absence of contrary evidence. The principle is a powerful one. Without it we could assert that all characteristics “probably” arose multiple times by convergent evolution.pg 35

Does the method assume or rely on any particular evolutionary mechanism? No. it assumes only that evolution has occurred. In fact, the utility of phylogenetic systematics in evolutionary biology stems from its independence of any particular evolutionary mechanism.” Pg 64

“Speciation has always been a central process in evolutionary theory. It follows, then, that if speciation is a “real” process, species must be “real” in some sense relevant to evolution.” Pg 73

“Biological species are real, but not in the same sense that “hydrogen” is real. A molecule of hydrogen found anywhere and formed at any time in the universe would be a member of the class hydrogen. By contrast, an organism that looks like a tiger on this planet would not be part of the same species as an organism that looks like a tiger on another planet unless the two organisms shared a common ancestor. “ pg 74

“It should be clear by now that no one process can be assigned the dominant role in evolution; every clade is a unique combination of historical and environmental influences.” Pg 185

Mary Pickard Winsor “The Lessons of History” in Models in Phylogeny Reconstruction,  eds. Robert W. Scotland, Darrell J. Siebert and David M. Williams Clarendon Press, Oxford, 1994.

“We all have our biases. The wonder is that any of us do come close to the truth about the past instead of just constructing a plausible story.” Pg 2

Olivier Rieppel “Species and History” (in the same work)

“The method proposed to recover ‘historical structure’ is that of phylogenetics systematics.” Pg 33

“The ‘reality’ of species has been rooted in the ‘fact’ (which, in fact, is an assumption) that they are a result of or take part in the process of evolution.” Pg 34

“A ‘species’ or ‘Canis familiaris’, is not a thing, nor a particular, but a notion for perceived relations among things, an expression of relative invariance (of any kind of relation) within a multiplicity of appearances.” Pg 37

“Although a central tenet of modern biology, evolutionary theory is not a ‘fact’, but a causal explanation for observed regularity of character distribution.” Pg 38

“So why not cut the Gordian knot by admitting that species do not, in fact cannot exist in an evolving world, and that species are, in fact what they have always been: a conceptual tool in the attempt to master biological diversity.” Pg 46

“Species do not evolve but evolution takes place within the species.” Pg 46

Colin Patterson “Null or minimal models” (in the same work)

“Apart from negative and facetious answers, about the only response I have ever had [ to the question, what about evolution is true] is ‘evolution generates hierarchy’. In 1981, I knew of no sensible answer to the question, but in the ensuing decade I came to believe that there were two things I knew about evolution.  First, that transitions  are more frequently fixed than transversions; and second, that, at the level of DNA, the great majority of substitutions  take place despite natural selection rather than because of it.” Pg 175

David Penny, Peter J. Lockhart, Michael A. Steel, And Michael D. Hendy “The role of models in reconstructing evolutionary trees. ” (in the same work)

“We would stress that an evolutionary model is NOT just the mechanism of character change; it includes the assumption of searching for a tree as the underlying relationship among the taxa.” Pg 212

 Mark Ridley Evolution and Classification  Longman Group Limited, London, 1986.

“So taxonomists are faced with a choice. They have to choose some characters rather than others. They might, of course, pick characters arbitrarily and define arbitrary groups, but in practice they do not. They generally try to choose particular kinds of characters; and their choice is dictated by taxonomic principle…Taxonomists have been forced to develop a philosophy, in addition to the practical task of defining groups by the fact that different characters disagree.” Pg 2

“These characters are merely crude description. Characters can also be defined theoretically. They can be divided into evolutionarily stable characters which (we infer) do not change during evolution, and evolutionarily labile ones, which change more often. Or they can be divided into evolutionarily ‘ancestral’ characters and evolutionarily derived ones, which are earlier and later evolutionary states of the same character; fins and limbs are an example.” Pg 2-3

“Evolution has produced the natural groups of life; classification should seek to be natural rather than artificial; classification should therefore represent evolution. Evolution results in natural groups because all evolutionary change takes place in the same phylogenetic tree: all changes in all characters must have taken place within the same pattern of lineages.” Pg 19

“Evolutionary classifications are always subject to improvement.” Pg 27

“All the genes of a set of species with typical Mendelian inheritance have descended through the same phylogenetic hierarchy: the phylogeny of cytochrome genes in vertebrates is the same as the phylogeny of haemoglobins. That is why phylogenetic classification is unambiguous. If, however, the different genes of a ‘species’ had experienced different phylogenetic histories, and the species themselves had experienced mixed ancestries, Hennig’s arguments would break down.”  Pg49

