BURLINGTON, Vt. — The era of humans building robots may be over. Scientists from the University of Vermont, Harvard, and Tufts University have created what they describe as “living machines” which can reproduce just like organic life.
The team says they’ve discovered an entirely new form of biological reproduction, which they used to create the first-ever self-replicating robots. Scientists built these “Xenobots” out of frog cells, which they designed with a computer and assembled by hand.
In a scientific stunner, the new study reveals the tiny bots are capable of swimming out of a lab dish, find and collect cells, and use those cells to assemble a brand new “baby” Xenobot. Just a few days later, this new robot is capable of going out and replicating as well.
“With the right design — they will spontaneously self-replicate,” says Joshua Bongard, a computer scientist and robotics expert at the University of Vermont, in a release.
A whole new method of replication on Earth
Researchers say the embryonic cells from the Xenopus laevis frog normally develop into skin cells. They would typically sit on the outside of a tadpole and keep out viruses.
“We’re putting them into a novel context. We’re giving them a chance to reimagine their multicellularity,” says Tufts University professor of biology Michael Levin.
“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,” adds co-author Douglas Blackiston, the senior scientist at Tufts who assembled the Xenobot “parents” and developed the biological portion of the study.
“This is profound,” Levin continues. “These cells have the genome of a frog, but, freed from becoming tadpoles, they use their collective intelligence, a plasticity, to do something astounding.”
Earlier tests on the Xenobots revealed that scientists could program the living machines to carry out simple tasks. However, this new study reports on their ability to spontaneously replicate.
“We have the full, unaltered frog genome, but it gave no hint that these cells can work together on this new task,” Levin explains.
Study authors found that — using a Pac-Man-shaped mouth — the “parent” robots gathered and then compressed separate cells into working copies of themselves.
“These are frog cells replicating in a way that is very different from how frogs do it. No animal or plant known to science replicates in this way,” reports lead author Sam Kriegman.
Gobbling up cells like Pac-Man
On their own, the team says each Xenobot consists of around 3,000 cells which typically form a sphere.
“These can make children but then the system normally dies out after that. It’s very hard, actually, to get the system to keep reproducing,” says Kriegman.
To fix this, the team turned to an artificial intelligence program which used an evolutionary algorithm to test all sorts of different shapes which might help the robots replicate without dying off. The AI program settled on the simple, single-mouthed design (similar to the video game hero Pac-Man) as the best option for motion-based “kinematic” replication.
“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,” Kriegman continues. “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 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.”
Scientists note that kinematic replication is a common process at the molecular level, but it’s never been seen among cells and organisms (or robots) of this size.
“We’ve discovered that there is this previously unknown space within organisms, or living systems, and it’s a vast space,” says Bongard, a professor in UVM’s College of Engineering and Mathematical Sciences. “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?”
What could self-replicating robots do for humanity?
Although researchers admit that many people will have concerns about robots which can build more of themselves, they believe understanding the technology will ultimately lead to many benefits.
“The world and technologies are rapidly changing. It’s important, for society as a whole, that we study and understand how this works,” says Bongard. “The speed at which we can produce solutions matters deeply. If we can develop technologies, learning from Xenobots, where we can quickly tell the AI,: ‘We need a biological tool that does X and Y and suppresses Z,’ — that could be very beneficial. Today, that takes an exceedingly long time.”
Study authors are hoping these robots will one day be able to pull microplastics out of waterways or create new medicines for future viruses.
“If we knew how to tell collections of cells to do what we wanted them to do, ultimately, that’s regenerative medicine—that’s the solution to traumatic injury, birth defects, cancer, and aging,” Levin concludes. “All of these different problems are here because we don’t know how to predict and control what groups of cells are going to build. Xenobots are a new platform for teaching us.”
The study is published in the Proceedings of the National Academy of Sciences.