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Eukaryotes are colored red, archaea green and bacteria blue. The image was generated using iTOL: Interactive Tree Of Life
Some 3.7 to 2.7 Billion years ago our oldest ancestors popped out of nowhere on a "with huge quantities of water cooled down lava blob". Some basic forms of RNA strands started the whole of us.
In the beginning there was no oxygen to breathe, but here was water to dissolve salts and the underwater volcanic chimmneys to warm. ARCHAEANS were the only living beings able to live there by doing methanogenesis.
They also have lived on the shores of the prehistoric oceans; where the water meets the lava land and finds the little cavities and fills them with dissolved chemicals. EUBACTERIA, with a rigid body and a flagella to move around was there. Temperatures where high too on the lava shores for uncountable intervals of time. Many eubacteria form spores, resistant to dehydration and most temperatures, when there is no food and can last up to 50 years.
The perfect habitats for thermophyles, our first common Grandparents. For nearly 2.7 billion years, all organisms were microscopic. ARCHAEANS, EUBACTERIA and BACTERIA where the only habitants. Viruses were there already too probably, because of their molecular simplicity.
Three shore families and one underwater family.