For billions of years the microbes had the Earth, and all that was on it, pretty much to themselves.
Not that they did a lot with it that was very ostentatious or visible. They completely failed to develop private property rights, a legal system, retail shopping malls, or organised society as we know it.
One thing they did do, and did very well as they sat there in the primordial soup quietly evolving, was develop an ability to oxygenate the planet. A more oxygenated world ushered in the arrival of the first aerobic animals about 645 million years ago, and then us humans around 3 million years ago.
Paul Falkowski studies how the humble microbe has shaped human history in his book 'Life's Engines' (Princeton University Press).