What is the oldest fossil in the world

Fossils are remains or marks of living organisms that have inhabited the planet at some point throughout its existence and that through different processes have preserved some of their body structures. They are important because they allow us to know the organisms that have inhabited the Earth and the evolution of living beings on it. But what is the oldest fossilized organism?

What are fossils and how are they formed

As we said, fossils are remains or marks of organisms that have inhabited the Earth , which does not mean that they are necessarily structures of your body, but they can also be footprints, marks of some parts of your body, eggs, nests or excrement. , in short, everything that gives proof of the existence of a living being. These are often called ichnofossils . Thus, we can find fossils of animals of all kinds, plants or bacteria, both whole and fragmented structures.

The most frequent fossils are found in rocks, but we can also find fossils in ice, amber or in tree sap and, although they can belong to any type of organism, the most common is that they belong to organisms that had hard parts in your body, as these parts are more likely to resist decomposition conditions. Some processes that can generate fossils are:

  • Mineralization: In this process, minerals are added or modified to body structures. It is quite common among hard parts such as tree trunks, large bones or shells.
  • Carbonization: this process occurs when there is a loss of volatile substances such as oxygen, hydrogen or nitrogen, until a carbon film is left. It is common in plant or animal remains with lignin, chitin, cellulose or keratin and usually occurs in organisms that are crushed by rocks.
  • Foundry and molds: they are negative or positive impressions of the parts of the organism or its ichnofossils.

These are considered the oldest fossils on the planet and date back to about 3.5 billion years (the Earth is 4,500 years old and cellular life is thought to have started 3.8 billion years ago). These organisms were neither dinosaurs nor trilobites nor ammonites, but the oldest fossils are bacteria . Specifically, it is thought that stromatolites are made up of microbial masses composed of anoxygenic prototrophic filamentous bacteria (photosynthetic bacteria that do not produce oxygen) and cyanobacteria associated with calcium carbonate sediments.

Some stromatolites have been found throughout the planet, mainly in Australia and South Africa. The oldest known was the one found in Pilbara (Australia) in the 1980s and it was dated at 3.496 million years.

Recently, what are the oldest fossils dated to date have been discovered . These are microbial fossils from 3.77 billion years ago , less than 1 billion years after the Sun and Earth formed.

The study was published in the journal Nature recently and is led by a team from the University of College London (UCL) . The remains were found on a beach in Nuvvuagittuq (Quebec, Canada), the same place where some of the oldest sedimentary rocks on the planet have been found, dating from 3.7 to 4.2 billion years ago.

The marks of these fossils have been found between layers of quartz, at a site where there was a hydrothermal source that released hot mineral-rich water. This team identified conserved filaments in the sediments, which belonged to a species of primitive bacteria. Already during their identification, they ruled out any non-biological origin of these fossils, showing that they would not have been formed by changes in temperature or pressure on the rock. These fossils had a type of branching characteristic of iron-oxidizing bacteria, such as those found in other hydrothermal vents.

These fossils suggest that the Earth had conditions suitable for life earlier than previously thought and that life arose in hydrothermal vents on the seabed and later developed outside the aquatic environment.

Another curiosity is that conditions similar to those of the Earth at that time have been found on other planets and moons, such as in ancient oceans of Mars, underground oceans of Europa (Jupiter’s moon) and in a satellite of Saturn known as Enceladus.

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