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.
Fossil stromatolites are the oldest known life forms on earth up to 3.5 billion years. Picture #: 071518. Image of a stromatolite, a limestone accretion formed by cyanobacteria, Hamelin Pool, Shark Bay, Western Australia, Indian Ocean; may be up to 1000 years old.