There have been several Skeptoid posts over the last month that touched base with evolution and evolutionary theory. Several time the terms “Macroevolution” and “Microevolution” have been used by commentators articulating what I would term a denial of evolutionary science. These terms were used so much that I though it reasonable for focused review of what these arguments mean, and who uses it.
Microevolution Simplified: ” Microevolution is a change in gene frequency within a population. Evolution at this scale can be observed over short periods of time — for example, between one generation and the next, the frequency of a gene for pesticide resistance in a population of crop pests increases. Such a change might come about because natural selection favored the gene, because the population received new immigrants carrying the gene, because some nonresistant genes mutated to the resistant version, or because of random genetic drift from one generation to the next.”
Macroevolution Simplified: Refers to any evolutionary change at or above the level of species. It means at least the splitting of a species into two (speciation, or cladogenesis, from the Greek meaning “the origin of a branch”) or the change of a species over time into another Any changes that occur at higher levels, such as the evolution of new families, phyla or genera, are also therefore macroevolution, but the term is not restricted to those higher levels. It often also means long-term trends or biases in evolution of higher taxonomic levels.
Microevolution happens on a small scale (within a single population), while macroevolution happens on a scale that transcends the boundaries of a single species. Despite their differences, evolution at both of these levels relies on the same, established mechanisms of evolutionary change.
A common argument/tactic for protesting the scientific veracity of evolution revolves around challenging one or both of these terms.
First of all they are terms not scientific processes or specific descriptions of processes. They are used by evolutionary biologists but they do not specifically describe any specific genetic or selective process. They are merely categories. Arguments using these terms often boil down to “A happens but B does not therefore evolution is wrong”.
Words are not the master of science; science is, or should be, the master of its words. But we can inquire how scientists use their words, and whether they use them consistently. And having done that, we can inquire whether others who are not scientists read too much into them, or use them in a totally different way.
Here is good example of a Macroevolution argument from a prior post of mine.
“anonymous“-“Macro” refers to large changes in a population resulting in speciation, in which there are two kinds. One is caused by new genetic information in which a new species arises, and is the evolution that is disputed by creationists. The other form of macro evolution is speciation due to a loss of genetic data. A good example would be plant species that mutates, altering it’s pollination time, preventing it from naturally pollinating within the general population. Micro evolution would be simple changes within a population that do not occur from new information, but simple mixing of information. Examples are differences between parents and their offspring, as well as different characteristics between ethnic groups of people or breeds of animals.
As far as to what I am considering to be new information, I’m asking how or where it’s demonstrated that entirely new genes are developed. Point mutations are shown to alter genes that already exist. Are there examples of new genes occuring? There should be examples of novel genes being developed, that’s what I’m looking for. Point mutations within a gene is still not adding new information, which I think is what you are pointing to, though Argent47 may have some more specific info that may say otherwise according to his post. I hope he can give give me some more detailed info or point me to where I can find the published research.”
Let’s examine this argument in detail. What are the premises of the argument?
Evolutionary change requires informational increases in the genomes of organisms. Also that mutations are the only ways that this can happen (if other processes accounted for an increase, it would not be an argument against evolution). Plus, that mutations themselves cannot produce informational increase.
The first premise is not strictly true: evolution is defined as the adaptation of a population of organisms to its natural environment, and this does not necessarily require the information of the genome to increase. It can as easily decrease.
But, do point mutations cause informational increases in the genomes of organisms, like creationists say they don’t? 100% correct, no, they don’t.
Like many non-scientific thought processes this one revolves around a central speck of truth with false extrapolations caused by poor understanding of the discipline. Point mutations don’t cause an increase in the individual genome’s informational content, but rather in the population’s gene pool as a whole. Changing one base pair in a genome does not change the informational content at all. The removal of one allele (gene variation) and replaced it with another. This ignores the fact that individuals do not evolve, populations do. A point mutation becomes the bringer of new genetic variation, which then can be pruned back with natural selection into a different population of organisms. Gene duplication is another mechanism that can increase of information in the gene pool and the genomes of individual organisms.
