Life is incredibly diverse. Millions of species fill the seas, land and skies of our planetary home. It seems as if there is no end to the discovery of new animals, plants and other life forms. As a biologist who teaches a class about plant diversity, I can always count on discovering a new group of plants that I have never seen before which is always exciting. But what blows my mind even more is the thought that the diversity I witness today is but a tiny fraction of the diversity of life that has lived on this Earth.
We know this because of the vast fossil record. In fact, when we start to realize all the diversity in the fossil record, the organisms alive today can start to seem a bit mundane. And I am not just talking about dinosaurs. Sure, the famous megafauna—T-rex , triceratops, saber-tooth tigers and mastodons— get all the attention. But these are just a small fraction of the fauna, much less the extinct plants, that have lived.
Nearly every day I stumble across an extinct group or organisms I had never encountered before. It is rather exciting to think that I could learn about a new group of organisms every day and yet not plumb the depths of Earth’s biological diversity—aka God’s creative handiwork—during my lifetime.
Recently, I was introduced to a new animal that captivated my imagination. I read about this animal on the blog Twighlight Beasts which highlighted a strange-looking ungulate (hooved animal) whose fossilized remains are only found in South America. This ungulate looked like a cross between a camel, a deer, a rhino (three-hooved feet) and an elephant. It’s the nose in the illustrations that obviously catches your attention. Scientists aren’t sure about the shape of the nose, but given the way the nostrils appear to be connected to the skull surface, they believe that the nose had a significant fleshy projection. This particular animal has been classified as a member of an extinct genus of ungulates named Macrauchenia. An interesting bit of trivia about this animal is that the first fossils of this genus were found by Charles Darwin in South America during his voyage on the Beagle.
These animals aren’t considered to be closely related to any living group of ungulates (eg. horses, camels, pigs, cows, deer etc..). In fact, they are just one of many species of an larger group of extinct ungulates all of which lived in South America except a few species that have also been found in Antarctica.
This got me wondering. Just how many ungulates species are there in South America today and how many have lived there in the past? The short answer: Only a handful today but hundreds in the past.
There are 400+ species of ungulates (hooved animals) alive on Earth today but fewer than 30 of them are native to South America. These include single species of alpaca and llama, a few pigs, tapirs, and several deer.
What about extinct ungulates that lived in South America? That is an entirely different story. This funny long-nosed ungulate I said was just one of many extinct species in a single family. A taxonomic “family” of animals is a grouping of many species that have some similar characteristics suggesting common relationships. The canine family (foxes, wolves, dogs) cat family (lions, tigers, cheetahs and house cats) or bear feamily (pandas, sun bears and polar bears) represent the type of diversity that one would find at this category of classification.
In this single family of ungulates in South America there have been 30 described genera (eg. wolves, coyotes and domestic dogs are all members of one genus) each of which may have 1 to a 100 species. So this family can have a lot of species. But then you need to understand that this family of strange ungulates is but one of 25 described families of extinct ungulates in South America. All together there are around 150 described genera of ungulates in these families. The diversity in these families is amazing, running from large rhino-sized animals to small nimble creatures that would have looked like small deer.
Remarkably, all of these ungulates have only ever been found preserved in South America, with just a few from Antarctica.
If you consider that we only have only been able to examine a tiny fraction of the fossilized material in South America, it is likely that there are at least twice this many kinds of ungulates that must have lived in the past. In addition, there are a few other genera of ungulates that have been identified as fossil ungulates related to groups of living ungulates such as llamas and alpacas.
So, how many species of ungulates have existed in South America? Even if we use a conservative estimate of an average of only five species per genus, that would suggest there have been at least 750 species of ungulates that have lived in South America at some point in time. This number is probably a very conservative estimate. I suspect that paleontologists would predict the number of species of South American ungulates that has lived in the thousands.
This is remarkable, considering the same continent has fewer than 30 native species of ungulates alive today.
What Happened to the Ungulates of South America?
Why are there so many ungulates in South America’s past and yet so few today? The simplest answer can be found in the geological history of South America.
