AI-Designed Self-Replicating "Xenobots," Shaped Like Pac-Man, Are Science Fiction No Longer

Scientists at the University of Vermont, Tufts University, and Harvard University have built what they say are the world's first self-replicating living robots, designed by artificial intelligence: Xenobots.

"People have thought for quite a long time that we've worked out all the ways that life can reproduce or replicate. But this is something that's never been observed before," claims co-author Douglas Blackiston, who worked to create the initial "parents" of the Xenobot family and handled the biological portion of the study — working with embryonic cells, which would usually be turning into frogs' skin.

"This is profound," claims co-lead Michael Levin. "These cells have the genome of a frog, but, freed from becoming tadpoles, they use their collective intelligence, a plasticity, to do something astounding. We have the full, unaltered frog genome, but it gave no hint that these cells can work together on this new task."

The task in question: Self-replicating, with the Xenobot "parent" self-replicating into tiny "babies," which in turn replicate into more — though it took an artificial intelligence to figure out how to prevent the process from stopping after a generation or two.

"We asked the supercomputer at UVM to figure out how to adjust the shape of the initial parents, and the AI came up with some strange designs after months of chugging away, including one that resembled Pac-Man," explains lead author Sam Kriegman. "It's very non-intuitive. It looks very simple, but it's not something a human engineer would come up with.

"Why one tiny mouth? Why not five? We sent the results to Doug [Blackiston] and he built these Pac-Man-shaped parent Xenobots. Then those parents built children, who built grandchildren, who built great-grandchildren, who built great-great-grandchildren."

The biological robots work through a process known as "kinematic replication" - something normally associated with molecules rather than cells. "We've discovered that there is this previously unknown space within organisms, or living systems, and it's a vast space," says co-lead Joshua Bongard. "How do we then go about exploring that space? We found Xenobots that walk. We found Xenobots that swim. And now, in this study, we've found Xenobots that kinematically replicate. What else is out there?"

To prove the Xenobots capable of useful work, the team simulated an incomplete circuit. As the Xenobots swam around, they pushed the components — eventually, given time, connecting a light emitter to a battery and completing the circuit.

The team's work has been published under open-access terms in the journal Proceedings of the National Academy of Sciences, while the source code that generated the Pac-Man like design is available on GitHub under the Creative Commons Attribution-NonCommercial 4.0 license.