Book 7

Chapter 7 How Life on Earth Has Changed Thru Time

The purpose of this chapter is to take a brief look at the reality of the fossil evidence for life’s changing nature and development through the vast periods of geologic time. Geologic time is being defined on a continually refined and up dated scale. The broad outline does not change but where precise lines are drawn between the individual time periods does. The time charts given here are rounded to make them more easily understood but this does not alter their essential validity. Below is a reference chart for geologic time to give a general overall perspective.

The Major Changes in Life Thru Geologic Time

The oldest fossil evidence of life on earth is 3.5 billion old fossil bacteria. In some of the oldest sedimentary strata are found stromatolite structures of contorted and finely laminated layers of calcium carbonate that were deposited by cyanobacteria. These stromatolite structures are found in extremely ancient strata as well as in geologic strata deposited ever since. They continue to be produced even today by living cyanobacteria. During the time period between 3.5 billion years ago and 550 million years ago many fossils of microorganisms like cyanobacteria, algae, and protozoans are found as fossils. These types of living organisms continue to live today.

Toward the end of the Proterozoic time period, about 90 million years or so before the beginning of the Cambrian period (which occurred about 540 mya) a group of completely new simple multi-celled animals begin to show up in the fossil record. These have been given the collective name of the Ediacara fauna. Currently they have no known antecedents, nor did they seem to leave any descendants. They remain a considerable mystery. They do not provide the antecedents for the “explosion” (A very slow one!) of life forms at the beginning of the Cambrian. They were first discovered in Australia (Glaessner, 1984) and have since been found in Russia, Europe, Newfoundland, and SW Africa.

Near the beginning of the Cambrian period an entirely new group of somewhat bizarre animals were found in the Canadian Burgess Shale near the small town of Field, British Columbia (Gould, 1989). These too are mostly without known antecedents, but, unlike the Ediacara fauna, many seem to have left descendants of similar form. Among those descendants are the trilobites. Trilobites are perhaps the most familiar ancient fossil to many people as they are the “poster child” fossil for the Cambrian. They occur very early, exhibit many diverse forms, then go extinct about 250 million years ago. Fossils similar to those of the Burgess Shale are also found half a world away in Chengjiang, China (Hou et al., 2007).

The strange lack of ancestors for the Ediacara, Burgess Shale, and Chengjiang faunas prompts Andrew Knoll, Harvard professor and paleontologist, to make the following statement.

Our peregrinations have, in fact, revealed the essential truth of Cambrian evolution: life has deep Precambrian roots, but the complex forms of Cambrian animals do not. There is nothing like the Cambrian until the Cambrian.

The Cambrian Explosion is the culmination of Precambrian evolution but a departure from it, as well. Can we build an understanding that captures both the continuity and revolution of Cambrian biology? (Knoll, 2003:179-180).

From the Cambrian time period (about 550 mya) onward life forms take on a much more familiar appearance. Bacteria, fungi, plants, insects, mollusks, worms, and other invertebrates – each has its own life history story to tell during this time, but we can’t possibly examine all those stories here. We will examine the general development of some major vertebrate groups through time then concentrate on four specific vertebrate fossil lines to illustrate the substantial changes that have occurred in animals over time. These animals were not just all at once created in their modern form.

First, however, a brief interlude… The living fossils

But before we leave the other life forms to concentrate on how much the vertebrates have changed, we should mention the “Living Fossils.” Contrary to the way most fossil animal lines change through time, some life forms have remained remarkably stable for multiple millions of years. These are, however, the exceptions, not the rule. But they do provide an important observation and question about DNA stability and what makes it change.

Living fossils include common animals such as dragonflies, cockroaches, frogs, bats, shrimp, horseshoe crabs, coelacanths, and scorpions. A very notable living fossil is the brachiopod Lingula. Species of the same genus are found in Ordovican strata, ca. 460 million years old.

Fossil dragonflies are found in strata older than 250 million years. Horseshoe crabs, shrimp, and modern looking frogs in 180 million year old strata of the Jurassic. Bats, looking like modern forms occur in the 45 million year old strata of the Green River formation.

Living coelacanth fish, last found as fossils in strata of dinosaur age, were found swimming off the coast of East Africa in the 1930’s and are still alive today.

There are many more “younger” examples of ants, termites, and other animals found in amber that lack any significant appearance of change over many millions of years. How much animals change over time is quite variable. Determining the cause of this change is a topic worth exploring.

To see how some animals have made substantial change through time we will use four groups of vertebrate animal to show in what ways and how much they have changed through millions of years. In chapter 9 we will examine how the human-like hominins have changed through the last few million years that their fossils have been found.

