Fluidity of Species

Recently I published an article on the concept of missing mutations.  This article apparently triggered evolutionists because it led to more activity on my twitter page than I usually get in a month. As part of the annoyingly character limited debate that ensued, one of the evolutionists I was debating attempted to force the fixity of species argument on me.  Since the evolutionists attempted to pinion me with an argument I was not making, this article will attempt to clarify what a species is, why they can change, and why kinds and species are not interchangeable terms.

The example I gave in my twitter debate which led to evolutionists attempting to foist fixity of species upon me was that of a lion and a tiger interbreeding. When such an event, rare though it is, occurs, the offspring is referred to as a liger or tigon.  Evolutionists in the debate objected to the example, correctly pointing out that a lion and a tiger are different species.  The intent was to pin me into an old concept called the fixity of species.  The fixity of species concept is an old, false idea which stated that species did not change. While false, there was a time when many creationists did hold this position and evolutionists have not forgotten this fact.  However creationists are not the only ones guilty as we shall see in a moment. This erroneous position originated as a poorly conceived attempt to fit the Linnean classification system into the Bible. Creationists took the word “kind” in the first chapters of Genesis and made it equivalent to the word “species” in Linnean classification. However, kind and species are not the same as we will demonstrate shortly, and thus the concept was fatally flawed from its origin.

The above paragraph begs the question of what is a species? The answer to that is scientists are not entirely sure. The respected science periodical Nature defines species this way:

“A biological species is a group of organisms that can reproduce with one another in nature and produce fertile offspring. Species are characterized by the fact that they are reproductively isolated from other groups, which means that the organisms in one species are incapable of reproducing with organisms in another species.”

Note the last sentence. That is fixity of species in a nutshell.  This is also patently and demonstrably false.  Any quick google search will confirm the existence of ligers and tigons and that they are the result of breeding a Lion (Panthera leo) with a Tiger (Panthera tigris). The point Nature misses which leads to this error is the meaning of reproductive isolation. It does not mean incapable of reproducing with other species. Rather the term refers to populations which are either unlikely to or do not naturally reproduce with another population, such as tigers and lions.  UC Berkeley has a better definition on their website which goes as follows: “A species is often defined as a group of individuals that actually or potentially interbreed in nature” However, while more accurate than the Nature definition, this definition is actually too broad.  Evolutionist Ernst Mayr proposed a definition in the mid twentieth century that perhaps works best. The definition essentially says that species are populations of similar organisms which interbreed with each other but are reproductively isolated from other populations.

The fact that the previous paragraph was required to establish a definition of species should inform you that species is a somewhat fluid concept.  Take for example the Guppy, known to science as Poecilia reticulata and the Endler livebearer, known currently as Poecilia wingei. For years the Endlers livebearer was considered a subspecies of guppy. However, recently it has been elevated to a separate species. The fishes genome and habitat did not change.  What changed was the scientific consensus.  Are guppies and Endlers livebearers the same species? Perhaps but current evidence suggests otherwise.  However this example shows just how fluid the concept of species is. 

Since species is such a fluid concept, change between species is both normal and inevitable. Take the above example of guppies and Endlers livebearers.  Whether Endlers livebearers ever are reclassified as guppies or not, both fish trace their ancestry back to a population of guppy-like fish. The two species arose due to naturally occurring expressions of differences in the genome in separate populations.  This fluidity of species permits changes within populations to produce new species. This process is known as speciation.

Unlike species, kind is a rigid concept. In Genesis 1, God lays out the concept of reproduction after its kind. Every creature and plant mentioned in the opening chapter of Scripture follows this pattern. The phrasing implies hard limits to possible variations within the kind. If something reproduces after its kind, then there must logically be boundaries it cannot cross, else it becomes another kind. However, these limits cannot be at the species level. If the limit to variation implied by the phrase “after its kind” was at the species level, then species to species hybridization should not occur. Yet, as demonstrated above, such hybrids do occur.  This means that a kind must be found higher up the classification ladder.  Generally speaking, creation scientists set the kind around the family level. However, this is not set in stone across all creatures. Birds in particular tend to be slightly lower than the family level. Regardless, the concept of kind clearly cannot be the same as that of species.

Kind is a term given by God, while species are designed by man. God does not change, but man can and frequently does. While species is a valid concept in the scheme of Linnean classification, it can and does change frequently.  New species arise and old ones go extinct.  However new kinds have never been observed to form. Regardless of evolutionary claims, species change, but are constrained by the boundaries of the kinds and can only change as far as those boundaries permit.