Answer:
prokaryotes
Step-by-step explanation:
Prokaryotes were the first living beings to appear on earth, about 3 billion years ago. By evolution, prokaryotic cells gave rise to eukaryotes.
At the beginning of our planet, the first forms of life should have a very simple cellular organization. This is because the planet still had inhospitable characteristics that would be unable to support more complex life forms. In this scenario, prokaryotes would be the organisms most likely to survive and thanks to their existence, the most complex forms of life were able to exist.