Evolution was fueled by endosymbiosis, cellular alliances in which one microbe makes a permanent home inside another. For the first time, biologists made it happen in the lab.
Slightly clickbait-y title, but super cool and important discovery!
I found the following particularly interesting:
They also learned that in pairings that work, both partners adapt to each other — a phenomenon that has been largely overlooked. It wasn’t just the bacteria adapting to a new environment; the host changed too, even in the early stages. “That is a fundamentally important question that people have ignored,” Richards said. “This opens the doors for real advances.”
Framing it as what 'sparked complex life' is what makes it slightly clickbait-y. The circumstances which involved the creation of RNA/DNA is arguably more important when we talk about what 'sparked complex life', but it's really borderline and this is an important discovery and previous gap in knowledge so I think it's excusable here.