Scientists create 'living' robots that can reproduce themselves
To exist, life must continue and reproduce. Over billions of years, organisms have developed many ways of reproduction, from budding plants to sexual animals and viruses.
Now scientists from the University of Vermont, Tufts University and the Wyss Institute for Biologically Inspired Engineering at Harvard University have discovered a completely new form of biological reproduction and used their discovery to create the world's first self-replicating living robots.
The same team that created the first living robots ("xenobots", made from frog cells, first reported in 2020) found that these computer-designed and hand-assembled organisms can swim in their tiny "dish", find individual cells, gather hundreds of them together and assemble "little" xenobots inside their Pac-Man-shaped "mouth".
After a few days, they become new xenobots that look and move exactly like their "parents". These new xenobots can then search for cells and create their own copies. Again and again.
Joshua Bongard, PhD, a computer scientist and robotics expert at the University of Vermont who led the new study, said: "With the right design, they will spontaneously self-replicate".
In the frog Xenopus laevis, these embryonic cells develop into skin. "They would sit on the outside of the tadpole, preventing pathogens from entering and redistributing mucus," said Michael Levin, PhD, professor of biology, director of the Allen Discovery Center at Tufts University and co-leader of the new study.
"But we are placing them in a new context. We are giving them the chance to rethink their multicellularity," the professor noted. "People have thought for quite a long time that they had developed all the ways life can reproduce. But this is something never observed before," said Douglas Blackiston, PhD, senior scientist at Tufts University and the Wyss Institute, who created the xenobot "parents" and developed the biological part of the new study.
“This is profound. These cells have the frog's genome, but without turning into tadpoles, they use their collective intelligence and plasticity to do something remarkable. We have a fully unchanged frog genome, but it gives no hint that these cells could work together on this new task of gathering separated cells and then compressing them into working self-copies”
In earlier experiments, scientists were amazed that xenobots could be designed to solve simple tasks. Now they are astonished that these biological objects, a computer-designed collection of cells, will spontaneously reproduce.
Sam Kriegman, PhD and lead author of the new study, said: "These are frog cells that replicate in a way that is very different from how frogs do it. No animal or plant known to science reproduces this way."
The parent xenobot, a sphere made of roughly 3,000 cells, is itself formed into a sphere. Kriegman explained: "Children can be born from them, but after that the system usually dies out. It is actually very hard to get a system to keep reproducing."
But with the help of an artificial intelligence program running on the Deep Green supercomputer cluster at the Advanced Computing Core at UVM in Vermont, an evolutionary algorithm was able to test billions of body shapes in simulation, including triangles, squares, pyramids and starfish, to find those that made cells more efficient at "kinematic" replication based on movement.
“We asked the supercomputer at UVM to work out how to adjust the shape of the original parents, and after several months of work the AI came up with some strange designs, including one that resembled Pac-Man. It looks very simple, but a human engineer would never have come up with it. Why one tiny mouth? Why not five? We sent the results to Douglas, and he created these Pac-Man-shaped parent xenobots. Then these parents created children, who created grandchildren, who created great-grandchildren, who created great-great-grandchildren”
Kinematic replication is well known at the molecular level, but has never before been observed at the scale of whole cells or organisms. Bongard said: "We discovered that there is this previously unknown space within organisms or living systems, and it is a huge space. So how do we explore this space? We found xenobots that walk. We found swimming xenobots. And now, in this study, we have discovered xenobots that reproduce kinematically. What else is there?".
“We are working to understand this property, replication. The world and technology are changing rapidly. It is important for society as a whole that we study and understand how this works. These millimeter-sized living machines, fully contained in a lab, easily shut down and vetted by federal, state and institutional ethics experts, do not keep me up at night. The risks are the next pandemic, accelerating ecosystem damage from pollution, and growing threats linked to climate change. This is an ideal system for studying self-replicating systems. We have a moral duty to understand the conditions under which we can control, guide, suppress and amplify this”
According to the researchers, it is necessary to create technological solutions that grow at the same pace as the problems the world faces. The team sees promising advances in regenerative medicine from this research.
“If we knew how to tell collections of cells to do what we want, we would ultimately have regenerative medicine, a solution to traumatic injuries, birth defects, cancer and aging. All these different problems exist because we do not know how to predict and control which groups of cells will build what. Xenobots are a new platform for learning”