Plate tectonic theory explains how the earth’s crust is divided into separate plates that have moved around. This theory tells us that South America spent a long time isolated from all other continents. After it separated from Africa, it was connected to Antarctica up until about 55 million years ago. After it separated from Antarctica, it spent about 50 million years in isolation before volcanic activity produced the Central American land bridge between North and South America just 3 million years ago. This connection of the Americas allowed from something that has been termed the Great American Interchange. This was a migrations of animals from North America into South America and vice versa
Prior to this interchange, there is no evidence of large mammalian carnivores in South America. There were no bears, cats or canines (like wolves) in South America before three million years ago. Being isolated from the rest of the Earth the mammals there evolved in isolation. Without many other mammalian competitors for resources, and predation by very different carnivores, ungulates and marsupials greatly diversified in South America. These herbivores lived in a very different world with respect to the dangers they encountered. For example, they had to contend with a family a huge flightless birds called the “terror” birds of South America. I’ve written about these in the past (When Flightless Birds Rules the Land: The “Terror” Birds of the New World). Some species of terror birds became so large that they could have become the top predators themselves, though there is still debate in the literature about the behavior of these amazing birds. In addition to the terror birds there were huge crocodiles and a strange group of animals thought to be a sister group to marsupials that included carnivorous members. Some of these animals looked superficially like large saber tooth cats though not related to them.
After the Americas were connected by a land bridge, sabertooth cats, wolves and bears entered into South America. It is not difficult to imagine how they could have very quickly caused the extinction of thousands of mammal species there, probably including the terror birds and other South American carnivores.
Ironically, almost every ungulate native to South America today seems to have come to South America in this interchange, while the many hundreds of species of ungulates that used to occupy the continent all went extinct. For example, the alpaca and llama, which are related to camels and we commonly associate with South America, originally lived in the central plains of North America and then migrated to South America. Later these animals and their relatives went extinct in North America during the Ice Age.
Why did all of South America’s ungulates go extinct while many of the North American ungulates survived? Part of the reason may be that South American ungulates didn’t need to deal with many predators, whereas the North American ungulates had been adapting to life with many predators for millions of years. They already had the skills to live with lions, cougars and wolves and so they replaced the ungulates of South America that didn’t have the ability to live with these carnivores.
Young Earth Creationists (YECs) Have an Ungulate Problem
How would a YEC respond to this scenario of the history of South American ungulates? How could there have been at least 750 extinct ungulates in South America – more than are alive on the whole earth today! – which can be seen in and inferred from the fossil record? I expect that the first response would be to suggest that these fossils represent the remains of ungulates that were destroyed in the Flood.
But here is where the YEC’s ungulate problem begins. Even if these were ungulates buried by a global flood, why are these hundreds of different kinds of ungulates only found in South America? How could hundreds of members of one large group of ungulates, none of which are alive today, all have gotten caught up in a global flood and been deposited in only one place on Earth?
This also raises a further problem for the young-earth hypothesis. There are many different kinds of ungulates—probably at least 25 if we use the YEC definition of “kinds” being roughly equivalent to “families” —that must have been preserved on the Ark. But if that is the case, then all 25 of these families/kids of ungulates went extinct after the flood without leaving any evidence?
But there is a bigger problem. All of these ungulates are found in what the majority of YECs believe are post-flood deposits. In other words, we can infer from their own literature that these fossils were not formed during a global flood but rather afterward, from ungulates descended from their ancestors, who survived on the Ark Most of these ungulate fossils (of Eocene age) are found in rocks that represent the very top layers of the geological column. Some fossils are also found in cave deposits, which also must be post-flood in their origin. So there really is no evidence of any of these ungulates existing until after a global flood in YEC models.
So were did these post-flood ungulate fossils come from? How and why did they all end up in South America, right after a global flood?
The YEC might respond that representatives of each of these kinds of ungulates, maybe 25 pairs, would have departed from the Ark. Collectively, they would have all have made the trek from the Middle East up to the Bering Strait into North America and then down into South America. Along the way, they left no remains and none decided to stay on any other continent. They got to South America and then, and only then, did they rapidly evolve into hundred of species at rates of change that would make an evolutionist blush. Then by the time of the Ice Age just 4250 years ago according to the YEC hypothesis, they all went extinct. In the YEC timeline these animals all had to exist in a time window of less than 300 years from Noahic Flood to Ice Age and that assumes they migrated to South America nearly instantly.
To explain the existence of the ungulate fossils in South America, the above scenario is what a young-earth creationist must accept.
