A salamander loses its leg to a predator. Within weeks, a perfect replacement grows back—complete with bones, muscles, nerves, and skin, all in exactly the right places. Meanwhile, a human child who loses a fingertip might regenerate it, but an adult who suffers the same injury will only form a scar. What does the salamander know that we've forgotten?

The answer might be written in electricity.

The Body Electric

Every cell in your body is electric. Not just your neurons firing thoughts or your heart muscle beating—every single cell maintains a voltage across its membrane, like a tiny battery. Bacteria discovered this trick billions of years ago, long before brains existed. Even bacterial biofilms use electrical signals to coordinate their behavior.

This isn't the electricity of power lines or lightning bolts. It's subtler: ions flowing through channels in cell membranes, creating voltage differences measured in millivolts. But these whisper-quiet signals carry profound information. They help determine whether a cell becomes skin or nerve, whether it divides or stays put, and crucially, whether a missing body part regenerates or scars over.

Michael Levin, a biologist at Tufts University, has spent decades decoding these electrical signals. His work suggests something radical: bioelectricity functions as a control system for anatomy, a layer of biological software running on cellular hardware. While DNA provides the parts list—the proteins—bioelectric patterns tell cells where to go and what to build.

"DNA doesn't encode geometry," Levin explains. Your genome contains instructions for making proteins, but nowhere does it specify that your heart goes on the left or that you have five fingers. That information exists elsewhere, written in electrical gradients that span cells, tissues, and entire body regions.

Cracking the Voltage Code

Levin's team discovered that specific voltage ranges correspond to specific body structures. In frog embryos, a narrow band of electrical potential marks where eyes should form. By artificially setting cells to this "eye voltage"—even in completely wrong locations like the tail or gut—the researchers triggered eye formation in those aberrant spots.

Think about that for a moment. Cells that would normally become tail tissue instead organized themselves into functional eyes, complete with lenses and light-sensitive cells, simply because they received the right electrical signal. The tissue lineage didn't matter. The voltage did.

This suggests that bioelectric patterns store what Levin calls "pattern memories"—encoded information about target shapes that cells collectively navigate toward. It's not unlike how a thermostat maintains room temperature by constantly comparing actual temperature to a set point. Cells compare their current arrangement to an electrically encoded target morphology and adjust accordingly.

The evidence for this appears in unexpected places. When researchers created "Picasso tadpoles" with eyes, nostrils, and other facial features scrambled into wrong positions, something remarkable happened during metamorphosis. The organs moved in novel ways to achieve a normal frog face. The system knew what a proper frog face should look like and corrected toward that target, even from a starting point it had never encountered in evolution.

The Regeneration Switch

Some animals never lost this electrical mastery. Planarian flatworms can rebuild any missing body part, including their heads. Axolotl salamanders regenerate eyes, limbs, tails, jaws, and even portions of brain. The secret lies partly in their bioelectric signaling.

In planarians, the voltage at a wound site determines what grows back. Depolarized voltage (less negative) triggers tail formation. Hyperpolarized voltage (more negative) triggers head formation. By manipulating ion flows with drugs or genetic tools, researchers can override these signals—creating two-headed worms or worms with tails at both ends.

Tadpoles offer another striking example. Young tadpoles regenerate lost tails perfectly, but older tadpoles lose this ability during a "refractory period." Levin's team found they could restart regeneration during this period by triggering specific ion flows—proton pumping or sodium influx. The result: complete tail regrowth including spinal cord, muscle, blood vessels, and nerves.

The bioelectric signal acts like a master switch, activating a coordinated regeneration program. It doesn't micromanage every cell. Instead, it sets a goal state that the cellular collective then works to achieve.

Beyond Emergence

This challenges how most biologists think about development. The mainstream view holds that body patterns emerge through local interactions between cells, like sand dunes emerging from wind and gravity. No blueprint exists; the pattern just happens.

Levin argues this misses something crucial. Yes, local interactions matter, but they're guided by stored information about target anatomies. When a deer damages its antler, the injury location is "remembered" and appears as an extra branch point when the antler regenerates the following year—months later and after the original antler has fallen off entirely. Something stores spatial information across time and distance.

