AI-designed Xenobots reveal entirely new form of biological self-replication which could prove promising for regenerative medicine.
Birds do it, bees do it… now even living robots do it. Scientists at the University of Vermont, Tufts University and the Wyss Institute for Biologically Inspired Engineering at Harvard University have discovered an entirely new form of biological reproduction – and applied their discovery to create the first-ever, self-replicating living robots.
The same team that built the first living robots – xenobots, assembled from frog cells – has discovered that these computer-designed and hand-assembled organisms can swim out into their tiny dish, find single cells, gather hundreds of them together, and assemble “baby” xenobots inside their Pac-Man-shaped “mouth”. Amazingly, just a few days later, these become new xenobots that look and move just like themselves. And then these new xenobots can go out, find cells, and build copies of themselves. And so on and so on…
Longevity.Technology: There’s a lot to unpack here, and apologies if you are left bouncing between trying to reconcile the image of of robots gathering baby ingredients in their mouths like Pac-Man chomping up dots and checking to see if today really is the day Skynet goes online. Although I for one will be welcoming our new robot overlords, the research isn’t there quite yet, but it is remarkable – biological self-replication that given enough building blocks could be perpetual. A regenerative tool of extremely significant consequence.
“With the right design – they will spontaneously self-replicate,” says Joshua Bongard, PhD, a computer scientist and robotics expert at the University of Vermont who co-led the new research which is published in the Proceedings of the National Academy of Sciences.
Into the Unknown
In a Xenopus laevis frog, these embryonic cells would develop into skin – but the researchers had different plans. “They would be sitting on the outside of a tadpole, keeping out pathogens and redistributing mucus,” says Michael Levin, a professor of biology and director of the Allen Discovery Center at Tufts University and co-leader of the new research. “But we’re putting them into a novel context. We’re giving them a chance to reimagine their multicellularity [1].”
And given a multicellular inch, it would seem xenobots might just take a multicellular mile.
“This is profound,” says 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 [1].”
In earlier experiments, the scientists were amazed that xenobots could be designed to achieve simple tasks, but this research is a whole other level of amazing; biological objects – computer-designed collections of cells — will spontaneously replicate. “We have the full, unaltered frog genome,” says Levin, “but it gave no hint that these cells can work together on this new task,” of gathering and then compressing separated cells into working self-copies.
“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,” says Sam Kriegman, the lead author on the new study, who completed his PhD in Bongard’s lab at UVM and is now a post-doctoral researcher at Tuft’s Allen Center and Harvard University’s Wyss Institute for Biologically Inspired Engineering [1].
On its own, a xenobot parent, made of some 3,000 cells, forms 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. However, using an AI program working on the Deep Green supercomputer cluster at UVM’s Vermont Advanced Computing Core, an evolutionary algorithm was able to test billions of body shapes in simulation — triangles, squares, pyramids, starfish — to find ones that allowed the cells to be more effective at the motion-based “kinematic” replication reported in the new research [2].
“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,” says 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 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 [1].” Words with longevity promise – getting the right design can greatly extend the number of generations.
Kinematic replication has been well-documented on a molecularly level, but according to the researchers, it has never been observed before at the scale of whole cells or organisms.
“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? [1]”
Or, as the authors put it in their Proceedings of the National Academy of Sciences paper: “life harbors surprising behaviors just below the surface, waiting to be uncovered.”
Responding to Risk
It’s an exhilarating ride, but it is understandable that there might be some concern about self-replicating biotechnology. For the team of scientists, however, the goal is deeper understanding.
“We are working to understand this property: replication. 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. “What presents risk is the next pandemic; accelerating ecosystem damage from pollution; intensifying threats from climate change. This is an ideal system in which to study self-replicating systems. We have a moral imperative to understand the conditions under which we can control it, direct it, douse it, exaggerate it. 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 [1].”
Towards regeneration
This technology smacks of promise for the field of regenerative medicine.
“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,” says Levin. “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 [1].”
[1] https://wyss.harvard.edu/news/team-builds-first-living-robots-that-can-reproduce
[2] https://www.pnas.org/content/118/49/e2112672118
