On Biblical Kinds
December 19, 2014
There are several alternative hypotheses offered by theists to counter the scientific theory of evolution. These tales of special creation generally posit that all organisms on this planet were placed here, in their current form, by a supernatural entity. Perhaps the most familiar of these is the idea of Intelligent Design (ID), which has been put forward as scientific, and worthy of inclusion in science classrooms. ID is a Christian concept, based largely on literal interpretations of the Bible, though it does not necessarily restrict itself to a young (6000-year-old) Earth.
The basic concept of Bible-based creationism is that the major groups of living organisms on this planet appeared on the fifth and sixth days, as described in the book of Genesis in the Bible. Since then, the mechanisms of Evolution—specifically microevolution—have taken place within these major groups, resulting in the diversity of species within these groups we recognize today.
These major groups of organisms are referred to as “kinds” in the Christian creationist model. “Kinds” are different groups of organisms that seem intuitively distinct from other groups. For example, horses, donkeys, and zebras may belong to a single kind, the horse kind. There is a dog kind, that includes wolves and coyotes, too, and foxes for good measure. There would be kinds of trees, like oaks or maples. The assumption is that from these basic kinds comes all the modern diversity, like pin oaks, live oaks, and scrub oaks. All of life is thus divided into the kinds that originated at Creation.
Advocates of Biblical creationism stress that the “kinds” are unique, and that there are no intermediate forms to be found between them. Further, they believe that kinds can be proven to be real using scientific methods.
So a “kind” is the basic division of organisms according to Creationists, in much the same way that “species” is the fundamental division of organisms to evolutionary biologists. The theory of evolution explains how evolution occurs within species, and over vast amounts of time, results in new species. Over even longer periods of time—millions or billions of years—new larger groups of organisms, similar to kinds, can evolve. The origin of these new, larger groups is a process called macroevolution. Proponents of biblical creation claim that macroevolution is impossible because the kinds are distinct and always have been. No new kinds have ever arisen since they were created.
So, then, what is a kind?
I’ve asked this question more than once, most often to students wishing to explore the Creationism vs Evolution debate. I’ve never gotten a very satisfying definition. In February of 2014, Ken Ham (Creationist and Founder of Answers in Genesis) finally provided a working definition during his debate with Bill Nye. Ham said that kinds are groups of animals at about the same level of scientific classification as “family.”
Family is a scientific term in the field of taxonomy (the science of naming and classifying organisms) that is a group that includes many species, both closely related and more distantly related. For example, the family equidae includes horses, zebras, and donkeys. The family canidae includes dogs, and coyotes, and wolves. It also includes foxes, which are more distantly related and not in the genus canis. There’s the familysuidae, the pigs. Peccaries are pig-like, but wait, they’re in the family tayassuidae. Hm. Well, they’re both in the suborder suina, so maybe that’s what Ham meant when he said ‘about the same level as family.’
At a first pass it seems, at least with commonly known organisms (focusing on mammals), that this idea that a biblical kind could be roughly equivalent to a scientific family.
Let’s back up, because there’s a falsehood here. Just because taxonomic nomenclature is used by scientists, doesn’t necessarily mean there isn’t some arbitrariness there. The scheme that includes family was created by Linneaus in 1751. Families in the Linnaean sense were groups of animals that seemed similar enough to each other to be related. But there was no biological basis for this. It was just done that way because it felt right. It is rather subjective, and based, to a large degree on what seems right—just like the concept of kinds.
As science has progressed, it has become clear that many of the groups proposed by Linneaus are arbitrary. In fact, as we’ve come to understand biological evolution, scientists are using Linnaean nomenclature less and less for discussion of evolution. Instead, scientists opt to use more rigorous methods, like cladistic analysis, to explore evolutionary relationships. Linnaean taxonomy merely hangs on as a convenient way to name and categorize organisms, but it is no longer used to support actual relationships between organisms.
The only place where Linnaean taxonomy retains a strong foothold (and for how much longer one cannot be sure) is in the naming of species. Species is the only Linnaean rank with a specific and clear definition. In biology, it is required for a species to be able to reproduce with other members of its species and produce viable fertile offspring. Every other grouping is made for convenience, and the ranking (genus, family, etc.) is determined based on the researchers subjective determination of how similar or different groups are from one another.
Higher ranks (genus, family, order, etc. all but species) are subject to change. The definition of such a group may be revised. Its rank may change. The members of the group may be changed. Most often, such things happen with either the discovery of new species, or due to new methods for determining relationships
Take, for example, the mustelidae—the weasel family. Traditionally skunks, minks, weasels, badgers, otters, and wolverines are in this family. They do look a lot alike, low to the ground, long in body, carnivorous, smelly. But genetically, skunks are distinct. In fact, they are more different genetically from the other members of the mustelidae than are seals and raccoons, which clearly are not mustelids.
Or take, for another example, the matter of the giant panda (Ailuropoda melanoleuca). There has been a lot of discussion in the biological community about whether or not the giant panda is a true bear, and should be assigned to the family ursidae with all the other bears. It certainly looks bear-like, hence the colloquial name of ‘panda bear,’ but it also is fully herbivorous which is notably not-bear-like. That might be just fine, given that although the family ursidae is within the order carnivora, the carnivorous mammals, the only fully carnivorous member of the ursidae is the polar bear.
Giant pandas share much in common with both bears (family ursidae) and raccoons (family procyonidae). Based only upon physical characteristics alone (not all of which are obvious to an untrained observer), we couldn’t really be certain to which group giant pandas belong. These are two very different groups of mammals that are clearly distinct (as ‘kinds’ are supposed to be), and the giant panda could go either place. For what it’s worth, we’ve learned that pandas are properly bears, based on DNA analysis (see O’Brian et al., 1985).
Red pandas (ailurus fulgens) have suffered similarly. They are definitely not bears, but may or may not be related to raccoons. Again, genetic evidence provides the solution and places them in their own family separate from raccoons and bears (O’Brian et al., 1985)
We know about the flexibility, arbitrariness, and inaccuracies of taxonomic groups as practicing biologists and paleontologists. But for the general public it's not so clear. Evolution is not well taught in classrooms around the nation. All students are given is Linnaean taxonomy, and the impression that it’s the most scientific thing out there. So of course it sounds really scientific to say kinds are at the same level as family to everyone except those who really understand biology.
To biologists, to say that kinds and families are equivalent is to say that kinds are completely arbitrary and grouped according to whatever feels right. This is no improvement over the definitions I’ve gotten in the past and is still unsatisfying.
But at least it sounds science-y and tastes pretty good, like the bologna that it is.
The point to all of this is that the term “kind” is still poorly defined. Saying it’s at about the level of family seems helpful and valid; however, the concept of a family in the Linnaean sense is amazingly arbitrary. These are defined as groups of animals that seem to be related to each other—which is basically the same as the definition of a kind in the first place.
When tested rigorously using cladistic methods, and even only on modern organisms, the arbitrariness of all the Linnaean ranks becomes clear. They’re not about collecting certain numbers of species into convenient groups. They’re not about separating groups from each other that have a certain amount of genetic differences. It’s a relict system that holds on because it does allow scientists to communicate with each other—provided all understand the pitfalls of using the system. But you need only sit in on one nomenclature session at a paleontology meeting to see how poorly it works for establishing actual relationships between organisms.
And we still lack a satisfactory definition of “kind.”