When did the first prokaryotes emerge?

The emergence of the first prokaryotes is widely accepted to have occurred around 3.5 billion years ago. This timeframe is supported by a variety of geological and fossil evidence, including stromatolites, which are layered structures formed by the activity of microbial communities, primarily bacteria. The presence of these ancient structures indicates that prokaryotic life was thriving in the oceans during that period, making it a critical point in the history of life on Earth.

Being one of the earliest forms of life, prokaryotes are significant because they played a fundamental role in shaping the planet's early environment, including contributing to the development of Earth's atmosphere through processes like photosynthesis. This emergence marked the beginning of biological evolution, leading to more complex life forms over billions of years. The other options, while they represent other significant events in Earth's history, do not align with the established timeline for the origin of prokaryotic life.