“Evolution may not be maximally parsimonious. Indeed, in a trivial sense, we know it is not: ‘probably the most parsimonious outcome of evolution would be for it not to occur at all.’ (Felsenstein, 1983a p 321) But even given that evolution has taken place, it may still not in fact been as parsimonious as it could.” Pg 82

“Before we can call something a test of evolution, we must specify what the alternative is. The most obvious alternative would be the biblical book of Genesis. But if taken literally, Genesis runs into trouble with some simple facts of geology. If I was asked why I do not accept Genesis, I should immediately seize on the geological evidence of the age of the Earth.” Pg 117

“This being so, the mere fact that biological classification is hierarchical does not prove that evolution has taken place.”  Pg 117

“All that is needed to prove evolution is observed microevolution added to the philosophical doctrine of uniformitarianism, which (in the form that is needed here) underlies all science.”  Pg 119

“Cladism needs evolution in its techniques, although not actually to operate them in the day-to-day practical sense. It needs evolution in its philosophy. The theory of evolution is necessary–not just desirable or decorative–in the justification of cladism.” Pg 162

N.R. Scott-Ram Transformed Cladistics, Taxonomy and EvolutionCambridge University Press, Cambridge, 1990.

“It is therefore impossible to have an ideal and absolute classification for any particular set of objects. It is misleading to talk of the one classification.”  Pg 115

“ However, phylogenetic cladists who believe that evolution is divergent will not attempt to discover instances of convergence, and any error encountered in the ‘fit’ of the tree pattern to their model will be ignored. A fixed picture of evolution will be presented and all counter instances will be explained away as faults in the method, when really the model is at fault.” Pg 118

“All  phylogenetic cladists adopt the basic premise that life has evolved.” Pg 179

Willi Hennig Phylogenetic Systematics, trs. D. Dwight Davis and Rainer Zangerl, University of Illinois Press, Chicago, 1979.

“The assumption that the species category determines the systematic work with relation to a very distinct group of relationships, and thus to a determined scientific system, is false.” Pg 8-9

“ If individual variability exceeds a certain degree the aberrant individuals are often given species names as “varieties” or “abberations.” The decision as to what degree of  deviation warrants giving the aberrant individuals or groups of similar aberrant individuals the rank of a named variety or aberration is completely arbitrary.” Pg 37

“It might seem that the difficulties surrounding the species concept, or the impossibility of determining the species limits with certainty in some cases , would destroy or at least considerably disturb the intent of phylogenetic systematics to subsume in groups (taxa) of higher rank those species that arose by splitting up of a common stem species. This, however, is not the case.

“For the taxonomy of the higher categories it is without essential importance that the process of speciation is usually a relatively long, drawn out process, so that a cross section through the species stock at a particular time–the present, for example–shows several species in different phases of their cleavage. The subsuming of species on group categories of higher order according to the degree of their phylogenetic relationship depends on a process of measuring–measuring the time since the fundamental event of speciation, i.e., the species cleavage that led to the origin of the higher taxon.  Since this involves time spans of geological magnitude, which are longer the higher the rank of the taxon, the time required for a phylogenetically significant process of speciation is negligible.  Systematists can neglect it without being charged with superficiality, and without fear of failing in its aim.” Pgs 52-54

“Evolution does not become phylogeny through a single process of species splitting. Phylogenesis is the origin of groups of species from a stem species and its descendants by progressive splitting, resulting in a later evolutionary condition than that of the original stem species.” Pg 199

“A much better point of departure is to recognize that evolution is a fact and that its course and the conformities to law that control it must be investigated.” Pg 234

Oliver Mayo Natural Selection and its Constraints London: Academic Press Inc. Ltd, 1983.

“In essence, an evolutionary explanation is a historical interpretation, and so may not yield predictions which can be tested now.” Pg 1

“Natural selection is a very general term describing a vast range of possible mechanisms.” Pg 3

“Fitness, in the sense of ultimate reproductive success, is evidently  only measurable after the fact, i.e. over particular known lineages for defined times.” Pg 37

“ Thus, the problem is essentially that of determining the relative proportions of actual changes which have occurred as the result of random fixation of neutral (or perhaps very slightly deleterious) mutants or as the result of natural selection of advantageous mutants.” Pg 45-46

“Given the long time over which evolution has occurred, the extinction of most taxa that have ever existed, and the short life span of humans this would seem to suggest that no evolutionary hypothesis was subject to experimental verification. “ pg 104

“The major constraint on natural selection as an agent of change is natural selection as a stabilizing force.” Pg 104

Oliver Mayo Natural Selection and its Constraints London: Academic Press Inc. Ltd, 1983.

