For a basic 500 square feet project in zip code 47474, the benchmark cost to Insulate Your Home ranges between $0.63 - $1.43 per square foot* . To estimate costs for your project: 1.
So in answer to your question, the oldest fossils are stromatolites, and the life forms that created those fossils were prokaryotic bacteria and algae like cyanobacteria.
The Paleozoic Era is the beginning of an explosion of life forms. The Cambrian Explosion marks the era with thousands of new life forms in the ancient seas. There was certainly life before the Cambrian Period. There were even many complex life forms. In late Precambrian time was a period called the Ediacaran. Ediacaran fossils are found in the Ediacaran Hills of Australia, Northwest Territories, Yukon, British Columbia, and Newfoundland in Canada.