fossils: The skeletons of the past

Layers of sediment trap buried organisms as decay and soil accumulate on top. Through this process, sedimentary rock is created. At the same time, the most common form of fossilization occurs. Carbon impressions of organisms are created in sedimentary rock, after hydrogen and oxygen are released from the remains; this is called carbonization, or distillation.

Other forms of fossilization exist. Petrification, also called permineralization, involves water seeping into the remains of an organism, forming crystals. Replacement, another method, is exactly as it sounds - minerals in groundwater replace the insides of bones, hardening this mineral along with sedimentary rock. In the process of casting, fossils can impress their exterior on sedimentary rock when they dissolve. The total sum of all fossils—discovered or undiscovered—is called the “fossil record”.

Rarely, organisms can be fully preserved when frozen, dried, or encased in materials like resin. An even rarer case is soft tissue, like flesh, being preserved in rock the same way bones and cartilage are. One case of this was a whorled shell, or ammonite, that had lost its shell. Its insides were imprinted on stone and discovered 150 million years later in January 2021.

One imprinted rock or crystallized bone contains immense amounts of information about history. Through radiometric dating, a scientist can determine the age of the materials in each fossil. After categorizing organisms into time periods, scientists were able to discover patterns. For example, the gigantic size of prehistoric mammals could be directly tied to the extinction of dinosaurs, whose disappearance resulted in an overabundance of fauna for mammals to consume. Dating of a variety of dinosaur fossils, as well as those of massive mammals like the indricotherium - a hornless rhino that lived around 30 million years ago in the Oligocene epoch - was crucial to the scientific conclusion.

Furthermore, the study of fossils is important to understanding human society. A healed femur bone fossil, dated 15,000 years into the past, provided us the most important knowledge about our civilization - what “civilization” truly meant. Margaret Mead, a cultural anthropologist, called it the “first sign of civilization.” In physician Ira Byock’s novel, she explained that someone had to tend to the person who broke their leg; this was impossible if a human only cared for their own survival, since animals are eaten before they can heal. Mead stated that “helping someone through difficulty is where civilization starts.” Through studying fossils, scholars pinpointed where survival turned from an individual to a community goal. 

Fossils are keys to the treasure of the past - gigantic reptiles wiped out by asteroids, sabre-tooth tigers frozen in ice, survival instincts turned into civilization. The same way a bone imprint might shape a rock, discoveries made from fossils shaped what we know of the world today. 

Castro, Joseph. How Do Fossils Form? https://www.livescience.com/37781-how-do-fossils-form-rocks.html. LiveScience, 21 September 2015

Imbler, Sabrina. This Ammonite Was Fossilized Outside Its Shell. https://www.nytimes.com/2021/01/31/science/ammonite-fossil-jurassic-paleontology.html?searchResultPosition=3 The New York Times, 31 January 2021. 

Blumenfeld, Remy. How A 15,000-Year-Old Human Bone Could Help You Through The Coronacrisis.https://www.forbes.com/sites/remyblumenfeld/2020/03/21/how-a-15000-year-old-human-bone-could-help-you-through-the--coronavirus/?sh=663ebd3a37e9 Forbes, 21 March 2020. 

Hecht, Jeff. Why mammals grew big – and then stopped. 

https://www.newscientist.com/article/dn19771-why-mammals-grew-big-and-then-stopped/ New Scientist, 25 November 2010.