A brief overview of the major vertebrate history.

The beginning of fish… Ordovician (ca. 450 mya)

The fossil history of the vertebrates primarily starts with fish. The earliest fish are “fish shaped” but without fins, scales, internal skeleton, or jaws. They were covered with a boney armor and sucked food in through a jawless mouth. As time passes we begin to find forms with fins, internal skeletons, jaws and more typical fish structures. There are many different forms and changing designs of these fish that occur over many millions of years. Their complex history is not done justice by a brief summary. There are myriads of forms of these early fish. The figure below only gives a mere indication of a few types.

After this starting place we move up through the fossil record to find sharks, rays, lungfish, and lobe finned fish. After 250 million years ago we begin to find fossils of fish of essentially modern design, some of which have living types today. Some of their groups continue to live today. The most common modern fish begin to be found as fossils about 65 million years ago.

A good, visual summary of the complex history of fish can be found in references like Long, 1995 but is much too complex to illustrate here and do the realities justice.

The introduction of amphibians… Fish are given legs.   Late Devonian (ca. 365 mya)

In the Upper Devonian (about 375 mya) in North America and Europe lived the fish Eusthenopteron. Adults of this fish reach nearly 6 feet long and are found in abundance near the east coast of Canada. It is very clearly a fish but has characteristic skull bones and bones in lobed fins that are very similar to some of the earliest known amphibians such as Ichthyostega and Acanthostega. It also shares many skull and lobe fin features with the transitional fish/amphibian forms, Tiktaalik and Panderichthys. An excellent visual presentation of these features can be found in Carroll, 2009:35-44. Clack, 2012 is also a good source for this period and development. Shubin, 2008 is a good read on the discovery of Tiktaalik. It is during this time period that some fish were given legs and became amphibians about 375 mya.

Beginnings of reptiles… Carboniferous (ca. 300 mya)

Fossils that have been traditionally called “reptiles” are a very diverse group. They are more modernly included within an even larger group termed “amniotes” because of their relationship to the amniote egg. The amniote grouping also includes modern turtles, snakes, crocodiles, birds, and mammals. So this large group obviously needs to be dealt with as separate subgroups with individual and in most cases, unrecognizable names. The reasons for this are beyond what we want to deal with in this brief survey.

The amniotes first show up in the fossil record in the Early Pennsylvanian (ca. 310 mya) superficially looking much like some amphibians. Their history is complex. Even major fossil groups of these animals would be unknown by the typical person. We will try to make sense of that history by talking of the first appearance of familiar modern groups. The turtles first show up as fossils in the Late Triassic about 238 mya.   Snakes in the Early Cretaceous about 135 mya.   Crocodiles in the late Triassic about 235 mya. Dinosaurs in the Late Triassic about 230 mya. (Data from Benton, 2015).

Dinosaur times…

The dinosaurs (‘fearfully great lizards,’ (Benton 2015:205)) are a rather diverse group. Some were land animals, some swam in the oceans, and others flew in the air. They dominated the land from the Triassic to the end of the Cretaceous for about 180 million years before being replaced by mammals 65mya. Since these are some of the most commonly known fossil vertebrates to most people there seems little need to go into great detail of them. For our purpose it seems adequate to show when they lived and when they died in terms of geologic time.

The introduction of birds…

Reptile type animals were given feathers, pneumatic bones, endothermy, and taught to fly.

Birds are the most successful terrestrial vertebrate, abundant in both numbers of species and populations. About 300 billion birds, with 10,000 species, now inhabit the Earth, as compared to 3,000 species of amphibians, 6,000 species of reptiles, and perhaps 4,500 species of mammals. (Chatterjee, 2015: preface).

Birds are perhaps only outnumbered in modern vertebrates by the number of species of fish. There are reportedly over 20,000 species of living teleost fish.

The earliest geologic time period in which birds are found in the fossil record depends upon what one calls a definite bird. It would be 225 mya if Protoavis from Texas (Chatterjee, 2015) is considered a bird. About 160 mya if Archaeopteryx is really to be considered a bird rather than a dinosaur with feathers, which some serious paleontologists now conclude. However, by about 125 mya there are many good fossils of undisputed birds. The other details need not concern us here. Birds shared the earth for millions of years with the dinosaurs. That is an important conclusion about birds from the fossil record for us to consider at this point.

The introduction and continuing dominance of mammals…

For the last 65 million years, after the demise of dinosaurs, the land has primarily been dominated by mammals. But mammals did not originate 65 mya. Mammals are an old group of vertebrates that have been around for about 200 million years, nearly as old as the dinosaurs.