Gene duplication occurs when one gene is copied incorrectly and the organism gets two copies of the same gene in its genome. How does this relate to information increase? Point mutations changed one gene into an allele of itself. What if you had a point mutation in one of the copies, and the other remained the same? You would end up with the original gene and a variant of that gene, in the same organism. This results in a completely new gene. Given enough mutation voila evolution of a new gene. Transforming, biochemical pathways and transcription factors resulting in new expressed traits and subsequent selection.
Where are the examples? Most of these processes occurred in early earth history.
Life on Earth is at least 3.4 billion years old. Multicellular creatures first appear in the fossil record about 540 million years ago. That means that most of the history of life on Earth, about 3 billion years, was nothing but single-celled creatures. That is a very long time in which to evolve biochemical pathways and cellular complexity – more that 5 times as long as it took to get from a single cell to a person. Cells, proteins, RNA, organelles, and biochemical pathways do not fossilize. They are scantly preserved at all. We are therefore limited in our ability to reconstruct the evolutionary history of billions of years of evolution on this scale. Scientists only have a few methods available from which to infer the evolutionary history of cell structures and biochemical pathways. The main method is to look for patterns in living organisms. By analyzing thousands of species, they can partially reconstruct the evolutionary tree.
Perhaps the best method available is genetic analysis. Genes are a sort of fossil – they do record to some degree their evolutionary past. We can see when genes duplicated and then evolved to take on new functions. We can sometimes see inactivated genes, truly fossil genes, and infer past function from them.
That is why this part of evolutionary theory has been the focus of creationist arguments. New genetic information is a complicated, slow, time intensive process. It occurred primarily in early earth history, and has only limited examples now. Not zero examples just few examples.
There are current examples. Here are two.
- Further examples of evolution by gene duplication revealed through DNA sequence comparisons.
- The evolution of trichromatic color vision by opsin gene duplication in New World and Old World primates
The next step in the no Macroevolution argument usually refers to Chromosomal issues.
Evolution can explain diversity in a limited number of created kinds which can interbreed (which they call “microevolution”) while the formation of new “kinds” (which they call “macroevolution“) is impossible. This is acceptance of “microevolution” only within a “kind”.
Essentially they are describing the same process. Although evolution beyond the species level results in beginning and ending generations which could not interbreed. Chromosomal changes can be explained by intermediate stages. A single chromosome divides in generational stages, or multiple chromosomes fuse. Examples of this are found in the human and comparative genetics of apes. Again not impossible, just difficult for lay persons to understand.
The last ditch denial argument is usually to point to a no-true Scotsman logical fallacy. A simple rendition of the fallacy would be:
Person A: “No Scotsman puts sugar on his porridge.”
Person B: “I am Scottish, and I put sugar on my porridge.”
Person A: “Then you are not a true Scotsman.”
Any example of “Macroevolution” is broken down as not “true evolution”. This is based upon the relatively arbitrary demarcation of what the term means. They redefine macroevolution as something that cannot be attained. Any observed evolutionary change as “just microevolution”.
DanH: “All these examples of microevolution are fascinating. My particular favorite is the abundance of the Kermode black bear (called the Spirit Bear due its white color by the natives) in British Columbia.
What I am waiting for is evidence of marcoevolution, specifically how different chromosomal species occurred. All the previous examples involve evolution within a species”
Even allowing for the misspelling clearly this a psudoscientific demarcation of a no true Scotsman fallacy. Only different chromosomal species qualify for “Macroevolution”. That is not the definiton of Macroevolution. It is however a no true Scotsman fallacy.
