When Charles Darwin wrote his infamous book, On the Origin of Species, he was attempting to explain why and how new species develop. In a sense, it was a reactionary book, reacting to many of Darwin’s contemporaries believing that species existed in an unbroken line from creation with no changes. Over 150 years later, the idea of speciation remains an active, and sometimes controversial, area of biology.
Over 150 years later, the idea of speciation remains an active, and sometimes controversial, area of biology.
Speciation is particularly relevant to creationists because a common evolutionary argument is that Noah could not have fit all the extant species on the ark. Given there are 6.5 million named species1 and as many as an estimated 50 million total living species,2 this criticism would be valid, except for one tiny point. Noah did not take every species on the ark. The Bible makes it clear that Noah took kinds (Hebrew min) on the ark (Genesis 6:19–20). The misunderstanding arose from Carl Linnaeus’ classification system.
Linnaeus, in his attempt to standardize biological classification, shortened names down to what we know today as genus and species. However, these were not originally English words. Both came from Latin. Species, as it turns out, happens to be the Latin word for kind, something even evolutionists do not dispute.3 When Linnaeus made his classification scheme, he thought he was classifying the biblical kinds. However, Linnaeus, as he learned by the end of his life,4 was in error. The species is not the level of the biblical kind. Often creationists estimate this to be about the family level on the Linnean hierarchy.5
Because of Linneaus’ error and the obscure nature of his later self-correction, many in Darwin’s day mistakenly believed that the species was a fixed, unchangeable category and that God had made it so. This myth propagates to this day on the internet, in part because it benefits willingly ignorant or deceptive skeptics in generating clicks and revenue for social media. Anyone who has done their homework knows that creationists do believe that new species form. Even when Linnaeus believed in a fixed species, he believed varieties within them could arise.6
Some atheists and theistic evolutionists in academia7 have armed themselves with slightly more knowledge of what creationists believe and accuse creationists of believing in so-called “hyper-evolution.”8 Perhaps surpisingly, they claim creationists believe in evolution, just evolution that happens very quickly. Of course, this is just as poorly researched an promulgated as the fixity-of-species claim. It assumes evolution means change over time, which creationists have never rejected. Biblical creationists just believe change has limits, and evolutionists don’t. Further, the required rate of speciation since the flood is not nearly as “dire” as presented. If one new mammalian species arose every 200 years, most mammalian families would be easily accounted for. Only a handful would still need to be explained.9,10
The irony is that the evolutionists themselves have discussed the observed extremely rapid formation of species. In a 2017 article on Galápagos finches, the authors pointed out that a distinct inbreeding lineage formed in just two generations!11 Galápagos finch generations are only a few years long at most, not 200 years. Perhaps the academics should read more academic papers?
The development of a new species raises the question of what a species is? As it turns out, this is a harder question to answer than it appears. There are a proliferation of species concepts in existence, with one expert writing a book claiming there were at least 32 separate species concepts.12 That was over half a decade ago. More concepts have likely been proposed since then. With the advent of phylogenetic-based taxonomy, some scientists have advocated rejecting the idea of species all together, to focus purely on the evolutionary clade.13
The definition of species most people learned in high school, and the one most scientists default to, comes from Ernst Mayr. Known as the biospecies, Mayr defined it as “groups of interbreeding natural populations that are reproductively isolated from other such groups. Alternatively, one can say that a biological species is a reproductively cohesive assemblage of populations.”14 Importantly here, Mayr does not mean that hybrids cannot form between two species. Rather, he means that when hybrids form, they will not “disintegrate the genetic integrity of the species”.15 If we assume Mayr’s definition is absolute (though it is not: asexually reproducing organisms do not fit well in the model), then we are left to discuss how speciation occurs in the wild.
There are four primary modes of speciation: allopatric, peripatric, parapatric, and sympatric.16 Allopatric speciation is the model most are familiar with. This model calls for a geographic separation of some kind between populations. This geographical separation need not be measured in miles or even feet. Using different aspects of the same habitat can be enough in some instances.17 On the other hand, long geographical dispersals of larva do not guarantee mixing between related species. One coral reef fish group has genetically distinct populations, despite its larva dispersing for thousands of miles on ocean currents.18 Somehow, the members of the same species end up in the same places generation after generation. However, different habitats are not necessarily required. If two populations in identical habitats are separated by a large enough gap, unpassable to the species in question, new species may form in one or both populations.19 This formation is often assumed to be the result of differential selection pressures, though this has been questioned.20 Allopatric speciation is probably also the easiest to understand and the least controversial. The other three tend to generate more controversy.
