Short story: man creates a computer simulation with crab-like beings, stops death after one sentient generation

Question

I read this a few years ago online: a man creates some kind of simulated world using a quantum computer with creatures that end up evolving to look 'crab-like'. He's able to fast-forward the simulation; after fast-forwarding to where they're of human-level intelligence and grieving over their dead, he is emotionally unable to let them continue dying. That generation lives forever and (I believe) he stops them from being able to reproduce, so the population is entirely stagnant immortals. At some point he establishes contact with a crab-being, but only one.

Does anyone else remember reading it, what it was called, or what the website it was hosted on could have been?

Answer 1

It's "Crystal Nights", by Greg Egan.

“You created this world?” Primo asked him.

“Yes.”

“You shaped our history?”

“In part,” Daniel said. “Many things have been down to chance, or to your own choices.”

“Did you stop us having children?” Primo demanded.

“Yes,” Daniel admitted.

“Why?”

“There is no room left in the computer. It was either that, or many more deaths.”