Lv0 — Activity Era. Lv1 — Pure Gold Era. Lv2 — Pitch-Black Era.

There was no avoiding it: The Science of Activity Evolution, shaped in part by Shen Cong's influence, carried a certain dramatic flair in its terminology. And now the Jianhu County Laboratory team, shaped in turn by The Huoxue, had continued in the same spirit — Pure Gold, Pitch-Black. Vivid, slightly overwrought names for stages of bodily annihilation.

For Shen Cong, though, the classification wasn't theater. It was a map. A possible evolutionary path, laid out ahead of him.

Metallic transition and invasion — Shen Cong's framing. Metallic contamination — Nan Guohua's. Evolution — New Hefei's.

Whatever you called it, the research pointed to the same direction: metallic life was in the process of replacing carbon-based life. Metal was substituting for organic compounds, step by step.

Long before the Apocalypse, humanity had understood that carbon-based life wasn't the only possible model. People had speculated endlessly about extraterrestrial biology — machine intelligences, energy beings, silicon-based organisms, electromagnetic entities, information-based consciousness. Robots had attracted the most popular attention, producing the Turing test, the Laws of Robotics, the entire cultural apparatus of human anxiety about being replaced by something they'd built.

The replacement scenario had arrived. Just not from outside.

"Something this reminds me of," Nan Guohua said, "is a conversation I had years ago with my doctoral supervisor, working on the origins of life. We discussed what someone called 'metal cells' — a foam structure that used metal anions to mimic certain properties of living cells. At the time we were exploring the theoretical possibility of metallic life. I didn't believe metal cells constituted life."

He was referring to experiments by Lee Cronin at the University of Glasgow — an ion-exchange reaction between two saline solutions that produced inorganic chemical cells: iCHELLs. By modifying the metal-oxide backbone of these structures, Cronin had given them some properties of natural cell membranes.

But Cronin's iCHELLs could only be called cellular mimicry. They didn't qualify as fully living things. They couldn't carry genetic material analogous to DNA, and without that, self-replication and evolution…