Let’s talk fossils!! Let’s begin by discussing how fossils are formed because many people don’t really know what it takes for fossils to form. To begin with several processes have to take place in order for fossil formation to occur and no matter which of these processes causes the fossil to form it requires a bit of luck as most remains of plants and animals do NOT become fossils.
Freezing is one way of fossil formation and, in fact, is the best way although it happens rarely. In this process the remains (bones, shells, etc) must be continually frozen from the time of death until some bright-eyed Paleontologist comes along and digs them out of the ice. Most remains found in ice are from the last Ice Age which occurred between 110 kya (thousand years ago) and 12 kya. Many remains of mammoths and wooly rhinos have been found in the ice in the far northern reaches of Alaska, Canada, Greenland, and Siberia. Some are so perfectly preserved they look as if they are simply asleep. Flesh, hair, and even skin are often times found still intact on the animal. Some of these animals appear to have been Flash Frozen (frozen instantly) as they still have food in their mouths and stomachs. In fact, frozen mammoth fossils have been found with half eaten buttercups still in their mouths. In terms of fossil plants in these cold regions finds include fossil vegetation that is TROPICAL some with fruit still on the branches! Additionally, some animal fossil remains have been found frozen in what appears to be running motion as if they were trying to escape some cataclysm. Sometimes predator and prey have been found frozen together and one has to wonder what these animals were trying to get away from but that’s another story for a future post perhaps.
Desiccation (drying) is another process by which remains can become fossilized. Mummified remains of both humans and animals have been found fossilized by drying and, in fact, such drying was one method used by the ancient Egyptians to mummify their dead. Dried remains/fossils are found in arid regions of the world and most often the skin, organs, and other soft tissues are intact even though the person or animal has been dead for thousands of years.
Asphalt is another means by which remains can become fossils. Think the tar pits in downtown Los Angeles known as the La Brea Tar Pits. There are over a hundred pits at this site filled with sticky tar or asphalt which were formed by seeping crude oil through fissures in the earth’s crust. The lighter elements of the substance evaporated leaving only the sticky tar that tends to be rather thick. Hundreds of fossil bones have been found at this site including sabertooth cats, dire wolves, deer, and other prehistoric animal remains. Most of these fossils date to the Pleistocene and the majority of them have been dated to 10K–40 kya. Asphalt (tar) is a great preservative. Not only have perfectly preserved bones been found in the tar pits but shells, teeth, seeds, and even exoskeletons have been found at the site.
Amber is another means by which fossils can be formed. Remember the insect encased in amber in the Jurassic Park movie? Most of what we find encased in amber are small insects and spiders but some amber has been found containing preserved small lizards. How does this process work? An insect lands on a branch looking for food when it steps in sticky tree sap so the insect begins to struggle to free itself but it gets more and more entrapped in the sap the more it struggles. Soon the insect is completely entangled in the sap and it suffocates to death. Eventually the tree dies and falls over into a swamp filled with swampy water. During a course of a million years or so the tree rots and becomes a coal deposit and the sap with our insect still inside of it is polymerized and hardened into what we call amber. Time continues on and the coal bed is submerged in sea water and eventually the water uncovers the coal bed that was formed by all the dead rotting trees that fell into the swampy waters long, long ago. Erosion reaches the amber with our fossilized insect still encased in it and it floats to the surface because it is lighter than the salty water surrounding it. It then washes ashore and someone finds it, hopefully.
Another means by which fossils are formed is known as “Distillation” or, simply, Carbonization. This process involves plant or animal remains decomposing and leaving behind carbon. The carbon creates an impression in rock of the creature which is basically an outline sometimes with very excellent detail. So in this case what we have is an outline but not the remains themselves as they decompose.
Permineralization is another process that causes fossil formation. In fact, this is the MOST COMMON process of fossil formation. In this process minerals fill the cellular spaces in the remains and crystallize thus preserving the shape of the plant or animal as in the form of rock. Most often the original material of the plant or animal decomposes leaving only an impression behind. At some point another bright-eyed Paleontologist comes along and digs them up in the rock. Many dinosaur fossil impressions have been found formed by this process of fossilization.
