What was the dominate life in the earth early formation?

The earliest forms of life that were the most dominant in the beginning were microscopic organisms that have left their trace in rocks.

Explanation:

The material these organisms had was able to stick to sediments. This material was only able to find in living organisms.

One of the first organisms that could do the process of photosynthesis was cyanobacteria. They were making food sing the sun and were releasing the oxygen.

After these organisms, the conditions for the first animals were made. The sponges were among the first animals.