This is Part 9 of a series of approximately sixty posts that outline evidence, support, and explanation for evolution. Receive updates and notification of all posts from dennismitton.com by selecting the follow button on the sidebar of any page. Thanks!
What kid doesn’t like a fossil? When I was young, I was fascinated with them: here, in my hand, in this tiny piece of amber, is an even tinier ant who crawled up some unknown pine a million years ago and was trapped in sap. What a sad fate! Crawling along, eating, feeding, defending, and then? A stuck foot and an oozing encasement around your leg that finally engulfs your entire body and suffocates you. And the dinosaurs reconstructed by fossilized bones? My favorite was the pterodactyl – what kind of world was it when creatures like this darkened skies like crows? Amazing stuff! This window into the past is one of the true wonders of science. Fossils speak of long gone creatures and plants. Granites tell us about volcanoes come and gone. Even our own bodies, especially in development, give hints of a common ancestry between humans and other organisms. It’s a rare soul that isn’t filled with a little wonder when holding a fossil. Maybe we should do more of it?
Fossils, simply put, are the remains of dead organisms, their impressions, or things related to their activities. Many fossils, similar to the ant above, are smallish plants and organisms that wind up inside an encasement of some sort with amber being most common. The uniqueness of these fossils is that the organism is preserved in their entirety allowing us to actually hold in our hand a creature a million years old. It’s hard to wrap one’s head around. Other fossils, of course, are enormous. I’ve stood under an articulated copy of Argentinosaurus and its size is boggling. One hundred and thirty feet long and 200,000 pounds when alive. Now that’s a huge lizard. The first bone was discovered when a farmer in Argentina found what he thought was a huge piece of petrified wood. More digging revealed more bones and they figured out the ‘petrified wood’ was a tibia. Every imaginable kind of organism large or small can be found fossilized in some way – even bacteria.
Fossilization is rare and requires that several things line up just so. In most cases, water is needed, as is a quick covering, and time left undisturbed for geology and hydrology to do their work. In other cases, it’s just bad luck – a mammoth falls into a crevasse and is covered in snow and remains frozen under what seems to be an eternal winter until modern folks dig it up through other activities. Because of the difficulty of fossilization, it’s routinely estimated that possibly only five percent of all animal species have fossil representatives with the great bulk of those existing as marine creatures. Common types of fossilization include encasement as described above, imprints or molds, freezing, and perimineralization where water-borne minerals seep through bones and fill cavities within the structure. This last item is what we usually think of when someone uses the term fossil.
It’s easy to imagine why most fossils are car-wrecks of preservation. How many pristine and clean skeletons have you seen lying about the woods or the road-side? I run a lot and see plenty of bloated carcasses of dead things along the road – it’s common that in just a few days they are gone without a trace, dissected, eaten, and partially carried off by scavengers. It’s one reason why we so often find just a few bones rather than articulated skeletons. But sometimes we luck out and find extraordinarily detailed remains. Archaeopteryx – the famous transitional between reptiles and birds – is so finely preserved that the patterns of its feathers can be made out. Some plants, especially those found in water, are very finely preserved with exquisite detail.
What do they mean?
In a real way fossils led early scientists and naturalists to ideas about evolution. Museums were stuffed with fossils that begged questions as to what they were and how old they were. The Biblical Flood was the most obvious answer to many Westerners. No one had ever seen any of the animals and no ancient books told stories of doing battle sitting on the back of a trained Ankylosaur. Clearly, the fossils were from a different era. Even plant fossils painted pictures of landscapes foreign to what we have known in our history. As more fossils were collected, it was noticed, too, that certain types of fossils appeared in certain type of rock. Soon naturalists were able to predict what kind of fossils would be found in particular formations. That the same fossils could be found in the same rock separated by hundreds or thousands of miles bolstered the geology of uniformitarianism and later, early ideas that led to plate tectonics.
Fossils also revealed a general pattern. As the nascent science of dating evolved (these were the days before radiometric analysis), it was clear that fossils revealed that, based on the geologic law of superposition, a gradual increase in complexity of body function and development through time. A useful geologic column was developed that provided a framework and place keeper for more discoveries. Transitional forms – those organisms with adaptations that are now recognized as representative of an earlier and then a later organism – could be identified, with Archaeopteryx as the most famous. More recently, researcher Neil Shubin, as detailed in his book, Your Inner Fish, has found the transitional creature Tiktaalik – the fish with hands – exactly where he predicted that he should based on the geologic column (see Part 4). Much has been made of these ‘missing links’. Darwin bemoaned that without them his new ideas would be difficult to prove. A hundred and fifty years of hard work, though, has proved time and again that, at least regarding the fossil record, he was prescient in his expectations.
The fossil record also teaches us about natural selection. We see periods of extinction where the environment changes in such a way that existing species struggle to survive in. Within these same times, we see entirely new kinds of organism flourish and develop as novel niches open for populating. The early Cambrian Explosion and the development of mammals are the best-known examples of this niche exploitation.
Interestingly, fossils also show us that not all things must change. Living fossils are organisms that appear unchanged through much of geologic time. Alligators are a common example as are several types of prehistoric looking fish. People ask why these haven’t changed through evolution? In many cases, they have – using genetic analysis we see that they are different genetically without visible exterior changes. But evolution doesn’t require wholesale change. If an organism is successful within its environment, it will remain so until something more successful displaces it. It’s clear that crocodiles, sharks, and coelacanths have figured out how to be the best at what they do. Time will tell if humans make it onto that list.
There are no arguments that I know of against the presence of fossils – when creationists moan about any lack of evidence for evolution they do a quick two-step and start on about dating (to be described in a soon upcoming post). Even these masters of avoiding the obvious can’t skirt around a thousand pound Argentinosaurus tibia. But it shouldn’t surprise anyone that they try. There was a time when fossils, both animal and human, were talked about as a test sent from a rather impolite God. He made them, it was argued, to test the faith of the faithful. True believers pooh-poohed fossils even if people made fun of them. Another argument, rarely heard today, is that God was experimenting or practicing. This was my Grandfather’s belief. It’s not exactly what I would expect from the perfect God that we are told about today. Of course, as with all religious answers, there is really no way to disprove these. It’s a matter of faith that is unassailable.
A common young-earth Creationist argument is that dinosaurs roamed the earth along with Adam and Eve in Eden but were wiped out during Noah’s flood. I’m not sure why dinosaurs specifically would be exterminated – maybe someone can fill me in? This view, though, is contradictory to everything we know about geology, physics, dating, biology – well, I could just go on.
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Don’t think it’s a child’s book only. Informative and useful.
I haven’t purchased these but the set looks very cool!