A hypothesis I'd seen (from the "aliens" guy, Abraham "Avi" Loeb, at Harvard) is that early in the evolution of the Universe everything was roughly in the Goldilocks zone (warm enough for liquid water, not so hot as to generate steam, not so cold as to result in ice), and ... more dense. If life more-or-less inevitably arises under such circumstances, then there's some credence to the argument that life might have arisen in many parts of the Universe, potentially hybernating in some sort of spore / inactive form, until rocky planets arose later. But we have no specific proof of this, and it seems strongly plausible that life could instead have arisen independently on individual planets and/or moons.

See this thread: <https://news.ycombinator.com/item?id=37850997>.

From which:

Kurzgesagt did a video on the concept: <https://www.youtube.com/watch?v=JOiGEI9pQBs>.

Avi Loeb, "The habitable epoch of the early Universe". International Journal of Astrobiology, vol. 13, 4."

<https://www.cambridge.org/core/journals/international-journa...>