Precambrian-Cambrian transition

The Precambrian-Cambrian transition marks a pivotal moment in Earth's history, occurring approximately 541 million years ago. This period signifies the end of the Precambrian, which spans over 80% of geologic time and includes the Archean and Proterozoic eons. While early life forms existed in the Precambrian, including microfossils resembling algae and the first multicellular organisms, the transition to the Cambrian Period saw an unprecedented "explosion" of life.12

The Ediacaran Period, the final part of the Precambrian, witnessed the evolution of the earliest known multicellular animals, known as Ediacara fauna. These were unusual soft-bodied invertebrates. The transition was also influenced by significant environmental changes, such as the retreat of ice sheets and rising oxygen levels. The Cambrian Period then saw the rapid emergence of many major animal phyla, characterized by the evolution of hard body parts like shells, which fossilize more readily. This diversification laid the groundwork for the complex ecosystems that followed.345