Modern mammals are identified by their hairy body and mammary glands by which they suckle their young.   These two features seldom work to identify fossil mammals. We need to look at the differences between reptiles and mammals in their skeletal features.

Three simple things we may consider. First is the joint between the skull and the last vertebrae. Reptiles have a single ball joint (condyle) on the back of their skull, while mammals have a double condyle joint. The second is the nature of the lower jaw bone. Mammals have a lower jaw bone that is made up of a single bone, the dentary. Reptiles have jaws made up of multiple bones.

Third, reptiles generally have homodont teeth, that is, all their teeth have essentially the same structure and use. Mammals, on the other hand, generally have heterodont teeth… Teeth which differ in structure and use. Consider our teeth as a human mammal. We have four different types of teeth: incisors, canines, premolars, and molars. Other mammals are similar and thus are quite different from the uniform teeth of reptiles.

One of the reasons birds have been thought derived from reptiles is because they share a single condyle attachment of the head to the vertebrae. Another is that some birds have multi-boned lower jaws like reptiles. In addition, some fossil dinosaurs have been found to have had feathers.

Remarkable Design Transitions in the Vertebrates

1. Fish are given legs

2. The invention of the remarkable amniote egg – Allowing an embryo to develop on dry land in a self contained capsule, complete with mechanical protection, liquid bath, air respiration, food pantry, and septic tank for refuse disposal. …All under the direction of the DNA in the mother’s egg!!!

3. Origin of birds - A reptile is given feathers, wings, endothermy, and taught how to fly.

4. Changing the DNA so that the extra reptile lower jaw bones are repurposed as mammal ear bones.

5. The human brain and spirit... exceeds comprehension!

The Mammal-Dinosaur Transition at the start of the Cenozoic did not begin with the present common modern mammals… A sampling of a few large bizarre early Cenozoic mammals that are now long since extinct will illustrate the difference. Many more examples could be given.

The Unitatheres
Large rhino sized animals, but not rhinos. The left picture is of a diorama in the Utah Natural History Museum at Vernal, UT. The skull is at right.

The Titanotheres

Another large rhino like mammal that lived in the early Cenozoic. Following is the skull of one of these animals found in Death Valley National Park. Titanotheres are found across much of the Western U.S.

The Chalicotheres

Another strange group of large mammals that lived in the mid Cenozoic of North America were the chalicotheres. In many ways they superficially resembled a large horse but with claws on their feet instead of hooves.

Many of the mammals that lived in the time period soon after the dinosaurs were totally different than those alive today. These three exotic types are given as examples. There are many others. They illustrate that the change from dinosaur dominance to mammal dominance was not a quick switch to the mammal world of today. There was a long slow transition within the mammal group.

Many of the types of mammals that are still alive today have gone through rather extensive changes through their extensive existence on earth. To illustrate these changes we will examine four groups of common mammals alive today.

An Instructive Look at the Life Histories of Four Common Living Mammal Groups: Horses, Camels, Elephants, and Whales

The Horses
The evolution of the horse is the classic story of animal evolution. It is one of the first known and best documented of the evolutionary lines. Its development spans a time period of over 50 million years. Below is a chart that illustrates when various genera of fossil horses lived in prehistoric time. Note that the chart covers only the last major geologic time period, the Cenozoic with its subdivisions. It is during this time period that all horse fossils are found. For this reason, and to simplify and correlate the understanding of these different lines, the same chart and chronological framework is used for all four lines.

The reader is referred to chapter 6 for questions concerning the validity of the known geologic record and time scale.

Only the more common genera of fossil horses are indicated on the chart. The chart is true, but it is a simplified picture of the horse’s history. It is by no means exhaustive. (For more detailed information on horse development see: Osborn 1918, Matthews 1926, Stirton 1940, Simpson1951, McFadden 1992, Franzen 2010.) This chart’s purpose is to show the diversity and general development of horses through geologic time. This has occurred primarily in North America. The timing and sequence of these genera show the reality of the horse’s developmental history. The following illustrations and graphics will give a general visual picture of how some of these genera differed from one another and changed through time.

The heavy dark lines indicate the approximate geologic time span during which the horse genus is found in the fossil record. Even though the most complete record of horse evolution is found in North America, the horses became extinct in North America in pre-Columbian times. The living horses in North America today have all been reintroduced during the European settlement times.

The earliest “horses” found in the geologic record are of the genus Hyracotherium, which is popularly known as “eohippus.” One would not even think of it as a horse since the species of this genus are generally the size of a large house cat. The English anatomist who first described the fossil thought it looked like a hyrax (The biblical “coney”). Hence, he gave it the name, Hyracotherium, or hyrax-like animal. A little later this horse was described in North America and named Eohippus because there it was correctly associated with later fossils in the horse line. It is primarily because it can be traced through the development process to later fossil horses that we can conclude that it is, indeed, an early horse. Being first, the name Hyracotherium had precedence over Eohippus, which is a bit unfortunate.