In truth evolution within species is evolution. Just not the only kind. It is a trick that sounds good to lay persons but it false. For example bacterial plasmids will transmit antibiotic resistance to other bacteria. Sometimes across completely different species resulting in a new organism with a distinctly different genome. At one time there was no nylon on earth yet now we have nylon eating bacteria. Evolution. Only rapidly reproducing species produce current examples of mutation derived evolution. The more time involved the stronger the evidence. Most humans 7500 years ago did not have the ability to digest bovine milk. Now it is a common trait. Since genetics is a young science and evolutionary theory dictates significant time is necessary for mutation derived evolution, it is likely that examples are scarce. It does not refute the theory as a whole.
These arguments are a nonscientific use of scientific terms in an attempt to poke a hole in the total theory of evolution. This is a purposeful attack where the reproducible evidence is the weakest, and the science is the hardest for a lay person to understand. These arguments use scientific terms incorrectly to arbitrarily demarcate evolution into a more manageable target. This is because negating the whole of evolutionary evidence is impossible.
To disprove evolution you would have to disprove everything we know about.
- The Fossil Record
- Comparative Anatomy
- Convergent Evolution
- Divergent Evolution
- Comparative Embryology
- Comparative Molecular Biology on the anatomical level
A no true Scotsman logical fallacy and poor understanding of genetics just doesn’t cut the convergent lines of evidence from these scientific disciplines. In my opinion it is fruitless waste of time to try to argue these points with proponets. These arguments are predicated on the maxim; say it a lot, say it with conviction, and people will believe.
Belief is not science it is just belief.
Griffiths, William M.; Miller, Jeffrey H.; Suzuki, David T.; Lewontin, Richard C.; Gelbart, eds. (2000). An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman.
About Stephen PropatierStephen Propatier is a board certified acute care nurse practitioner specializing in spine and sports medicine. He is a member of the Society for Science Based Medicine.
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What is the difference between Microevolution and Macroevolution?
Macroevolution is generally used to refer to any evolution above the level of species.
However, there are significant failings to using species as the threshold for ‘macroevolution’:
First, there are weaknesses to using species as the demarcation between microevolution and macroevolution:
- It makes the meaning of macroevolution subjective and inconsistent, even arbitrary.
- It is anachronistic – it overrates the significance of species and speciation.
- It makes the term macroevolution of little, if any, explanatory value – we might as well just use supra-species.
Second, it is inappropriate to have such a low threshold for macroevolution, because the same word is also used for evolution on the largest scale; and there are substantial pitfalls to this breadth of meaning:
- It does not deal consistently with mutations – it is used too loosely – for minor evolution that does not involve mutations, right up to the emergence of new body plans.
- Hence, it obfuscates and militates against clear thinking / understanding of the processes that are taking place in any instance of evolution.
- And it misleads: because this usage includes evolution that is due solely to the segregation of existing genes which definitely occurs, and to evolution that would require new genes, it can give the false impression that instances/examples of the former substantiate the latter.
So here I suggest that the usual usage of ‘macroevolution’ is flawed and that it would be better to use this term to describe evolution that requires meaningful or constructive new genetic material – which is how I use it in this website, and in Evolution under the microscope.
I conclude with comments about whether macroevolution is just accumulated microevolution.
Although the usage of ‘microevolution’ and ‘macroevolution’ are not entirely consistent, in terms of how they are most commonly used the difference between them is straightforward:
For a useful review see 'Macroevolution: Its Definition, Philosophy and History’ by John Wilkins, talkorigins.org /faqs/macroevolution.html
- Microevolution is evolutionary change within a species.
- Macroevolution is evolutionary change above the level of species,
i.e. when a species changes sufficiently to be called another species (called anagenesis), or one species diversifies into two (or more) which is called speciation.
A well-known example of this is the spread of industrial melanism within the peppered moth during the 19th century (and the reversal of this change since the mid 20th century).
Another would be the changes in beak sizes of some species of Galapagos finches, apparently in response to environmental pressure.
An uncontentious example of this would be the diversification of an ancestral finch (from the S. American mainland) as it dispersed among the Galapagos Islands and adapted to various habitats to produce the present range of Galapagos finches.