Sympatric speciation is probably the most hotly debated, though at least a few examples are accepted.21 The early practitioners in the field of speciation largely rejected sympatric speciation, but the pendulum has swung back toward the idea in more modern times. According to the theory, within populations males and females mate preferentially due to something called sexual selection. This process of mate choice makes mating nonrandom, meaning that males and females are selecting each other on the basis of some preferential trait, something called assortative mating.22 If assortative mating persists within a population, new species can form within a population.23
In practice, sympatric speciation is much harder to define. One review of the topic gave three major ways to determine if sympatric speciation has occurred, though they admit there is some subjectivity to the criteria.24 One way that is commonly thought of as sympatric is host-switching speciation. This is often thought to occur in parasites, where a particular parasite, for whatever reason, finds a novel host. Its offspring then infect said host and other members of the host species and only breed with parasites that use the same host. Over time, a new species of parasite forms.25,26 While this sounds simple enough, there are significant difficulties in using this as a surefire example of sympatric speciation. As the aforementioned review points out, parapatric speciation may also account for host shifting, as may colonization.27 The ambiguity around sympatric and parapatric speciation has led some researchers to suggest abandoning the attempt to spatially determine species and instead focus on the natural forces that cause divergence.28
Parapatric speciation is similar to allopatric speciation except the two populations diverge while continuing to interbreed, leading to a hybrid zone between the two.29 Simulations suggest that parapatric speciation can occur rapidly, within a few hundred generations.30 In something with short generation times, this could be less than 100 years. Usually, the model requires that the populations be isolated from each other, with small amounts of migration between the two, but with hybrids less viable than normal members of either population.31 There are some examples described of this type of speciation, usually supported by morphological and genetic evidence.32 Also, ecological evidence is sometimes considered.33
As noted before, there are some issues with defining parapatric speciation as well.34 Because most speciation happened historically, there is also the difficulty in determining whether the historical event was parapatric or allopatric, with the populations coming back together after speciation. One study of four species of closely related shrub found that allopatric speciation was more likely the cause of their speciation and that they had come back together afterward.35 Thus, the importance or commonality of parapatric speciation is open for debate.
Peripatric speciation is similar to allopatric speciation, except one population is considered peripheral to the major population and is much smaller than the main population. In such a small population, once it is isolated from the main population, speciation could occur relatively easily, provided the small population contains at least one divergent trait (preferably more) from the main population. The divergence of small populations from their source is called the founder effect, which means that these new populations usually have less diversity than their parent populations. Since some parental population options are lost, previously variable traits become fixed. While direct founder effect speciation is considered rare,36 peripatric speciation makes use of this principle indirectly by having a small peripheral population becoming the new species. There are some proposed examples of this form of speciation, including in prairie dogs,37 plants,38 and hermit crabs.39
Like other forms, there are difficulties in delineating peripatric speciation. Further, the models in which the new population loses a trait that is normally selected for sexually fails because the selector retains preference for the original trait.40 There is also the difficulty of increased genetic load brought about by the smaller population size and the accompanying inbreeding, making peripatric species potentially weaker than their forebearers.41 It is important to note here that just because these speciation scenarios have issues does not mean speciation did not occur. Creation is very complex, and no models (especially when hampered by evolutionary assumptions) are able to simply and correctly account for all the required parameters, and the historical nature of most speciation makes analysis difficult.
As animals spread from Ararat, new species would have emerged naturally as species moved away from each other.
In a post-flood scenario, speciation likely occurred in a relatively linear pattern.42 As animals spread from Ararat, new species would have emerged naturally as species moved away from each other and into varying habitats. The founder effect would have had a significant impact on these new populations. Variable alleles would have been uncommon in these original small populations. Due to genetic drift associated with the founder effect, fixed traits would have appeared quickly in populations, making them differentiate relatively easily.43 Each of these new populations likely could interbreed with their close relatives, at least in the beginning, resembling a peripatric model, except for both populations initially being small. As populations dispersed into new habitats, environmental pressures would fix even more traits, further diversifying the population until it either no longer could or no longer wished to regularly successfully interbreed with other related populations. Thus, in a very short space of time after Ararat, possibly only a few years for short-generation kinds, there would begin to be distinct species.
Rapid speciation as a process is in perfect accord with the creation model. In fact, it is exactly what creationists would expect if the Bible is true. While the specific details of the process are open to debate, the fact that it happened is indisputable, and it matches the biblical model perfectly.