By analogy, we would not automatically conclude that Henry Ford’s first motorized vehicle was the precursor to the latest models of Ford automobiles without knowledge of the intervening design steps in the developmental process. The modern Ford’s design was not in Henry Ford’s mind when he started the process. The modern cars were creatively developed to their current design over many years and through multifaceted processes. If we accept the presence of a supernatural intelligence, I think it is reasonable to consider that the development of the horse (and other animal lines) followed a similar pattern. As with the Ford automobile lines, there are likewise a number of dead end “Edsel” and “Pinto” horse genera in the line as well. In fact, given enough time nearly all automobile lines go extinct. Witness the recent demise of Oldsmobile and Pontiac automobile lines in the United States. Consider the number of horse genera that have lived in the past. Yet, today only one genera of horse, Equus, continues to exist.

Major changes in the horse line through time can be briefly examined by considering changes in size, tooth structure, and foot structure. Certainly many other changes occurred in the process but these three are the most obvious and will be sufficient to show the basics of their change or evolution. One cannot fully appreciate the changes and differences without examining the actual tooth and skeletal material of the sequential forms rather than just these few graphics.

Changes in Horse Size

The size of horses greatly increased through time. Hyracotherium was small. It ranged in size from about 10 to 20 inches high at the shoulders. The average height of Mesohippus was about 24 inches. Parahippus and Merychippus would seem to be in the range of 40 inches high while the modern horse is more like 60 inches on the average. Modern ponies and miniature horses might seem to complicate this general height range. These, however, are merely modern forms of Equus that have tooth and foot bone structures that are of the same design and construction as a modern, full-sized horse.

Hyracotherium (Eohippus) Generally considered the first in the horse line. Formerly known as Eohippus. There are earlier fossil forms but clear definition has proven controversial.

Mesohippus
A fairly common fossil horse found in many areas of North America. It had three toes on both front and rear feet. A feature common in most fossil horses. Fairly small and gracile in form.

Parahippus
A larger horse with larger teeth which were similar in design to those of Mesohippus. It had three toes on each foot.

Merychippus
A larger horse with completely remodeled cheek teeth. This new design of tooth occurs in nearly all following genera of horses. It still had three toes on each foot.

Equus
The modern horse. Generally much bigger but comes in a wide variety of sizes, all of which have similar skeletal design features... Such as similar tooth design and single toed feet.

Changes in Horse Foot Structure

The feet in the horse line likewise change dramatically. Hyracotherium has four toes on the front feet and three on the rear. Mesohippus has three toes on both front and rear feet, as do most of the later genera listed on the accompanying chart except Equus, Dinohippus, and Pliohippus. The drawings below illustrate these changes in the front feet of the horses.

A sequence of the structure and relative size of the front feet of horses from Hyracotherium, Mesohippus, Parahippus, Merychippus, and Equus. Hyracotherium had four toes on the front feet and three on the rear. The now extinct Hipparion Group continued the three-toed condition throughout their existence. Below are the actual fossil foot bones of Parahippus (top) and a small Equus (bottom). A U.S. penny gives relative size.

Changes in Horse Tooth Structure
Some of the most obvious and significant structural changes in the horse genera occur in the feet and of the teeth through time. We will now consider the changes in the teeth.

The crown height of the teeth of Hyracotherium were very small, about 1/8 to 3/16ths of an inch high. At the other extreme, some modern Equus tooth crowns are 4 inches or more high, and of a completely differently design. This is one of the fascinating stories in the development of the horse.

The biting (occlusal) surface of the cheek teeth crowns are somewhat similar in Hyracotherium and Mesohippus. This difference is best shown rather than explained. Below is a picture of upper right cheek teeth of Hyracotherium and Mesohippus. The picture below it illustrates how each cone and ridge (loph) of the crown has a name. For simplicity we will try to use as few of these terms as possible. Hopefully the picture will replace a thousand words.

The similarities of the teeth of the two different genera are clearly seen. Differences will also be noticed. The molar of Mesohippus is bigger and its cones and lophs are more clearly defined. However, if we were to compare the teeth with different mammals we would see more dramatic differences. That’s significant in realizing they are in the same “line” of mammal. The changes in tooth features can be easily be followed in much of the horse line.

Hyracotherium Mesohippus

As we will see these prominent features of the upper molar teeth can be followed from Hyracotherium to Equus.