Other processes that are conducive to fossil formation include volcanic ash, peat bogs, and sediment deposits (mud) but no matter what the process the conditions have to be just right and the remains must be preserved before the remains rot and disappear. If conditions are not completely right then no fossil is formed.
So now that you understand the basics of fossil formation let’s turn to dating! Just how to paleontologists date fossils anyhow?????
Most fossils are dated via the sediment they are found in. That is, the fossil itself gives no date of how old it is so we date the sediment or rock it was found in and assume that date is accurate (which may or may not be the case as I’ll explain later). This technique is a geological dating technique and is the most common dating technique when it comes to fossil remains. It’s called RELATIVE DATING. In this method we are dating the surrounding sediments the fossil is found it but NOT the fossil itself and that’s important to remember because geological dating of fossils most often yields some FANTASTICAL DATES in the millions or billions years old ranges! Fantastical? YOU BET! In fact, some of these dates are literally unbelievable in my opinion!!
Another common dating method for fossils is known as ABSOLUTE DATING. This technique involves analysis of the amount of radioactive decay in the minerals of rocks. It’s commonly known as Carbon 14 Dating or, simply, C14 Dating.
So, the way we determine fossil dates most commonly is by dating the rocks or sediments in which the fossil was found. We date the sediments above and below the fossil and determine the age of the fossil. We ASSUME a fossil will always be younger than fossils in the sediment beneath it and this is an assumption or principle known as “Superposition.” Sometimes we already know the age of a fossil because we’ve found previous fossils of the same species elsewhere in the same layer of sediment. Geologists call this “Lateral Continuity.”
When fossils are found on a cliff face it is easy to estimate how old the fossil might be via estimating the age of the sediment layers (strata) that can easily be observed on the cliff face. The oldest layer (strata) lies at the bottom of the cliff face while the youngest lies at or near the top. Newer sediments are always laid down on older sediment deposits, so it is commonly assumed. How do you “read” a cliff face? From the bottom up!
Amid all this there is something known as “index Fossils.” These are fossils used to date rock and sediments in which the fossils are found. Animal or plant fossils are the best examples in this method that lived a short time and are found in several places. Shelled relatives of the Octopus known as “Ammonites” make ideal index fossils. This method is commonly used in areas where there are or have been ancient deltas.
Radiometric Dating is yet another technique for dating fossils. Rocks contain some radioactive elements that decay by emitting energy and, thus, turning into different and more stable elements. This is known as “Radioactive Decay.” This decay takes place at a consistent rate for each radioactive element and we know, usually, how long it takes for half of the quantity of the element to change. This state of decay is known as “Half-Life.” After an additional half-life has passed the element will continue to decay to about a quarter of its original amount. After yet another half-life passes the element decays to about 1/8 its original amount and as more half-life’s pass the reduction of decay of the original element continues until it is nonexistent. Using this knowledge we can determine the date of the fossil which is basically a rock itself.
There are some other techniques used for fossil dating but I’m not going to go into them here and there are new techniques being developed that, hopefully, will give us more ACCURATE dates for fossil remains that what we have at present. Personally, I think Radiometric Dating is the best and most accurate technique but that’s my own personal opinion. I am most often suspicious of C14 dating because dates have been found to be inaccurate many times and sometimes broadly. For instance, what we originally dated using C14 in millions of years turns out to be only thousands of years using RM Dating!
