Prior to 560 Myr ago, organisms left little in the way of remains or imprint to mark their presence and their passing. However, we can use other evidence to learn about the origins and early evolution of life. Oxygen had yet to appear in much abundance, and wouldn't until the rise of photosynthesis some time later. One of the difficulties in defining when life began is deciding on what actually constitutes life. However, enzymes and other compounds that control chemical reactions do that quite nicely on their own, yet we wouldn't call them alive.
Life is the ability to move around in one's environment.
However, lichens don't move appreciable amounts during their lifetimes, yet they're clearly alive. Life is the ability to grow and maintain a particular body shape or form. Mineral crystals fit those requirements, as they grow in response to a particular distribution of bonds and bond energy. This is still not really satisfactory - certain arrangements of atoms or clay minerals are perfectly capable of the same thing, though they lack the internal energy source that allows living organisms to replicate spontaneously . The other concepts outlined above are part of the package as well, but life really entails reproduction.