Paleontology is the study of ancient life; ancient life preserved as fossils.
During each of these years, over the whole world, the land and the water has been peopled by a host of living forms. What an infinite number of generations, which the mind cannot grasp, must have succeeded each other over the long roll of years! Now turn to our richest geological museums, and what a paltry display we behold! – Charles Darwin, The Origin of Species
What is a fossil?
Fossils can be defined as any non-living, biological material that can be interpreted in the record of life on Earth. We use fossils as data to make interpretations about the past. Fossils are incredibly important sources of information as they archive the past!
Fossils can give us information on the timing of events in the past. We can consider rates of trait change through time when we combine fossils with DNA and other molecular data. We can use fossils to think about the limits of life. Today, the largest land animal is the elephant weighing somewhere around 7-8 tons but long ago sauropods (long-neck dinosaurs) used to roam the Earth. Sauropods could be up to 135 tons in weight! That’s enormous! We can use sauropod fossils to examine how they lived as such large creatures. We can examine animal communities through time and think about why there are changes in the organisms in specific environments. We can also use fossils to think about long term evolutionary trends. This is called macroevolution, the study of large scale changes through time. To learn more about evolution click here. Fossils are our data points to study all of these things!
What do paleontologists do?
Paleontology is a very broad subject and paleontologists do a variety of different things but all with the same goal of understanding the history of life. Often times this involves going into the field to find specimens. “Field” is a broad term, this could mean the side of a road or in a remote desert. You can then compare the fossils you found to museum specimens, specimens in the literature, and even living organisms. You can usually identify them down to the species level or maybe you can describe a new species!
Paleontologists also keep a detailed record of where they find fossils, this includes information like latitude and longitude, what kind of rock it was in, how old the rock is, and what other organisms are found at the same location. From this information they can get ideas of past environmental conditions.
Many paleontologists have careers working at academic institutions such as universities and colleges where they can educate young minds and continue their research. Some work in museum collections as curators or collections managers. Those that work in a museum help organize the collections of life and often help create museum exhibits for the public.
Is paleontology a geological or biological science?
Paleontology is a combination of geology and biology. As a paleontologist you have to look at fossils as remains of living organisms or documentation of past life. You can think about the evolutionary history of organisms or even groups of organisms, the origination of groups, extinction events, rates of change, and even try to reconstruct how these animals used to live.
Additionally, fossils are rocks. They have undergone processes that have transformed them from biological material to geological material. Fossils are also found in rocks, the rocks that fossils are found in are called sedimentary rocks. These rocks can be used to determine other environmental conditions such as how deep the water was, how close the location was to the equator, ocean water conditions, and many other chemical signals.
How does a fossil become a fossil?
Fossilization represents the movement of biological information from the biosphere (biological material) to the lithosphere (rock material). There are many components that go into whether or not organism remains can become fossilized. There are also many ways that a fossil can be preserved in the rock record.
To learn more about the fossilization process head to the page ‘Types of Fossil Preservation’.
Composition of ‘hard parts’
What are organisms made of? This can be thought about in two general ways: (1) hard parts or hard skeletal tissues, such as bones, teeth, or shells and; (2) soft parts or soft tissues, such as internal organs. Generally speaking, hard parts are more resistant to decay than soft parts.Every organism has different amounts of hard and soft parts and often the soft parts are holding the hard parts together. Think about the ligaments and muscles that help you do simple tasks such as hold a pencil or walk! There are also differences in the composition (make-up) of hard parts. Most soft parts are made up of ‘organic matter’, these include lipids, carbohydrates, proteins. These all have a similar chemical make up that includes Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorous, and Sulfur. We like to abbreviate these organic chemicals and call them CHONPS!
Hard parts also have some organic material in them and are often composed of crystalline materials that form a fibrous material that is stiff and resistant.
Think about the exoskeletons of insects, as they grow they molt and grow a new skeleton to cover their soft bodies. This exoskeleton is different from your endoskeleton of bone in its chemical make up. There are several common types hard part chemical compositions: (1) Calcareous (calcite, aragonite; many shelly organisms); (2) Siliceous (diatoms) and; (3) Phosphatic (apatite; bone, including yours).
Head to the page on ‘Understanding Common Minerals in Biomineralization’ to learn more about the different minerals that animals build their skeletons with.
Taphonomy is the study of what happens to an organism after it dies. There are three main processes: (1) Necrology; (2) Biostratinomy and; (3) Diagenesis.
Necrology is the study of death processes. This includes how dead organisms or dead pieces of organisms are produced. Causes of death are often easily identified. This can be from visible tooth marks, breaking of hard parts, boring (drilling) by snails, fossilized feces (coprolites), and in rare cases burial in ash.
Biostratinomy is the study of what happens from the time an organism dies to the time it is buried. What are some common things that happen to organisms after they die?
There can be mechanical processes such as trampling or transport of the remains. Other animals feed on dead plant or animal tissue, these animals are called scavengers. Bacteria helps break down organic matter producing those gross decomposition gases. Changes in temperature and pH (acidity) also control how quickly an organism can decay. A variety of other things can happen to biological remains after death. Decay processes exist primarily because dead organisms are valuable sources of food for other organism.
Diagenesis is the study of the physical and chemical changes that occur after the organism is buried. Minerals in the hard parts of the organism are either left unaltered, dissolve, or undergo other fossilization processes. Physical changes include the remains being crushed or deformed by other geologic processes.
In some very rare cases, soft-bodied organisms (those lacking hard parts like bones and shells) are preserved or fossils are preserved in ridiculously high numbers or ridiculously well. These are called lagerstatten – generally termed the “motherload”.
When a really high number of fossils is preserved this is called a concentration deposit. Logically, there is a high concentration of fossils! These can be found as either shell beds or bone beds. Consider an owl pellet (vomit but in a matted mass) – this pellet is filled with hair and bones of animals the owl has eaten. This is considered a concentration deposit because it is filled with similar animals that the owl eats.
The preservation of soft-bodied organisms and soft parts of organisms is a bit harder, they are found in conservation deposits. In order for these soft parts to be preserved there must be a perfect storm of environmental conditions: (1) There must be very little oxygen, this is because if there is abundant oxygen other organisms will come to eat those soft parts; (2) Rapid burial (called obrution) must occur, this can happen in an underwater avalanche (called a turbidite) or other very fast events; or even (3) sealing of the organism by an overgrowth or microbial mats (essentially a floor mat, rug, or draping of microbes, imagine a huge mound of gelatin encasing the organism).
Can everything become a fossil?
Absolutely not!!! As paleontologists we think about the preservation potential of organisms a lot. Preservation potential is how well organisms and other biological information can be preserved. Remember, things with hard parts (shells, bones, etc.) are preserved better and more often than soft tissues (internal organs, ligaments, skin, etc.). So the more hard parts an organism has the more likely it is to be preserved.
Consider how many organisms are in an environment – the more organisms there are the more likely one of them will be preserved. Consider the type of environment… it’s really difficult to become a fossil on land but less difficult in the water! Water creates a more stable environment, on land there are different processes that work together to break down plant and animal matter. Wind and water (rain or streams) work to break down rocks and life on land.