The design of the tooth crown of Hyracotherium, Mesohippus, Parahippus, and Hypohippus remain basically the same even though the height and width of the tooth increases rather dramatically. These teeth were emplaced in the gum in their final form, much like human teeth are emplaced. Such a tooth is called low-crowned or brachydont. Once the brachydont tooth is worn down to the gum it is completely worn out. This is unlike later horses which had high-crowned or hypsodont teeth. The hypsodont teeth of later horses continue to emerge from the gum line throughout the life of the horse.

Change in tooth size compared: Hyracotherium, Mesohippus, Parahippus, and Hypohippus. Note that the basic structure of the teeth remains essentially the same even though there is considerable increase in size. Consider the time difference of when these horse genera lived from the chart.

The major tooth change beginning with Merychippus

A completely new design of tooth is introduced with the genus Merychippus. Over time the tooth crown in the earlier horses became higher and higher. This increase in height is clearly shown in the pictures previously shown. The troughs between the cones and ridges became deeper and deeper. The enamel had less lateral support. It could be more easily broken. Chewed food could be wedged into the deep troughs or fossa of the teeth.

The new tooth design is quite different. It was much higher crowned but of a stronger structure. The deep troughs are filled in with a new material called cementum. This material also coats the enamel on the outside surface of the tooth as well, greatly supporting the thin brittle enamel. The crown height could now be increased even more. Such a tooth had a tremendous grinding surface with great depth. At the same time the tooth no longer erupted all at once from the gums. It rather erupted over time so the tooth could continually erupt as it wore down. This was a considerable innovative change in making the tooth an effective grinding mechanism. Modern Equus teeth, uppers and lowers, can reach a height of four inches or more.

This tooth innovation occurs in nearly all of the later horses except the Hypohippus line. The teeth could not just be made bigger, they had to be of a different design to be effective. Of course such changes also required changes in the jaw and skull structure of the animal, as well as the eruption mechanism.

This new horse tooth has a surface somewhat like a modern grinding wheel in which hard corundum or diamond crystal is embedded in a softer matrix. This greatly increases the durability and wear characteristics of the tooth, giving it a much more effective and lasting grinding and shearing surface. In addition the height of the crown was greatly increased. Unlike the old brachydont tooth this new tooth continued to erupt through the gum line throughout the horse’s lifetime. This new style of tooth continues in most of the later horses (Equus, Dinohippus, Pliohippus, Calippus, Nannippus, and the Hipparion Group of genera). Hypohippus continued with the old design of tooth. There was also a genus not listed on the chart called Megahippus of the middle Miocene that had an even larger tooth of this old design. Of course the jaw and skull design also had to change substantially to accommodate this new style of tooth.

A comparison of the change in crown height through time is shown below.

Changes in cheek tooth crown height from Hyracotherium to Equus. The crown height of Hyracotherium and Mesohippus were so low it was difficult to stand them on edge for this picture.

Even in the crown of a modern Equus the features of the basic Mesohippus tooth structure can be identified.

The occlusal surface of an Equus tooth showing how the cones and lophs relate to those of Mesohippus shown above. Since this is a heavily abraded surface the cone peaks have been worn off as have the enamel ridges of the lophs. The new material cementum has been added outside the enamel to strengthen the tooth. It makes the cones and lophs a bit harder to distinguish.

The horse line went through many changes over a period of about 50 million years. This brief explanation should be adequate to give a reasonable understanding of the major changes involved. The actual fossil material illustrated should help verify that such changes really did occur in the history of the horse. A biblically oriented faith must incorporate such knowledge into its understanding of the past history of the earth and life upon it.

How many or which of these changes were brought about by natural selection and which were brought about by intelligent manipulation is probably impossible to determine with confidence. This author, finds it incredulous to believe that all these changes were purely the result of unguided natural processes at work.

The Camels

Camels have a 30+ million year fossil history. Most of that history is found in North America. Only in comparatively recent geologic time have camels made their way into Asia, the Middle East, and North Africa where we think of them today. Modern living camels include the two-humped Bactrian camel of Asia and the one-humped dromedary of the Middle East and North Africa. They are often both included in the single genus Camelus. Earlier in geologic time camels made their way from North America into South America and survive there today as the genus Lama, into which the llamas, alpacas, guanacos, and sometimes vicunas are placed. Some authors place vicunas in a separate genus, Vicugna.

The chart below shows the camel genera in relation to when they are found as fossils in the geologic strata of the Cenozoic time period. This is the same graphic framework that was used for the horses.

The chart represents where some of the more important genera of fossil camels are found within the geologic record. While it is a true picture it is by no means comprehensive or complete. The purpose here is to paint a general history of the camels to give the understanding that a wide variety of camels have lived throughout the geologic past. Only two genera are alive today.

