What is a Horse? A Horse is a Horse, Unless of Course it isn’t a Horse

“A horse is a horse, of course, of course, and no one can talk to a horse, of course, unless, of course, the horse, of course, is the famous Mr. Ed!”  From the introduction to the 1960s TV show “Mr Ed”

No one disputes that Mr. Ed was a horse but what about the plains zebra, the quagga, or the donkey?  Too bad they can’t just tell us.   Are these all horses (equines)? What about the 15 extinct species, including the quagga, that taxonomists have assigned to the same genus, Equus, and taxonomists call equines?  And what about the other 30 or more named fossil genera and at least 150 species contained in them that share many similarities with the living members of the genus Equus including horse, donkey and multiple species of zebra? Although similar these other genera and species they also have many significant differences from living equines.   More to the point, when might we conclude that a horse is NOT a horse?  Was an animal that was one foot tall at maturity and walked on feet with four toes a horse or should we call it something else?

These are fundamental questions that taxonomists grapple with on a daily basis.  Those questions include how we define species and how we understand their origins.

The “Horse Series” has been a favorite creationist punching bag

Defining the limits of what make a horse a horse can be challenging to any biologist but it poses some special challenges to adherents of the 20th century American phenomena of young-earth creationism which holds to a 6000 year old earth and creation of living things within the span of six twenty-four hour days.  In the past decade, more and more young-earth creationists (YECs) have embraced lumping large numbers of similar species together and proposed that all members of these groups are a single “kind” and therefore shared a single common ancestor in the past—in this case the very recent past when the kinds departed Noah’s Ark 4350 years ago.  For example, A donkey, a zebra and a horse may appear to be distinct species today but with the creationist’ conception of a kind—sometimes called a baramin—they are all just variants on one created thing that we could call generically a horse. But we might ask, where does this horse “kind” end and another not-horse kind begin? Does this horse kind include all of these other fossil species, none of which are like any of today’s horses but neither are they radically different from them?

The horse series shown in the figure to the right is similar to one that has been used to demonstrate how the fossil record can be interpreted as the history of evolutionary sequence of events that has resulted in our living horse species from a small dog-sized ancestor.   The history is told through a progression of tooth and foot bone changes over 40-50 million years that resulted in the variation that we see today.

For a long time creationist’s, particularly those of the young-earth variety, have, not surprisingly, claimed that this sequence of evolutionary changes from a small common ancestor was a lie.  No such changes could occur but rather the fossil horses represented separately created species.  These fossil species were believed to represent different kinds of animals that were caught up in a global flood and deposited in rocks and deferentially sorted by size from smaller to larger in upper layers.   Over and over again the horse fossil series has been held up as an example of a fanciful speculation of evolutionists.

For regular readers I may sound like I’m beating a dead horse.  Yes, this is another story of how YECs have been gradually changing their public messaging with respect to speciation and common ancestry.  What we will do here and in the next  couple of posts is explore what YECs call the study of the origin of species which they call baraminology (see here for more:  Thoughts on Baraminology).

I expect that for most lay Christians who believe the earth is young, when they hear the term species they think of animals like a zebra and a horse or a wolf and a red fox and they equate these with species of animals God created on the 6^th day of creation.  I certainly remember images from Sunday school of the Garden of Eden with Adam naming animals that look just like the animals that we see around us today such as zebras, donkeys, penguins, lions etc….  But, while the average fundamentalist Christian may still think that God created the species we see today, leading thinkers in the creation science movement beginning in the early 20th century had already begun to speculate that the organisms that God created during the six days were far more capable of “evolving” than the average church goer common believed.  (See: The Ark Encounter Ancestors: The Increasing Inclusiveness of Biblical Kinds)

While creationists don’t use the term evolution and roundly deny that evolutionary theory has any validity, they have changed and adapted their use of terms such as micro and macroevolution to accommodate greater and greater amounts of evolutionary change to organisms over time.  They have replaced discussion of the origin of species with the so-called Biblical concept of an origin of a kind or baramin.  In their interpretation of scripture, a baramin allows for much greater genetic breadth than does the modern concept of a taxonomic species.  In fact, so much genetic breadth is allowed within a baramin that hundreds of biological species may be encompassed by a single baramin.

YECs often claim that this genetic breadth was the result of massive amounts of genetic variation built into the first created animals.  The variation was then sorted into genetically distinct sets of organisms.  However, I think a significant shift in the creationists’ landscape is happening right now as I see one creation scientist after another hinting that much of this genetic variation may actually come from new mutations even while claiming that “new” information/traits can’t evolve.  In future posts I will provide quotes to back up my assertion that the landscape of creationist’ thinking has been changing and is becoming, dare I say, more evolutionary in its assumptions.

Coming back to our question of when is a horse a horse, in my next post I will look at an  intramural debate  among YECs about the evolutionary horse series.  That debate is about just how much of the evolutionary story can a YEC accommodate to explain the great diversity in kinds of animals.   Look at the image to the right which shows some of the diversity of “horses” in the fossil record and present. Our question for young earth creationists going forward will be this:  Did all these horse-like organisms evolve from a common ancestor and if so what did that ancestral pair on Noah’s Ark look like?  Some young-earth organizations (e.g. Answers in Genesis) now openly suggest that it is true, all of these species evolved from just one species and even just one pair of animals.  That animal was a dog-sized multi-toed animal which stepped off the ark and “evolved” into the horse species we see today.   If this is true, the “horse series” that is presented in biology textbooks is not such a lie after all.  As you can imagine not all creationists are able to swallow such a radical acceptance of speciation from common ancestors but they have had difficulty explaining the features of the fossil record to any satisfaction without resorting to at least some rapid evolutionary action.

In our next post we will look more closely at what we mean by a “species” and how this term is critical to examining the young-earth claims about speciation and their view of the origins of biological diversity.

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Cover photo:  “Wild” Banker horses from the Outer Banks area of North Carolina. These horses were domesticated horses brought here from Europe that then escaped into the wild and have been living along these beaches for possibly as long as 400 years.  Despite living wild all that time they differ only moderately in appearance and genetics from other domesticated horses. Photo: Joel Duff in 2014.