A long time ago Earth was a very different place. Millions of years of constant change led to the world we know and live in today. Trying to observe that past world, so different and yet so similar to ours, seems attractive itself, however, it has an additional value. Learning about the history of life teaches us also about evolution, and therefore- our own origin. Let’s start this series by looking at different disciplines that help us understand the history of life.
Paleontology- the Study of the Past Life
The term paleontology refers to the study of life that existed before the current geological epoch- The Holocene. This discipline takes on topics like the physiology, evolution and relations of past organisms. It also studies the inorganic past of Earth. All of that makes it an interesting combination of historical and experimental science. It also relates a lot to biology and geology, often using tools from even more sciences. The most commonly known method used by paleontologists is probably analyzing fossil record. Fossils are all kinds of traces and remains of organisms from before our age. Body fossil is usually the remains of hard tissues. They are quite rare because of all the processes that can occur to them during such a long time (imagine lying in the dirt for at least 11,700 years!) Trace fossils, on the other hand, are just a sign of biological activity, like foot traces.
Geology In Studying the History of Life
Geology, despite being the study of non-living forms, contributes a lot to studying the history of life. Firstly, geology studies the structure of Earth, and beneath, uncovering layers of very old material. Then, it also provides information on age of said material, and determines its history. Therefore it enables the organization of timelines and gives information about the history of Earth. Methods used by geologist include work in the field, collecting the material, and then analyzing it using tools from chemical engineering, physical experiments and simulations. All that provides major evidence for a history of life. Geologists also work on understanding past climate changes and its causes, for example, a connection between plate tectonics and the Cambrian explosion.
Other Tools in Studying the History of Life
History of life is a complicated matter, so we can expect that studying it will require many different methods. Despite discussed paleontology and geology, there are a few more quite important fields. We can suspect that there will be some biology involved, the same goes for evolution studies. However, that is far from what we need. Paleoanthropology and archaeology include the study of evolution, behavior of humans. Biogeography helps with finding patterns in the adaptation of organisms. Ecology helps to describe the relations between species in the environment. Taxonomy makes it possible to place them in genetical relations with each other. Including all of the important fields would take much more time and space, but that is not what we are going for. Scientific disciplines are all connected. If we want to discuss the history of life, we need to include various disciplines, and find the connections between them.
The Geological Time Scale
Combining solutions from different fields helped with creating a geological time scale (GTS). It shows the current view on development of life on Earth. We will use it to navigate through the series. Before analyzing it, let’s get familiar with basic time units. Eon is equal to a billion years. Eons are divided to eras, which do not have a fixed number of years, but their division focuses on similarities of life forms. Lastly, periods are subdivisions of eras, their length depends on a system of dating analysis. There are four eons. Hadean starts with the formation of Earth, and ends with the beginning of life. Archaean involves the formation of continent and ends with raising the amount of oxygen. In Proterozoic first eukaryotes and multicellular forms appeared. Lastly, there is Paleozoic, started by the Cambrian explosion, divided into 6 eras, and that is the eon we live in.
I hope you the first article from the History of Life series gave you the basic information you need for a good start. If you enjoyed it, please share with family and friends. For additional information about evolution check out my Theory of Evolution series. If you ever want to contact me, feel free to write, you will find my email in the author’s section. In the next article we will discuss the Hadean and Archean eons, so stay tuned!