“In essence, an evolutionary explanation is a historical interpretation, and so may not yield predictions which can be tested now.” Pg 1

“Natural selection is a very general term describing a vast range of possible mechanisms.” Pg 3

“Fitness, in the sense of ultimate reproductive success, is evidently  only measurable after the fact, i.e. over particular known lineages for defined times.” Pg 37

“ Thus, the problem is essentially that of determining the relative proportions of actual changes which have occurred as the result of random fixation of neutral (or perhaps very slightly deleterious) mutants or as the result of natural selection of advantageous mutants.” Pg 45-46

“Given the long time over which evolution has occurred, the extinction of most taxa that have ever existed, and the short life span of humans this would seem to suggest that no evolutionary hypothesis was subject to experimental verification. “ pg 104

“The major constraint on natural selection as an agent of change is natural selection as a stabilizing force.” Pg 104

George C. Williams Natural Selection: Domains, Levels and Challenges New York: Oxford University Press, 1992.

In the usual textbook accounts, and in most applications by professional biologists, natural selection operates by the reproductive successes and failures of organisms in populations. Shifting gene frequencies keep the record of success and failure because greater reproductive success for any individual means greater prevalence of its genes in the future. There is nothing in this process that can anticipate future needs or foster adaptations.” Pg 5-6

“The neck skeletons of  giraffe, man, and mouse are all marvels of mechanical engineering for the different ways of life of these divergent mammals. Yet all have seven vertebrae in this region, a functionally inexplicable uniformity. The only acceptable explanation is historical, descent from a common ancestor with seven cervical vertebrae.” Pg 7

“Information can proliferate and be edited by natural selection only if the selection affects the information at a greater rate than competing processes such as mutation and drift.” Pg 13

“Reproductive success is measured by the magnitude of the interactor’s lifetime total of genes put back into the gene pool, relative to the performance of others in the population.” Pg 16

“A gene is that which reliably survives the process of meiosis intact.” Pg 18

“The microevolutionary process that adequately describes evolution in a population is an utterly inadequate account of the evolution of Earth’s biota.” Pg31

“Design of organs, developmental programs etc. are legacies from the past and natural selection can affect them in only two ways. It can adjust the numbers of mutually exclusive designs until they reach frequency-dependent equilibria, often  with only one design that excludes alternatives. It can also optimize that design’s parameters so as to maximize the fitness attainable with that design under current conditions.” Pg 56

“My postulated choice mechanism would always lead a female to choose a male with statistically extreme ornamentation or weaponry or social status. The fitness benefit would not be the acquisition of superior paternal genes for offspring, but an increased assurance of providing them with enough paternal gametes.” Pg110

“The species is thus a key taxonomic concept but that is all it is. It is not fitting, in my opinion, to endow the species concept with theoretical significance beyond that of a widely recognizable level in the taxonomic hierarchy.” Pg 119

“I find it very puzzling that no shift in selection pressures in the last 100 million years would have produced any noteworthy change in a structure as complex and informative as a fish skeleton, which ought to reflect even very subtle changes in locomotor or trophic adaptations.” Pg 132

“ How can these observations of rapid evolution be reconciled with the stasis often (usually?) found in the fossil record for periods of millions or tens of millions of years? In Chapter 8, I took the traditional course of blaming the imperfections of the fossil record. But what kind of imperfection must be postulated to explain the appearance of widespread stasis in a biota in which most populations are evolving rapidly? I suggest that the record simply fails to provide enough short-term detail on phylogenetic changes at any one time, such as those in progress in the complexes of species referred to as leopard frogs or threespine sticklebacks.” Pg 132

“The data makes no evolutionary sense. Why has there not been a major adaptive radiation of temperature set points? Would there not be a great energy saving for a snow bunting or arctic fox that kept its body at 28(Celsius) rather than 38? Would it not be advantageous for a gazelle or baboon fleeing from hyenas over a sun-baked Arabian plain to operate at 48, and likewise for the hyenas? Why should there be such enormous diversity in a long list of character in both birds and mammals (think of whales, anteaters, bats, penguins hummingbirds, moas) but so little in this one character?” pg 136-137

“In my opinion, the problem (Haldane’s dilemma) has never been solved, by Wallace or anyone else.” Pg 143

John Tyler Bonner The Evolution of Complexity by Means of Natural Selection Princeton: Princeton University Press, 1988.