A more controversial example would be the presumed evolution of birds from dinosaurs.
Unfortunately, behind this clear façade lies some unclear thinking and wayward reasoning.Failings of linking ‘macroevolution’ to speciation
It makes the meaning of macroevolution subjective and inconsistent, even arbitrary
A notable example of this is that lions and tigers – readily accepted as different species – in captivity may hybridize – to produce ligers and tigons – which can be fertile..
The definition of species is imprecise or even variable. Although it is commonly said that a species is based on the ability to interbreed, i.e. that a species includes all individuals capable of interbreeding (and producing fertile offspring), in practice most defined species are characterised on the basis of being morphologically distinct i.e. even if they can interbreed with other defined species, especially if the morphologically different populations are also separated geographically (perhaps so that normally they do not interbreed, even though they could). This means that the number of defined species is far higher than it would be if all individuals capable of interbreeding were considered to be one species.
A notable example of this is that lions and tigers – readily accepted as different species – in captivity may hybridize – to produce ligers and tigons – which can be fertile..
Significant in this context is that the segregation into and definitions of many species are relative and based to a large extent on the subjective view of the classifier, and often take into account the number and variety of the (group(s) of) individuals to be classified rather than any fundamental basis or other objective criteria. (Note that I’m not criticising this approach, it probably makes taxonomic sense; but this practice does mean that the threshold for macroevolution is relative rather than absolute.)
So, given the various – and varying – criteria for defining species, if the definition of macroevolution is based on the formation of species (whether by speciation or anagenesis) then what this term means will vary depending on the context; i.e. what (e.g. degree of morphological difference) would be considered to constitute macroevolution in some contexts would not in others.
For further information and discussion about the definition of 'species' see Wikipedia articles ‘Species’ and ‘Species problem’.
Surely it would be preferable for ‘macroevolution’ to have a more significant meaning than this?
It is anachronistic
Indeed, defining macroevolution in terms of speciation is anachronistic. It stems from the classical idea of the ‘fixity of species’ which arose from Plato’s idealistic view of the world  and persisted up to the scientific revolution. Buffon (in the 18th century) illustrated this way of thinking when he said that
Comte de Buffon (1707-1788)
… if it were proved … that a single species was ever produced by the degeneration of another ... no bounds could be fixed on the power of Nature.
In other words, so strong had been the hold of the doctrine of the fixity of species in the minds of the natural philosophers that they had perceived each species being demarcated by a ‘species barrier’; and when they identified a significant change, even if small, in the morphology of a species, by breaking through this perceived barrier they felt that this meant there would be no limit to the degree of change that might occur.
And Darwin followed that, believing that the changes occurring through domestic breeding, even though it was known at the time that they were limited, could be extrapolated without limit in nature.
But Buffon, Darwin and their contemporaries were completely unaware of the innate genetic diversity of species which enables substantial changes in morphology to be achieved simply by shuffling and selecting subsets of the available genes. And – crucially – that there is a limit to the morphological changes that can be achieved in this way, and that to go further requires new genes.
Richard Dawkins recognises this:
If anything, selective breeders experience difficulty after a number of generations of successful selective breeding. This is because after some generations of selective breeding the available genetic variation runs out, and we have to wait for new mutations. 
So we need to take on board our modern knowledge and understanding of genetics: that not only significant morphological change but also speciation (as it is generally used) can arise solely through segregating and selecting different subsets of genes from an initial gene pool (e.g. the Galapagos finches); i.e. that the perceived ‘species barrier’ is not as significant as the early biologists thought; in fact there is no barrier at all.
The point is this: now that we know that the old idea of the fixity of species was wrong – that there is no notional species barrier, and no particular significance attaches to speciation – we should not fall into the same trap as Buffon and Darwin and think that because a species can change and/or divide into two or more different species that this demonstrates that any amount of evolutionary change is possible.
