Friday, 24 September 2010

The definition of kinds

Recently, as I’ve been working with animal remains, I’ve become increasingly aware of the difficulties creationist thinkers have with defining the word “kind”. They use it a lot to try and get round the problem of speciation. Most creationists try and use it to suggest that animals can speciate within their own kind, but no further, so fish cannot evolve into an amphibian and no matter how many pennies you get, you can’t make a pound. Now the many problem with this is that they never define what a “kind” is. In one topic, I discussed with a creationist, he came up with three definitions, a genus, a biological family and types of enzymes. This short essay attempts to show why the current terminology for taxonomy is adequate for its task and that the concept of “kinds” used by creationist thinkers is fundamentally flawed and has no bearing on taxonomy.

Firstly, let us deal with the idea that a kind is a species. Unfortunately for creationists this is disproven by numerous account of speciation. For example here are a few papers which document these events in both the lab and the wild:

A Molecular Reexamination Of Diploid Hybrid Speciation Of Solanum raphanifolium by David M. Spooner, Kenneth. J. Sytsma and James F. Smith, Evolution, 45(3): 757-764 - DOCUMENTATION OF AN OBSERVED SPECIATION EVENT

Chromosome Evolution, Phylogeny, And Speciation Of Rock Wallabies by G. B. Sharman, R. L. Close and G. M. Maynes, Australian Journal of Zoology, 37(2-4): 351-363 (1991) - DOCUMENTATION OF OBSERVED SPECIATION IN NATURE

Evidence For Rapid Speciation Following A Founder Event In The Laboratory by James R. Weinberg Victoria R. Starczak and Danielle Jörg, Evolution 46: 1214-1220 (15th January 1992) - EXPERIMENTAL GENERATION OF A SPECIATION EVENT IN THE LABORATORY

Evolutionary Theory And Process Of Active Speciation And Adaptive Radiation In Subterranean Mole Rats, Spalax ehrenbergi Superspecies, In Israel by E. Nevo, Evolutionary Biology, 25: 1-125 - DOCUMENTATION OF OBSERVED SPECIATION IN NATURE

Experimentally Created Incipient Species Of Drosophila by Theodosius Dobzhansky & Olga Pavlovsky, Nature 230: 289 - 292 (2nd April 1971) - EXPERIMENTAL GENERATION OF A SPECIATION EVENT IN THE LABORATORY

Founder-Flush Speciation On Drosophila pseudoobscura: A Large Scale Experiment by Agustí Galiana, Andrés Moya and Francisco J. Alaya, Evolution 47: 432-444 (1993) EXPERIMENTAL GENERATION OF A SPECIATION EVENT IN THE LABORATORY

Pollen-Mediated Introgression And Hybrid Speciation In Louisiana Irises by Michael L. Arnold, Cindy M. Buckner and Jonathan J. Robinson, Proceedings of the National Academy of Sciences of the USA, 88(4): 1398-1402 (February 1991) - OBSERVATION OF A SPECIATION EVENT IN NATURE

Attempting to claim speciation does not occur is therefore foolish and displays an ignorance of biology. The fact that creationists working in the field of Baraminology have not settle on this definition shows that they to find this problematic.

Another proposal is that a “kind” is a genus. Now, to me, working with animal remains and having to look up their names, the problem is already apparent. Let us look at the Pig Family or Suidae. Now the domesticate pig and Wild Boar are in the same genus (Sus), however, the Warthog genus (Phacochoerus) isn’t. Therefore, even creationists cannot accept this proposal as acceptable as according to them, they are “pigs”. The same also applies to the Cheetah, (Acinonyx jubatus) which is not part of the Panthera genus of lions, leopards, tigers and jaguars yet is clearly a big cat and related to them. Therefore this concept of “kinds” being the equivalent of the genus is wrong.

Concerning the biological families, this backfires on creationists spectacularly again. If we consider the Homindae family, this contains us, chimps, gorillas, etc. If we ask any creationists, I’m sure they will deny that we have a common ancestor with chimps nor that we belong in the same kind as them! This renders their concept of “kinds” as being unable to apply to their own standards.

Furthermore, with the two above definitions, scientists have come up with them for specific purposes. In taxonomy terms, genus and family have specific meanings and this alternative idea, “kinds” serves no purpose. Genus and Family are used to describe how closely related species are according to traits, both physical and genetic. This leads to a system which accurate describes how closely related modern species are to one another. Whilst it is very good at this, it is not so good when referring to past specimens such as Australopithecus, Ardipithecus and this has led to researchers in this field to describe the system as imperfect (taken from a seminar with Terry O’Connor). As a system it is not good at showing how one genus may evolve out of another (for example, Homo from Australopithecines), nor is it completely reliable when we examine extinct species such as Homo habilis (which may or may not be a species). However, this may be due to Linnaeus purposefully designing a static system as he was unaware of Evolution (Holmes, 2009, Pg 48). 

Another suggestion from creationists is that a kind could be:
“Taxonomically, a kind is a group of organisms that share a basic set of exclusive synapomorphies. Members of the same kind, usually, should be able to interbreed although the resulting offspring may prove to be infertile.”
Taken from here

Now let us look at the Big Cats again, especially from the genus Panthera. In this case, Lions and Tigers definitely can interbreed and so can Lions with Leopards and Jaguars, in fact all of them can with one crucial exception. Leopards and Tigers have all be noted to have never produced any living hybrids. Furthermore, Leopards can produce hybrids with Pumas, a Pumapard. So is the Puma included into this “kind” despite the fact it can’t mate with anything else in the Panthera genus? What about the Wholphin? It is clear that by using the word “kind” in this context would seriously confuse taxonomical issues and would be impossible to use. Furthermore, this is not delving into the term Synamorphy which confirms Evolutionary theory concerning common ancestry.

The problem encountered with the Big Cats also arises with the Larus Gull. This genus is known as a Ring Species. Does that mean that these species are all the same kind?

In general the concept of “kinds” is wrong on various grounds mainly:
1. There is already established words for taxonomy.
2. No creationists can define the term in a rigorous fashion that is of benefit for taxonomy.
3. Animals interbreed in such a variety of ways and produce various hybrids that defining a category for “kind” is near impossible.
4. It admits the possibility that humans could have evolved from an earlier version (which no creationist will admit to) defeating their argument.

With this in mind, we are then directed back towards the normal methods of taxonomy, using definitions of species, genus, etc. Whilst there is some debate occasional about what constitutes as a species, (see the species problem) the system allows the definitions to be rigorous and furthermore provides more precision than “kinds”. Furthermore, it can be adapted from its original static state to show the evolutionary past of a species at the present moment in time. The subclass Elasmobranchii, which includes Skates, rays and sharks, indicates that these fish are more closely related to each other than a shark would be to a rabbit fish. These members of the class Chondrichthyes would be more closely related to each other than another member from the Infraphylum Gnathostomata (vertebrates with jaws) such as a crocodile.

Therefore, whilst the current system of taxonomy can obscure the fluidity of Evolution at the same time it can provide a great aid in deducing the relationships and connections between current species, genera, etc. The current system provides a service for biology that Baraminology, the creationist study of what constitutes a “kind”, cannot provide.

Holmes, R., (2009) The Age of Wonder,  Harper Press UK

Interesting articles

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