How old are stromatolites, the oldest known fossils?

Stromatolites are indeed known to be some of the oldest fossils on Earth, with scientific evidence suggesting they date back to approximately 3.7 billion years. These structures are formed by the activity of cyanobacteria, which are among the earliest known life forms. The significance of stromatolites lies not only in their age but also in their role in shaping the early Earth’s atmosphere, contributing to the production of oxygen through photosynthesis. This process played a crucial role in the development of life as we know it today.

In the context of the available choices, while other options mention significant geological time frames, none of them accurately capture the remarkable antiquity of stromatolites, which are recognized as indicators of early microbial life. Thus, the choice citing approximately 3.7 billion years accurately reflects their historical significance in the geological record.