Unfortunately it suits supporters of evolution to keep the idea that speciation is a big deal – as if it did prove the case for evolution as a whole. And using ‘macroevolution’ for any evolution above the species level suits their purpose.
It makes the term 'macroevolution' of little, if any, explanatory value
Stephen J. Gould (1941-2002)
In his essay on Macroevolution in the Encyclopedia of Evolution Stephen Jay Gould tried to bring some clarity to the discussion by noting that, quite apart from relating macroevolution to any particular taxonomic level (such as species), the term can be used in two substantially different ways: 
- Simply as a descriptive term, i.e. without inference about causes or mechanisms.
For Gould that meant any evolution above the level of species (he excluded anagenesis), but the principle could apply to higher taxonomic levels.
- In a causal sense, i.e. to refer to evolution that requires mechanisms other than natural selection acting on variations (or genetic drift) – which he calls Darwinian evolution.
Gould favoured (a), and at first sight it may seem appropriate to opt for a simple descriptive meaning, because it implies an open-mindedness or lack of presumption which is commendable in a scientific context.
However, in fact it makes the term macroevolution redundant and of no explanatory value. What is the point in having a term that means nothing more or less than supra-species? Surely it would be much more useful for macroevolution to be used to describe evolution that requires more than can occur solely by shuffling and selecting subsets of genes.Failings of such a wide range of meaning for ‘macroevolution’
It does not deal consistently with mutations
Which leads to perhaps the most important failing, and I think a key issue – it does not deal consistently or satisfactorily with mutations.
On one hand, by using macroevolution to refer to any evolution above the species level there is no doubt that this includes evolution that is due entirely to differential segregation of genes present in an initial population (e.g. Galapagos finches). That is, it clearly includes evolution that does not involve any mutations.
But on the other, ‘macroevolution’ is used universally to refer to the evolution of organisms with substantial new structures – such as eyes, limbs, flowers, and body plans – that would necessarily require (many) new constructive genes (which are presumed to arise by mutation).
Hence, by using macroevolution so broadly it does not distinguish between at least two fundamentally different degrees of evolution.
Not only does it not distinguish, it militates against clear thinking about what processes are occurring. Indeed, it seems to me that:
Either many biologists do not actually perceive the substantial difference between (a) evolution that is due solely to the segregation of genes and (b) evolution that requires new genes; and hence do not appreciate the loose way in which they are using 'macroevolution'.
Or they do see it, but are deliberately using ‘macroevolution’ loosely in order to provide at least semantic support – because biological evidence is lacking – for the view that macroevolution is nothing but accumulated microevolution (discussed below).
This lack of clear understanding is illustrated – and fostered – by the way in which evolutionary textbooks treat migration and mutation as equivalent (as sources of genetic diversity) when in fact they are fundamentally different.
In this context, migration refers to the situation where one population of a species receives an influx from a group of individuals of the same or similar species. The group of migrating individuals has a somewhat different genetic constitution from the receiving population, so the combined population has greater genetic diversity.
Because mutations alter genes – even if only by corrupting them – they, too, increase genetic diversity. (See here for example(s) of morphological variability introduced by corrupting genes.)
So both mutation and migration increase the genetic diversity of a population, and it is in this sense that they are treated as equivalent.
However, there is a clear and fundamental difference between them:
In one case migrants introduce functional genes into the receiving population (perhaps re-introduce genes that had previously been lost by selection).
But in the other it cannot be assumed that mutation introduces functional genes. In fact the evidence is quite the opposite: the vast majority of mutations are known to be deleterious, or at best neutral, with very little if any evidence for mutations giving rise to new useful genes.
But it seems that either this distinction is not perceived, or mutation is deliberately conflated with migration to try to provide support for the view that mutations do produce new genes.