So, in general, when we date fossils we are dating the rock and sediment above and below it but not the fossil itself. In my mind this causes problems and accounts for the fantastical dates I mentioned earlier. Consider these things: How do earthquake change the dates? How does flooding change the dates? What about volcanic eruptions and their spewing of sediment material that covers the fossil affect dating of the fossil? Our Earth is constantly changing and it always has been. Sediments and rocks change in composition and in place! There are land upheavals. Some land rises while other land sinks or submerges and all of these thing, geologically speaking, effect the sediments and rocks above and below the fossil and the layer the fossil is actually found in. If you are religious and believe God flooded the Earth in the time of Noah then if that is true it has fantastic implications for fossil dating as it would be such a global flooding would upset all rocks and sediments and that, in turn, would mean that few to NONE of our fossil dates are correct! And that is exactly the argument presented by Christians, Muslim, and Jewish theologians and it’s also the reason they don’t believe in a very old Earth nor do they buy the “millions…..billions….zillions of years ago” rhetoric. Instead the propose a young Earth theory based on creationism and say our fossil dates are grossly over exaggerated to say the least. Are they right? Fact is Earth Changes of any magnitude would have an effect on fossil beds even if to a small degree but that small degree might cause us to inaccurately date a fossil in the millions of years when, in fact, it is only a few thousand years old. And this has happened at times!
I’m a long-time supporter and advocate for more ACCURATE dating technique developments. This is especially true when it comes to assigning dates to ancient human ancestor fossil remains. I can handle human ancestors being around 1 or so million years old but anything beyond that I consider “fantastical” as I think most people do. In some cases the dates arrived at are so old that I think such dates are simply “wishful thinking.” In fact, I’ve often thought that there is something fundamentally WRONG with some of our assumptions and dating techniques! Sadly, however, instead of re-examining them and looking to how we can correct our errors we tend to go on the defensive and that does NOTHING! Science changes as new and more accurate information becomes available…or….at least it SHOULD. But some people are incapable of admitting they were wrong so they get all defensive and some even go into temper tantrums which, frankly, is beyond ridiculous. FACT is scientists are human beings and human beings make mistakes and when we find errors we should correct them rather than have temper tantrums and MOVE ON!! So what if someone’s ego is bruised! They’ll get over it…..eventually.
In conclusion let me add this. Since the time of Charles Darwin himself evolutionists have held the notion of a linear and upward evolution of humankind. That is, the notion has been that as an archaic species began to grow extinct and new and more evolved human species emerged. But, the FACTS indicate that this notion is NOT TRUE at all. In fact, the FACTS seem to indicate that throughout the history of our species several human ancestors COEXISTED sometimes for long periods of time!! Some theories point to Homo erectus surviving right up until 12 kya while others have them going extinct 200 kya! So which is it??? I tend to think the later is likely the accurate date instead of the former.
And then there are the theories being postulated by Dr Susan B. Martinez in her books about man being basically a hybrid of many combined species. I’m reading her book right now and although I do not agree with all she says or theorizes I do agree with much of it. One thing she proposes is that human evolution was never linear or upward, at least consistently. She suggests many species of man have always been and never evolved into anything but, rather, interbred creating hybrids and sometimes then interbred with more evolved species of man causing advancement for humans while at other times they interbred with less evolved species of man and, thusly, caused DE-EVOLUTION of man! Frankly, this theory of her’s might well explain some of the anomalies we find in the human fossil record as it seems sometimes we advanced for a bit in terms of technology, tool making, etc. while at other times we de-evolved and even sunk into the depths of barbarism. She proposes that there have always been several species of man and they all interbred and mixed producing hybrid and modern man today is basically a hybrid galore! Is this why we can see in modern people CLEAR features of H. erectus, H. habilis, Neandertal, and even Ardipithecus or Australopithecus? I think it likely, honestly. In her way of thinking human evolution is more of a up/down/rising/falling phenomena and not an upward progression (evolution) at all. I’ll be blogging more about Dr Martinez’s theories in the very near future. Let me just say here that some of her postulations are fascinating and likely true.
Paleontologists have been resistive to the notion that several species of ancient human ancestors may have coexisted for long periods of time in some instances. However, after having had to pull tooth and nail they are coming around to the possibility. I think that is a good thing and I think that in the end acceptance of this theory (fact) will give us a far clearer and accurate picture of human evolution, who and what we are (and are not), and how we came to be the species we are today.