The crescent-shaped balls of cells would travel in circles, piling up cells that could grow into mobile clusters.
Scientists on Monday announced that they had improved a way of getting mobile clusters of cells to organize other cells into smaller clusters that could be mobile themselves. The process of copying is called "kinematic self-replication," but it's not entirely correct that the copies need help from humans to start moving on their own, and that the copying process grinds to a halt after just a couple of cycles.
CNN said that the world's first living robots can now reproduce.
The scientists and some of the coverage of the developments are promoting something that is more interesting than it is. Let's take a look at what's been done.
There are balls of cells.
The process begins with isolating the frog's egg. Two of the cells' interesting properties are relevant for this work. The cells stick to each other. If you leave a group of them in a culture dish, they will pull together into a ball. You can leave a collection of them in culture, and they will stick together and form a ball of cells.
The cells' second feature is that they will self-organize, which means that the external cells have thread-like projections. These spin around in circles, pushing against the culture medium. Eventually, the entire ball of cells will end up spinning its cilia in sync, as neighboring cells coordinate their cilia.
For simplicity, we're going to call these mobile balls of cells, or MBCs. An MBC can trace a circular path in the culture dish without obstacles for up to two weeks before running out of energy. The CNN title is "living robots". The research team described them in a paper back in March.
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The researchers put a collection of cells in the dish with the MBCs. As the MBCs spun around in circles, they created a cluster of cells at the center of the circle they traced. A new cluster would start to form from the loose cells.
The new clusters were too small to do much. They could be pulled out of the dish and put in a new one with more cells. The small clusters would grow by incorporating some of the additional cells and eventually reach the point where they would be mobile.
Too small.
The process is inefficient. The first generation of MBCs was larger than the second. You could go two generations of MBCs before the process stopped. These replicators are not very efficient.
The new work looked at ways to change the shape of the original MBCs. It takes a few weeks in culture dishes to see how an MBC behaves after being modified. Being inherently lazy, the researchers decided to model their behavior using computers, implementing an evolutionary algorithm that created variations of shapes that were then tested for their ability to herd cells.
A researcher in the Department of Computer Science told CNN that the combination of modeling and an artificial intelligence is an artificial intelligence. If scientists give the public accurate information, it will help them to understand what they're doing better.
The most effective MBCs are those that start with a large amount of cells. The model came up with a solution that was a half-toroid.
The researchers had to perform surgery on MBCs, cutting out a notch on one side of the ball after it was flattened into a disk, and then unflattening it. Some of the crescent-shaped MBCs could produce offspring that could go for three generations before the process failed. This wasn't self-replication since the generations wouldn't assume a crescent shape without intervention.