Unlike the horses the cheek tooth form remains remarkably similar over a vast time period. The tooth crowns may get a little higher in some forms than others but the basic tooth form is quite consistent. This is illustrated below where the cheek teeth of Poebrotherium (Bottom) are compared with a modern Lama (Top). This is stability of tooth form is certainly different from the substantial tooth change of the horses and elephants through time. It shows the lack of major difference in tooth structure over approximately 30 million of years in the camels.

All camels, even Poebrotherium and the vicuna, have only two toes on each foot. This hasn’t changed over time as have the foot structure of the horses. The two metapodials, the foot bones with which the toes articulate, are separate in Poebrotherium, but are solidly fused together in later genera. Despite the similarities that clearly bind them together as camels, the different genera exhibit some rather dramatic differences in size and appearance throughout geologic time. These differences are clearly shown in the later graphics.

The fused metapodial of a Late Cenozoic fossil camel. In Poebrotherium this bone was two separate bones. In all later fossil and living camels it is fused into a single bone. The metapodial is the foot bone that articulates with the two toes of the camels.

Below: the foot and toe bones of a Bactrian camel from the Field Museum, Chicago.

Below are two mandibles from different genera of modern camels. The bottom mandible is of the genus, Camelus. The top is of the genus, Lama. Note that the size is considerably different but the structure of the teeth and jaw is very much the same. These features together with their similar two toed foot bones make it easy to see why they are both considered to be camels.

Below is an illustration of Poebrotherium which lived in the Oligocene, some 30 million years ago. Skeletons of this little camel are found in many museums across the United States. It stood about three feet high.

Poebrotherium

Next is an illustration of Stenomylus. It lived five to ten million years later than Poebrotherium but was even smaller in size, standing only about two feet high at maturity. It was lightly built, like a small antelope, but its tooth and skeletal structure was that of a camel, not an antelope.

Stenomylus

Below is Oxydactylus. It lived at the same time as Stenomylus but was much larger and more heavily built.

Oxydactylus

Titanotylopus

The extinct giant among the camel family, Titanotylopus. Some individuals reached nearly 11 and a half feet above the ground and were massively built. Below is the actual mounted skeleton of a similar giant camel in the Nebraska State Museum in Lincoln, NB. Compare the size of the camel with the workman in the lower left corner of the picture. Such giant camels are extinct today.

The genus Camelops was a common camel in the western United States in late geologic time. Its fossils are often found along with horses and mammoths in very late deposits. It is estimated to have died out about 10,000 years ago (Anderson 1984:71). It is quite similar to the living camels (Camelus) but 20% or so larger.

Camelops

The genus Camelus, one of the two (or three by some authors) living genera of camels.

Camelus

In many ways the differences between the genera in the camel group through time seem rather limited in relation to the changes seen in the horses and we will see later in elephants. Their tooth and foot design stayed remarkably similar throughout their history. Size was their big difference. The important point to make is that camels are another group that has been around for multiple millions of years. During that time they changed enough to be grouped into discrete genera that shared common characteristics within the group in addition to the common characteristics shared by all other “camels.”

The Proboscidea

The elephant-like animals are another interesting group of mammals that show substantial variety and change, especially in their skulls, teeth, and tusks through time. Consider the history outlined in the chart below. They occupy a time frame very similar to the camels.

The earliest obvious “elephant” in the line is Palaeomastodon from North Africa. The only two living genera of elephants are Elephas, the Asian elephant, and Loxodonta, the African elephant. The time in between the beginning and end of the line is filled with an unbelievable variety of elephant forms, most will not even be mentioned here. (For more detailed information on elephant development see….Osborn 1936 & 1942. Maglio 1973, Shoshani and Tassy 1996, Lambert and Shoshani 1998.)

It is nearly impossible to present a reasonably complete picture of the history of the elephants. At best there are more holes in the picture of their history than in that of the horses. The important thing to realize is that there were many different types of elephants living over many millions of years. Many of these were very different from one another, especially in skull, teeth, and tusks.

If Deinotherium is used as an example we find a head scratching situation. In form and size it is much like an elephant. It lived for a long, long time with really very little change in its basic form, from the early Miocene until the times of the hominins. Its general form stayed very similar throughout that time span, unlike many other members of the elephant group. But it was very different in tooth and tusk than the rest of the elephants. Deinotherium only had two tusks but they were both on the bottom jaw. Instead of curving upward, forward, and/or outward like most other elephants, they curved down and backward like a rake. Their teeth were significantly different as well. These differences we will see as we proceed.

