When Tufts University researcher Michael Levin started working with frog skin cells, it took him in unexpected directions. Terming his creations “xenobots,” he describes them as simultaneously animal, machine, and robot. Recently, his understanding of xenobots became much more complicated when he discovered that the tiny creatures can replicate, or make copies of themselves.

“It’s never been seen on Earth before,” Levin said.

A Russian Jewish immigrant who lives on the North Shore, Levin is now fielding emails from the public since the discovery. In the past, he has been profiled in The New Yorker and The New York Times.

“Some people are absolutely terrified, which is completely misplaced,” he said. “If you want to be worried about something of that nature, there are natural and artificial pandemics, bacteria and viruses … We already have all of those things.” In contrast, he said, “I’m experimenting with frog skin in a petri dish.”

“One thing about xenobots,” he said, “is that they point out deficiencies in lots of terms. Robots, machines, organisms – we used to think there were strict differences. There are not deep differences. They are arbitrary things … Now we have something like the xenobots. It’s completely unclear where it lands in that terminology.”

The xenobots are a combined effort between Tufts, the Wyss Institute at Harvard – where Levin holds a joint appointment – and the University of Vermont. In a separate interview, UVM researcher Josh Bongard recalled finding out that the xenobots were replicating.

“It’s definitely a first,” Bongard said. “We knew this could happen, but not to this degree.”

Less than a millimeter in diameter – barely visible to the human eye – each xenobot was released into a petri dish with water and single frog cells. The xenobots worked like small bulldozers to push the frog cells into piles. The cells within the piles began sticking to each other. Soon, the piles grew small hairs called cilia, which the xenobots moved like oars in the water. By the time four days had passed, the piles had become child xenobots. Their normal lifespan is 10 days, although this can be extended to as much as 80.

Bongard noted that replication is different from reproduction. A computer virus will self-replicate, for example, whereas a plant or animal will reproduce. A plant will release seeds outside itself, while a mammal will grow offspring inside itself.

“I think what’s really useful here is not the replicating itself,” said Levine. “What the replicating is telling us is what this thing can do. We could work with that.

“It’s not just me and Josh. It’s us combined with the xenobots … The frog cells have an intelligence. It will enable us to do amazing things.”

“Frog cells are perfectly happy in fresh water,” Bongard pointed out. “We can create xenobots that pull microplastics out of wastewater, detect contaminated soils, [work in] sewer systems, water filtration plants, submarine engine inspection.” He said that xenobots are “like the computer in the 1940s.”

Most significantly, he said, they are a “new way to investigate living systems, how things work. It lays out the potential for new growth in cancer, aging, regenerating eyes or limbs.”

Levin marveled that some members of the public are so excited about the medical possibilities of xenobots that they want him to work faster.

“People have a lot of unmet biometric needs,” he said, “all kinds of disorders, spinal cord injuries, birth defects, trauma, cancer. People see this advance and say, ‘Fine, what does it mean to me?’ … A lot of them ask, ‘What’s taking you so long? I need new eyes, a spinal cord, my kid needs a new finger.’”

Levin said he understands the potential spiritual ramifications of the discovery that xenobots can replicate. He recently spoke with several rabbis on the subject.

“I definitely think there’s a spiritual dimension to all this,” he said. “The whole business of naming the animals [by Adam in the Garden of Eden], I take it very seriously. I think what we’re doing in a spiritual sense is not just assigning names in an everyday sense, but understanding their inner nature. I think that’s what’s going on here.”

The researchers noted that they are proceeding with caution in other ways.

“We understand [some] people are apprehensive,” Bongard said. “We’ve had some discussions with the [Food and Drug Administration]. We’re trying to invite them into the conversation. We’re at the very early stages of the talks.”

“I think, really, our job as scientists is to communicate as clearly as possible with the public about the role of the scientific process,” Levin said. “To address the increasing needs that humanity has, in terms of human and animal suffering, in terms of the environment, various medical disparities. The answer to all of this is more science, not less science.”