Not only does the use of macroevolution in this broad or loose way militate against clear thinking, it is also likely to mislead. That is, using ‘macroevolution’ to include evolution that involves only the segregation of existing genes, for which there is ample evidence, all too readily gives (or even is deliberately used to give) the misleading impression that there is evidential support for evolution that would require new genes. Indeed some biologists argue that the whole of evolution of life on earth is merely an extrapolation of changes such as in the moths or finches. But this is completely false, needs to be recognised as such, and challenged.A more meaningful definition of macroevolution?
It will be clear from the above comments that I think a significant distinction exists, and should be recognised, between evolution that is due solely through the selection and segregation of pre-existing genes, and evolution that involves new genes.
Some will argue that the distinction is of little or no significance – because both are part and parcel of the overall evolutionary process(es). However, for this to be valid would require that new genes are produced at a rate that is comparable with the production of new variations by mixing/segregating existing genes.
But it is evident that there is a huge disparity: whereas new gene combinations (and corresponding morphological variations) are produced (in abundance) every generation, new genes arising by mutation are so rare that evolutionists struggle to find examples of them. Although mutations are reasonably frequent (typically 1 in a billion per nucleotide per generation), the production of useful /constructive new genes (not merely corrupted ones) is exceedingly rare.
This fact alone should be sufficient to justify using the production of new genes as being a much more meaningful threshold for ‘macroevolution’ than its usual current usage. And all I’m advocating here is that we should reserve ‘macroevolution’ for evolution that has involved the production of new genes. Not only would this make the term more meaningful, it would also promote better scientific scrutiny and understanding of evolutionary processes.
In other words it would make much more sense if ‘macroevolution’ were based not so much on degree of morphological change, but on genetic change, specifically the occurrence of useful new genetic material (e.g. new functional genes).
It is also clear that too many biologists do not think clearly about what is happening in any particular instance of evolution, and the use of a common term ‘macroevolution’ to describe a wide range of levels of evolution fosters that unclear thinking.
Unfortunately, I wonder whether the vagueness of use of ‘macroevolution’ is also promoted by some partly in order to discourage clear thinking about what is happening – because clear thinking would highlight the problem of the origin of new genetic material, and thereby expose a fatal flaw in the theory of evolution.Is macroevolution just accumulated microevolution?
Most biologists probably follow Darwin’s view that evolution proceeds through a long series of small changes each of which can occur readily – not through exceptional large-scale jumps; i.e. that macroevolutionary changes are effected through the successive accumulation of many small (microevolutionary) steps.
Ernst Mayr (1904-2005)
Indeed, for some, that macroevolution is reducible to accumulated microevolution is an a priori tenet of evolutionary doctrine. For example, here is Ernst Mayr, according to Gould the ‘prime architect of modern neo-Darwinism’  :
The proponents of the synthetic theory [of evolution] maintain that all evolution is due to the accumulation of small genetic changes, guided by natural selection, and that transspecific evolution is nothing but an extrapolation and magnification of the events that take place within populations and species. 
It is non-negotiable, because otherwise it could undermine evolution as an exclusively naturalistic theory.
However, we need to examine the evidence, which requires careful consideration of the different processes taking place in evolution (which all too often are conflated):
There are 3 key processes to evolution:
- The production of genes (which provide genetic variability) – presumed to arise by essentially random (undirected) mutations.
- The production of variations – by mixing the available genes in the course of reproduction – again, essentially random, though with limitations depending on e.g. the location of genes within the genome.
- The selection of favourable gene combinations (those associated with favourable phenotypic variations) – which is not random, but probabilistic (statistical) based on generally enhanced survivability and reproductivity of individuals having favourable variations; i.e. this is natural selection.
The evolutionary position regarding microevolution and macroevolution can be summarised as follows:
- Evolution is substantially true, so all 3 processes are ongoing, more-or-less simultaneously; successive instances of microevolution will accumulate and naturally lead to macroevolution, i.e. microevolution and macroevolution are a continuum.
- It is generally thought that either a species changes gradually until it is sufficiently different (from some starting point) that it is considered a different species (anagenesis), or different populations of a species diverge gradually until they are sufficiently different from each other to be considered separate species (speciation).