Much of the history of change in the elephants can be followed in the changes in the head, teeth, and tusks. These varied dramatically through time. The history of the elephants is far more complex and difficult to understand than that of the horses and camels. Two leading students of the group summed up their feelings with this statement:

“…the complexity among proboscidean taxa, and especially among gomphothere lineages, is becoming more and more perplexing as we study them in greater depth.” (Shoshani and Tassy 1996:348)

Let’s take a look at some of the key genera that have lived throughout their history. The chart on the previous page is based on the same time frame as were the charts of the horses and the camels. This late Cenozoic time period witnessed much change and evolution in nearly all mammal lines. The four lines that we are examining are only a sampling of what was happening. Now for a look at the elephant-like animals, the proboscideans.

Palaeomastodon

Often grouped with the Gomphotheres, Palaeomastodon is one of the earliest of the fossil elephants that looks like an elephant. This model of the skull is in the Prague Museum of Natural History. Note that it has tusks on both the upper and lower jaws. This is not uncommon for many of the Gomphotheres.

Mammuthus columbi... a true giant of the group!

Mammuthus columbi Univ. of Nebraska State Museum, Lincoln

The teeth of the mammoths (Mammuthus). On the left is the tooth of a wooly mammoth from NW Europe. On the right is a Columbian mammoth tooth with a few of its plates missing. Both teeth are essentially of the same design… Plates of enamel and dentine overlain with cementum.

Mammut (Mastodon)

American mastodon Univ. of Nebraska State Museum. They have two tusks on the upper jaw.

Two typical Mastodon teeth.

Stegodon

A proboscidean that lived in Southeast Asia. Once thought to be the evolutionary step toward the stacked plate teeth of the mammoths, but was found to have lived much later than the early mammoths so that could not be true.

Stegodon teeth.

These teeth are very low crowned but otherwise of somewhat similar design to the mammoths and modern elephants.

The Gomphothere Group
This is a large and varied group of proboscideans that lived for a long time. They are now all extinct. Their teeth are typically called bunodont and the molars can be exceptionally long. They often have tusks in both upper and lower jaws, like Paleomastodon. Sometimes the tusks are rounded and flattened and some are wide and flattened in the “shovel tuskers.”

A few typical Gomphothere teeth. Take note of how different they are than the previous proboscideans.

Eubelodon A gomphothere. Univ. of Nebraska State Museum Tusks in upper and lower jaws.

Stegomastodon, another gomphothere. Univ. of Nebraska State Museum collection. Note it only has tusks in the upper jaw. Univ. of Nebraska State Museum

Stegomastodon tooth

AmebelodonLower jaw from a uniquely different member of the Gomphothere Group. Univ. of Nebraska State Museum One of the so called: “shovel-tuskers.”

Platybelodon Lower jaw from another of the uniquely different member of the Gomphothere Group, the “shovel tuskers.” Univ. of Nebraska State Museum

The Deinotheres
A truly strange proboscidean group. They have been uniquely different from their first appearance until they went extinct not very long ago. Their fossils occur with some of the hominins. They are unknown in the New World but were wide spread in the Old World, especially Europe and Africa.

Deinotherium skull. Prague Natural History Museum

Examples of Deinotherium teeth. Note the extreme difference from those of the any other “elephant” teeth.

Deinotherium graphic in the Prague Natural History Museum.

The proboscideans are a complex group that have varied in many different ways throughout the last 30 million years. Only two genera are alive today. In contrast, a recent estimate of fossil genera was 162 (Shoshani and Tassy 1996:336). There seems to be only moderate consensus on how the fossil lines can be interrelated. Apparently the proboscideans have a much more complicated history than the horses and camels but they coexisted with them throughout the same time period.

The Whales

For years creationists have used whales as a poster child for the lack of fossil evidence for their being changed from land animals to marine animals through time. Recent fossil evidence has changed all that. In the past 30 years much of whale fossil history has been uncovered.

This is summarized by Gingerich…

Whales are as interesting an example of evolution, evolutionary transition, and evolutionary transformation through time as anyone could hope to find in the fossil record. Fossils document important intermediate stages in this history, but there will always be room for more intermediates in the future. New archaic whales are being found in Africa, Antarctica, Asia, greater Australia, Europe, North America, and South America, by investigators young and old. Thus a fine fossil record is becoming even better. There is opportunity too beyond field exploration and discovery. Interpretation of form in terms of function is still in its infancy for early cetaceans. If form and time are keys to understanding Whale evolution in terms of history, then form, function, and time together are keys to understanding whale evolution in terms of adaptation. (Gingerich 2015:252-253)

Whale history throughout the Cenozoic

The author has not spent the extensive time on whale fossil history as he has on the horses, camels and elephants. They are added here because of the abuse of the fossil record by many creationists. Their fossil record seems as well verified as the other three mammal groups we examined in more detail. One would be foolish to disregard that record as nonexistent.

