How do we know?

That's fair. We don't. Flip side of the question, though - what reason do we have for disregarding the current status quo other than egocentrism?

There's a lot of effort by the TESCREALists to redefine "life" to include their new favorite plaything, generalized artificial intelligence, so that they can discuss what rights Rosie from The Jetsons might be entitled to. I find this to be deeply disingenuous, considering their utter and total lack of interest in extending rights to, say, black people. "What is life" has taken on a new urgency now that the overwhelming majority of the world rejects the idea that ChatGPT is entitled to discount car insurance.

Schroedinger cribbed the Buddhists, Tegmark cribbed Schroedinger. That's fine, hard scientists can be philosophers, too. But my tail gets bushy when hard scientists pass philosophy off as science simply because that's what their degree is in. What function does this definition serve? Why are we defining it? What's wrong with the definitions we already have? What has changed that we now need to re-examine this question?

Because biologically and ecologically speaking, nothing has changed. We have not found any new goo armpit deep in a black smoker. Rama is ripping out of the solar system without so much as a chromatograph to remember it by. Nobody's discovered a cave of Sudoku-solving slime molds. What has changed is a whole bunch of too-online chinstrokers have started batting answerbots around and way way way too many of them want to turn their gullibility into profundity by arguing "I noticed it, therefore it matters."

Crichton's Andromeda Strain is literally about aperiodic crystals and whether they are entitled to rights as "life." Chrichton consequently digresses for a number of chapters on the definition of life and its reduction. He effectively concludes the question to be unanswerable but moot; regardless of the definition, "human life" takes precedence over any other.

That's the step that I see skipped in these discussions. And I see it skipped a disturbing percentage of the time.