Fossils allow scientists to develop a cohesive idea of the planet's makeup throughout its history.
The Precambrian Era represents seven-eighths of Earth's history, but the fossil record for the era is extremely poor. Precambrian, which means the era before the Cambrian period, refers to the period of Earth's history before the formation of the oldest rocks with fossils in them. However, some scientists have found some fossils in the Precambrian Era rock, although the fossils are extremely hard to discern and identify.
The Type of Fossils Found
The Precambrian Era, which is divided into the Hadean, Archean and Proterozoic eras, refers to anything before 600 million years ago. The oldest fossils that scientists have discovered have come from the Archean Era. These fossils appear to be blue-green algae formations that floated in the ocean about 3.5 billion years ago. These formations are thought to be single-celled bacteria, and they are the earliest form of life that anyone has yet to discover.
What Scientists Know About These Bacteria
These first set of bacteria that comes from the Archean portion of the Precambrian Era were most likely chemotrophs, which means that they produced hydrogen sulfide or carbon dioxide. These bacteria, which are called prokaryotes (or single-celled organisms) eventually evolved into multicelled organisms. Whereas the bacteria most likely had very little genetic diversity, they eventually formed all of the life that is present in the world today.
Other Fossils From the Precambrian Era
All of the fossils found in the Precambrian Era were bacteria, but the prokaryotic bacteria eventually evolved into multicelled bacteria with a little bit more genetic diversity and movement. These multicelled organisms are called the metazoans, and they appear as fossils in more recent rock layers that are from the Precambrian Era. They might have been more algae-like and had denticles, plates and tubes that allowed them to move. These multicelled organisms can be found both in the Precambrian Era and Cambrian Era.
Recent and Disputed Findings
In China, scientist Rolf Harris discovered a 650-million-year-old fossil that appears to have a more complex bodily structure than any other fossil that has been dated to the era. With what appears to be a possible eye, head-like structure and a body, this fossil causes some scientists to rethink their vast picture of geological history. The fossil has been named Wassahpdug Haldanei, and scientists still debate its authenticity.
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