Either of these may involve segregation of existing genes and/or production of new ones – it does not matter which – so, again, macroevolution will emerge from successive accumulated microevolution.
- There is ample evidence for (2) and (3) which are dependent on the existence of genes; so it is reckoned /presumed that (1) must also occur.
- In addition, (1) and (2) are often conflated because both are random (and contrasted with non-random natural selection). Notably by Ernst Mayr who frequently stressed that evolution entails 2 steps:
- random generation of variations (by mutation and genetic processes, he lumped them together), and
- non-random selection.
And, as there is ample evidence for (ii) this misleads many into thinking that there is also evidence for (i) – without considering the significant difference between (1) and (2) above.
A key assumption of this widely-accepted view of evolution – which treats evolution due to segregating genes and evolution requiring new genes as comparable – is that new genes will arise reasonably readily and frequently – at a rate that is comparable with the production of new variations by the mixing and segregation of existing genes. Yet, as mentioned above, this is patently not the case.
So it is also clear that the evolutionary dictum that macroevolution is just accumulated microevolution is advocated for essentially ideological rather than empirical reasons. And it is maintained by not looking too carefully at the scientific evidence – specifically, by presenting evolution that is due to mixing and segregating existing genes as if it were evidence for evolution through the acquisition of new genes.
Finally, whether or not the usage of 'macroevolution' changes along the lines I am suggesting, it is incumbent on biologists at least to recognise the different processes that occur in evolution, and to stop using loose usage of 'macroevolution' as a semantic argument to try to extrapolate from evolution that involves only the segregation of existing genes to justify evolution that involves the production of new genetic material.
Notes display in the main text when the cursor is on the Note number.
1. Peter and Rosemary Grant, 40 Years of Evolution: Darwin’s Finches on Daphne Major Island, Princeton University Press (2014).
2. See https://en.wikipedia.org/wiki/Liger and https://en.wikipedia.org/wiki/Tigon . Image by Hkandy (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons.
3. For example see https://en.wikipedia.org/wiki/History_of_evolutionary_thought.
4. Buffon, Natural History, Vol. 3. Section ‘The natural history of the ass’, http://faculty.njcu.edu/fmoran/vol3ass.htm
5. Painting by François-Hubert Drouais [Public domain], via Wikimedia Commons.
6. Blind Watchmaker, chapter 9 (p247); emphasis in the original.
7. Stephen J. Gould, ‘Macroevolution’, in Encylopedia of Evolution, Vol. 1, Oxford University Press, (2002) p E-24.
8. Image from https://he.wikipedia.org/wiki/%D7%A7%D7%95%D7%91%D7%A5:Stephen_Jay_Gould.jpg , available under Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) https://creativecommons.org/licenses/by-sa/4.0/legalcode, via Wikimedia Commons; no changes made.
9. For example, The Princeton Guide to Evolution, Princeton University Press (2013), Section IV ‘Evolutionary processes’, p305.
10. For example, Mark Ridley, Evolution, 3rd Edition, Wiley-Blackwell (2004), p54 ‘For instance the long-term persistence of the processes we have seen in moths and salamanders could result in the evolution of life.’
11. Stephen J. Gould, ‘Macroevolution’, in Encylopedia of Evolution Vol. 1, Oxford University Press, (2002) p E-25.
12. E. Mayr, ‘Species and transspecific evolution’, in Animal species and evolution, Cambridge, Massachusetts, (1963) p586.
13. Image by University of Konstanz [CC BY 2.5 (http://creativecommons.org/licenses/by/2.5)], via Wikimedia Commons.
14. For example in E. Mayr, ‘Evolution’ in Scientific American, 239 (3) September 1978, p44.‘Evolution through natural selection is (I repeat!) a two-step process. The first step is the production (through recombination, mutation and chance events) of genetic variability; the second is ordering of that variability by selection.’
Page created February 2017; last revised April 2017.