Certainly this chart lacks the detail of the other mammal charts previously shown. But it does give a general time sense of when the fossil whale groups are found in the record in comparison to the horses, camels, and elephants.

As with the other mammal records, a sequential record of changing fossil forms shows that these forms actually existed in the time frame suggested, but it does not prove what caused the change and development. As previously stated, faith is still the basis for believing what caused the changes, for the theist and the atheist alike.

Chapter Summary

The animal life on earth has changed dramatically as we move through geologic time. Many are radically different than forms living today. On the other hand there are the living fossils that seem to have changed very little since they are first found in the fossil record. Many millions of species have gone extinct over time. There are hundreds of lines or families of similar animals, seemingly developed from one another. Other life forms show up and disappear with no trace of ancestor or descendent.

These are the facts from the fossils. How one interprets these facts depends upon one’s basic faith. If one’s faith is that of materialism then one attributes all these introductions of life forms and their development to natural processes no matter how illogical the process seems to be. If one is a theist, one can easily attribute these observed changes to intelligent manipulation in addition to the natural processes that may be scientifically shown to occur.

But there is no doubt about it, how one interprets what was happening during the time the fossil record was being formed is based on faith.

References for Chapter 7

Benton, Michael J.
2015 Vertebrate Paleontology, 4th ed. Wiley Blackwell.

Berta, Annalisa
2017 The Rise of Marine Mammals. Johns Hopkins University Press, Baltimore.
Berta, Annalisa, James L. Sumich, and Kit M. Kovacs
2015 Marine Mammals Evolutionary Biology, 3rd ed. Academic Press (Elsevier).

Chatterjee, Sankar
2015 The Rise of Birds, 2nd ed. Johns Hopkins University Press, Baltimore.

Carroll, Robert L.
1988 Vertebrate Paleontology and Evolution. W. H. Freeman and Co., New York.
2009 The Rise of Amphibians. The Johns Hopkins University Press, Baltimore.

Clack, Jennifer A.
2012 Gaining Ground, 2nd ed. Indiana University Press, Indianapolis.

Franzen, Jens Lorenz
2010 The Rise of Horses. The Johns Hopkins Univ. Press, Baltimore.

Gingerich, Philip D.
2015 Evolution of Whales from Land to Sea. In Great Transformations in Vertebrate Evolution, edited by Kenneth P. Dial, Neil Shubin, and Elizabeth L. Brainerd, pp. 239-256. University of Chicago Press.

Glaessner, Martin F.
1984 The Dawn of Animal Life. Cambridge University Press.

Gould, Stephen Jay
1989 Wonderful Life. W. W. Norton and Co., New York.

Hou Xian-Guang, Richard J. Aldridge, Jan Bergstrom, David J Siveter, Derek J. Siveter, Feng Xiang-Hong
2007 The Cambrian Fossils of Chengjiang, China. Blackwell Publishing.

Knoll, Andrew H.
2003 Life on a Young Planet. Princeton University Press.

Lambert, W. D., and J. Shoshani
1998 Proboscidea. In Evolution of Tertiary Mammals of North America, edited by C. M. Janis, K. M. Scott, and L. L. Jacobs, pp. 606-621. Cambridge Univ. Press, U.K.

Long, John A.
1995 The Rise of Fishes. The Johns Hopkins University Press, Baltimore.

MacFadden, Bruce J.
1992 Fossil Horses. Cambridge University Press.

Matthew, W. D.
1926 The Evolution of the Horse. Quar. Rev. Biol., Vol. 1, No, 2.

Marx, Felix G., Olivier Lambert, and Mark D. Uhen
2016 Cetacean Paleobiology. John Wiley & Sons, Ltd.

Osborn, H. F.
1942 Proboscidea. Vol. II, The American Museum Press, New York, NY.
1936 Proboscidea. Vol. I, The American Museum Press, New York, NY.
1918 Equidae of the Oligocene, Miocene, and Pliocene of North America. Memoirs of the Amer. Muse. Of Nat. Hist., New Series, Vol. II, Part I.

Shubin, Neil
2008 Your Inner Fish. Pantheon Books, New York.

Simpson, George Gaylord
1951 Horses. Oxford University Press, New York.

Stirton, R. A.
1940 Phylogeny of North American Equidae. Bull. Dept. of Geol. Sci., Vol. 25, No. 4, pp.165-198.

Thewissen, J. G. M., editor
1998 The Emergence of Whales. Plenum Press, New York.
2014 The Walking Whales. University of California Press.