This scenario requires a series of fantastical ad-hoc explanations that only superficially account for some the general facts. The conventional explanation—the one that I described at the beginning of this article—fits the data very well. For example, the strange observation that some ungulate fossils are also found in the Antarctic Peninsula. Independent data from plate tectonics tells us that these two continents, South America and Antarctica, had a connection in the past and so fossils of very similar ungulate species found on both continents are not that surprising.
Today, there are over 400 species of ungulates on Earth, with billions of living individuals. But here we see that, minimally, there were 750 ungulate species in South America alone and probably thousands of species. In a young-earth creationist’s model, almost all of these species would have had to have been living at one time. This is very difficult to understand from an ecological perspective. How could this many species live side by side, competing for the same resources?
In an evolutionary model, or even progressive creation (Reasons to Believe model), South America probably only had 25 to 100 species living at any one time, with some going extinct and new species being formed over time. There are around 130 species of Ungulates living in Africa today but even there fossil species outnumber modern species. North America also has far more fossil ungulate species than living species.
The pictures that emerges from the fossil record, all of which is found in just the very top layers of rock and sediment on Earth is one of tremendous past diversity of ungulates. Thousands upon thousands of species of ungulates have walked this Earth but for the past several thousand years there have only been about 400 living species.
As I said before, we can marvel at the diversity we see today but that diversity pales in comparison to that present over past eons. the diversity of life is so great that earth of only 6000 years of history would seem utterly incapable of providing a home for all those organisms and their needs.
This is an edited and updated version of an article originally posted January of 2015
Good article. One quibble though. The terror birds weren’t the only large predators. The sparassodonts, such as thylacosmilus, also were present. I have to think there were others that are just not known. I find it hard to imagine an ecology so depauperate in large predators. Just my speculation though.
There were also some terrestrial crocs, like the sebicids, at least early on. Not sure how long after the continental split they lasted though.
Thanks so much for the info. I was wondering about. Given the anatomy of many of these ungulates and the reconstructions even considering some artistic liberties it looks like many of these animals did have adaptions for escaping predators and/or protecting themselves. I suppose some of those characteristics may be due to mating competition but surely not all. Makes sense there would more predators that we recognize today. I believe the suggestion that they weren’t well equipped for these new predators would still stand. I’ll make some changes to the text this evening to reflect this.
Nice article — but please note that there were indeed mammalian predators in South America prior to the Great American Biotic Interchange —- an entire order of carnivorous marsupials, known as the borhyaenoids (or sparassodontids). Most of these were extinct before the interchange, as were most of the native ungulates —- so competition with invading ungulates seems rather unlikely.
Also note that the Plio-Pleistocene fossil record of South America records a rather large diversity of unique types of horses and also of gomphotheres (a now extinct family of probscideans), representing diversification of these lineages following their immigration to the continent. All of these were extinct by the end of the Pleistocene
Thanks for the corrections. Just a moment before your comment the same things was pointed out to me. I totally missed the sparassodontids which is embarrassing since I had read about them no less than year ago. I will definitely update this and include these. BTW, do you think my 750 extinct species is a realistic understimate of species of SA ungulates. Seems like it would be a huge underestimate but I don’t know anything about the perceived completeness of the fossil record in that part of the world.
YECs eg Andrew Snelling appear to assume that during ‘Noah’s Flood’ (not afterwards) a single continent broke apart and ‘catastrophic plate tectonics’ rapidly moved eg the South American continent to its present position.
“Remarkably, all of these ungulates have only ever been found preserved in South America.” YECs are probably disappointed that there is not a verse in Genesis 8 or Genesis 9 implying that God wanted some specific ‘kinds’ of animals to repopulate specific continents on Earth and to multiply in number there but not elsewhere. (In fact these chapters to me imply that the writer thought that the flightless animals disembarking from the ark could easily and quickly repopulate the Earth – suggesting that the writer – despite perhaps being aware of coastlines – thought that there was, less than 5,000 years ago, one single interconnected landmass on the planet. Which of course there certainly was not even during any imaginary subsequent glaciations with their reduced sea levels and/or ice ‘bridges’ near the poles.)
Sounds scary when you think about how most of Earth’s species are dead.
The next time I talk to a YEC, and they ask me why I have a problem with their view of creation, I’m just going to say, “Well, honestly, I just can’t get around the ungulate problem.”
LikeLiked by 3 people