It seems that Earth was a dull place from about 1.8 billion years ago to about 0.8 billion years ago. Mountain formation fell to nada, and over that time the mountains that had emerged prior eroded away. The land area of Earth was thus very flat. And seemingly along with that dull era of geology, biological evolution also seemed to stall out. There may be a link: mountain erosion leads to various mineral nutrients (such as phosphorus) washing out to sea… but as the mountains eroded away and weren’t replaced, the rivers of the time had less and less interesting stuff in them, and thus the single celled organisms int he ocean had less and less to work with.

But then the supercontinent of Nuna-Rodina broke up and mountain formation began again. In about 300 million years the Cambrian Explosion happened and the diversity of life  expanded vastly.

Earth’s mountains disappeared for a billion years, and then life stopped evolving

As mentioned in a  post about the Great Oxidation Event, the history of life on Earth is complex and deeply interconnected with the geology of the place. Life seemed to arise *very* soon after the planet got completely remade by getting plowed by a Mars-sized world, throwing off rubble that would become the moon; but even though there was life,  for billions of years it remained very simple. complexity only came about quite recently. But it’s far from certain that that’s the way it has to be. there might well be worlds that have major civilizations partying down just a few hundred million years after the place cools enough for liquid water.

And of course there are also the many continents that have been subducted and are now floating around in the mantle, hiding forever the traces of the advanced reptilian civilizations that rose and fell on them.