What are stromatolites, and why are they evidence of very early life?. Earth & Marine Sciences

Stromatolites are ancient rocks found in some of the oldest geological formations on Earth. They bear striking microscopic similarities to large mounds built by colonies of bacteria alive today. Although these formations are rare on Earth today, they are abundant in the early fossil record. So, stromatolites are not only evidence of early bacterial life, they may be important to understanding life on Earth 3.45 billion years ago.