BEASTS OF EDEN
Creationists seem to think that some scientists have looked at say horses and zebras, jaguars and leopards, man and ape, a couple of scraps of fossil bone and said: “Oh, they look similar therefore one evolved from the other,” and created this “theory” about evolution out of thin air. There is far more to it than a few fossils. It is a massive corpus of facts, all woven together into a solid reality that exists all around us, for those who would look.
A while ago I was reading a book (David Rains Wallace, 2004, Beasts of Eden). I do do that, read books, sometimes it seems that that is all I do, is read. But I digress. The book was about mammalian paleontology, both the history of finding mammalian fossils and the evolution of mammals. It included an illustration with four skulls of titanotheres and their specific names arranged (bottom to top) in chronological order. Looking at the skulls (which had been restored to what they probably looked like in life) one could see how the skulls enlarged over time, the jaw/nose lengthening out of proportion to the rest of the skull, the horn moved from about halfway between the nostrils and the eyes, in stages, to the nose, and became larger and in the final skull the horn had a bifurcated tip (looked like a “Y”). The progress was steady by minor changes from species to species. How could anyone deny the evidence? Clearly the first species had evolved into the last. You would have to be willfully blind to refuse to accept the evidence. Or maybe not.
There were only four skulls presented, each from a different species, over several million years. There are similar illustrations for horses, with a few more species over tens of millions of years. After some reflection I realized that based on just what was shown in any of these illustrations, you could deny that they demonstrated the evolution of one species into another, and another, for millions of years until the descendant showed little obvious relation to the original ancestor. I might think you were being overly hard-headed, critical, and a knot-head, by refusing to accept the evidence but then I both accept evolution and know more about what’s behind the illustrations.
If you don’t accept evolution and don’t know (or refuse to know) what the illustrations are based on, how much more evidence exists than is shown, you can convince yourself that they don’t show any evidence for evolution. That is you could if there were only these four titanothere skulls or several horse fossils. For the sake of clarity a few of the species have a fossil chosen to represent the entire species. Sometimes a reconstruction, which may be a composite of several individual fossils, is used for the illustration. I know that the illustrated fossil is representative of a population of fossilized individuals. There is almost always more than one fossil from a species and they are not absolutely identical. Over period of 5-6 years I had the opportunity to spent up to two weeks prospecting for fossils. We spent most of the time searching the same area over again each year. The area is eroding so new material is being continually exposed. Anyway, the most common fossils found were Hyopsodus sp. mandibles (lower jaw bone). The portion (most of the tooth row) ranged from 1.5-2cm in length. I found from four to twelve each field season. The others I was with found more. I don’t know how many we found (there were other geology/paleontology crews in the immediate region also collecting fossils for other institutions) but the American Museum of Natural History (AMNH, where the fossils are curated) has to have hundreds to thousands of jaws from these animals. I have been to the AMNH (and the Kenya National Museum) and seen some of their fossil collection. The fossils on public display in the world’s museums are only a tiny, very tiny, part of their entire collection. They have drawers and shelves full. There may be only fossil remains of 12 different Tyrannosaurus rex in the world (it may be 15) and only a few hundred (not counting fragments) from the hominine species, but where there are thousands to tens of thousands of fossils from some invertebrate species there is no way that any illustration or figure can begin to show the variation present in a species. Neither can they show how the variation grades into another species over time.
It is true that there are some fossil species represented by a single specimen, a single fossil bone even. Australopithecus africanus was just a skull. It was years before more fossils were found that could be attributed to the species. T. rex is known from 12 (or maybe 15) individual specimens. I do not know how many fragments/fossil bones, etc. have been found but they are from 12 separate individuals (since I read that I have heard of the finding of several more individuals). Montana has the record number of finds, something like four including the first (and type) specimen. Some fossil species are rare and/or poorly known. Many extinct species are unknown and will never be known. The fossil record is and always will be incomplete. Having said that, the fossil record does contain much information, just remember that there are limits.
With a single fossil it can be very hard, if not impossible, to decide the sex, age, or size of the individual specimen it represents. You cannot know how close to being an “average” individual it is. The fossil Lucy (Australopithecus afarensis) is tiny and some of the arguments surrounding her are: is she just an unusually small individual or is she of average size for that species? Real species are populations of living organisms,. of all ages, size, and sex. Until you have a collections of numerous fossil representing the same species from a reasonably small period of time, just what is average or normal is difficult to determine. You have to tread very carefully.