“In modern terms, natural selection operates on genetic variation; that is to say, those individuals with certain favorable genes and gene combinations will not only survive, but will be relatively more successful in producing offspring, and the result will be that the genes they possess will survive by being passed on to descendants.”

“If we pursue the plant line, we see a major division between the photosynthetic plants and the nonphotosynthetic plants, the fungi. Again, the early fossil record is inadequate, or almost nonexistent, and we must reconstruct from what we know of modern forms.” Pg 9

“The standard and correct answer one would receive from any biologist today is that the sweep of evolution is the result of natural selection. This is certainly the prime mover in all evolution.”  Pg 10

“Again, Darwin was fully aware of the key role played by competition in driving natural selection. The successful individual animals that exploited food were the ones that reproduced; and the plant that caught most of the sun for photosynthesis prospered, while those forced into the shade of a larger plant waned and produced few or no seeds.  One of the prime moving forces behind natural selection is competition.” Pg 20

“Part of the difficulty is what a paleontologist considers a species may be a quite different thing from the species of a biologist. Even the biological definition is an enormous problem and may well be different things in different groups of animals and plants. “ Pg 50-51

“Unfortunately, it is difficult to find any one set of criteria (for species) that is satisfactory for different groups of organisms, and sometimes it is equally difficult to find a perfect set for a small restricted group.” Pg 51

M. Cook Coefficients of Natural Selection London: Hutchinson University Library, 1971.

“Selection may then be defined as ‘all systematic modes of change in gene frequency which do not involve physical transformation of the hereditary material (mutation) or introduction from without (immigration)’.” Pg 19

“When we speak of natural selection we imply that those who survive have a greater fitness than those who do not.” Pg 19

“Except where specifically qualified we shall define natural selection in a more limited manner throughout this book, as the action of any agency which causes a relative change in the number of progeny from two kinds of organisms which survive to reproductive age.” Pg 19

“It has been emphasized that the standard treatment of selection tells us nothing about the density or the rate of change in numbers of a population. Most of the time the study of selection cannot do so.” Pg 162

 GEORGE C. WILLIAMS  Adaptation and Natural Selection Princeton: Princeton University Press, 1972.

“One is that a biologist can make any evolutionary speculation seem scientifically acceptable merely by adorning his arguments with the forms and symbols of the theory of natural selection.” Pg 21 (discussing problems with the lack of a unified theory of adaptation.)

“Another tendency that survives, despite its lack of theoretical justification, is a belief in a deterministic succession of evolutionary stages.” Pg 21

“The natural selection of phenotypes cannot in itself produce cumulative change, because phenotypes are extremely temporary manifestations. They are the result of an interaction between geneotype and environment that produces what we recognize as an individual.” Pg23

“Natural selection commonly produces fitness in the vernacular sense.  We ordinarily expect it to favor mechanisms leading to an increase in health and comfort and a decrease in danger to life and limb but the theoretically important kind of fitness is that which promotes ultimate  reproductive survival.” Pg26

“We can interpret evolution since the Cambrian as a history of substitutions and qualitative changes in the germ plasm, not an increase in its total content.” Pg 42

“I regard it as unfortunate that the theory of natural selection was first developed as an explanation for evolutionary change. It is much more important as an explanation for the maintenance of adaptation.” Pg 54

“The elaborateness and precision of morphogenetic machinery requires a certain burden of genetic information.” Pg 84

“It should be clear that, in general, the fossil record can be a direct source of information on organic evolution only when changes in single populations can be followed through a continuous sequence of strata.” Pg 98

“So evolution takes place, not so much because of natural selection, but to a large degree in spite of it.” Pg 139

“I have no reason to doubt that introgressive hybridization may be an important evolutionary factor in some groups.” Pg 145

“An individual is fit if its adaptations are such as to make it likely to contribute a more than average number of genes to future generations.” Pg 158

Peter R. Grant  Ecology and Evolution of Darwin’s Finches Princeton: Princeton University Press, 1986.

“Faced with uncertainty, an evolutionary biologist behaves somewhat like a detective called in to solve a crime. He combines all available clues about past events, including those provided by fossils, with a study of current processes, postulates the most likely courses of past events given this information,  then tests the postulates with new data whenever possible to see which has the most explanatory power.” pg 11