This isn't mysticism. It's control theory applied to biology. The body operates as a closed-loop homeostatic system, constantly minimizing the difference between current shape and target shape. Just as your body maintains temperature and blood sugar through feedback loops, it appears to maintain anatomical structure through bioelectric feedback.

The Medical Frontier

Understanding this electrical code could transform medicine. In the United States alone, over 104,000 people wait for organ transplants. Seventeen die each day before an organ becomes available. What if we could coax the body to regenerate its own replacement parts?

We're not there yet, but the path is becoming clearer. The field of "electroceuticals"—therapeutic applications of bioelectricity—is expanding beyond pacemakers and nerve stimulation. Researchers are exploring how bioelectric manipulation might address birth defects, traumatic injuries, degenerative diseases, aging, and even cancer.

Cancer particularly interests bioelectricity researchers. Tumors show abnormal electrical properties compared to healthy tissue. Levin's work suggests that bioelectric signals help suppress tumor formation, and disrupting these signals can trigger cancerous transformation even without genetic mutations. Conversely, normalizing bioelectric patterns in genetically damaged cells can prevent tumor formation.

The implications extend to regenerative medicine more broadly. Rather than fighting the body's tendency to scar, we might reprogram cells electrically to enter regeneration mode. Rather than transplanting organs, we might provide the bioelectric instructions for growing new ones.

Software and Hardware

Levin uses a computer analogy that clarifies why this matters. Traditional molecular medicine—gene therapy, CRISPR, targeted drugs—works at the hardware level. It's like fixing a computer by replacing transistors or rewiring circuits. Bioelectric medicine works at the software level. It reprograms what cells do without changing what cells are.

This offers advantages. Software changes are faster and more flexible than hardware changes. You can run different programs on the same hardware. A cell with a given genome might become part of an eye or part of a tail depending on the bioelectric signals it receives. The hardware stays the same; the software differs.

This also means bioelectric interventions might be temporary. Flip the right electrical switches at the right moment, and cells may reorganize into a new stable pattern that persists even after the electrical signal stops. The tadpole tail regeneration experiments demonstrated this: a brief electrical stimulus triggered regeneration that continued to completion without further intervention.

Tools of the Trade

Recent technological advances make studying bioelectricity possible in ways it wasn't a generation ago. Voltage-sensitive dyes let researchers visualize electrical patterns in living embryos, watching in real time as voltages shift during development. Optogenetic tools allow precise control of ion channels using light, enabling researchers to rewrite bioelectric patterns with spatial and temporal precision.

Genetic techniques reveal which ion channels and pumps matter for specific processes. The cast of characters includes potassium channels, sodium pumps, proton pumps, calcium channels, chloride transporters, and gap junctions that electrically couple neighboring cells. Each contributes to the overall bioelectric landscape.

Pharmacological tools—drugs that open or close specific channels—provide another handle on the system. Some are already FDA-approved for other uses, potentially speeding translation to medical applications. Others are being developed specifically for bioelectric manipulation.

The convergence of these tools with computational modeling is crucial. Bioelectric patterns are complex, involving thousands or millions of cells with different voltages connected through gap junctions into networks. Understanding how these networks store and process information requires both experimental data and theoretical frameworks.

The Collective Intelligence

Perhaps the most profound aspect of Levin's work is his framing of multicellular organisms as "collective intelligences." Individual cells are agents with limited perspectives and capabilities. But connected through bioelectric networks, they form a collective that can pursue goals—like achieving a target anatomy—that no individual cell understands.

This mirrors how neurons in your brain collectively produce thoughts and consciousness that no single neuron possesses. Levin suggests morphogenesis—the creation of body form—is the behavior of a collective cellular intelligence, with bioelectricity as its computational medium.

This perspective opens new questions. If cellular collectives can store pattern memories and navigate toward target morphologies, what else might they be capable of? Can we communicate with them more directly, providing new target patterns for them to build? Can we enhance their problem-solving abilities, helping them regenerate structures they normally couldn't?

Looking Forward

Levin believes we'll see major bioelectric regenerative medicine breakthroughs within his lifetime. The science is advancing rapidly. The theoretical framework is maturing. The tools are improving. What once seemed like science fiction—regrowing limbs, preventing birth defects through bioelectric modulation, electrically reprogramming tumors into normal tissue—now appears as engineering challenges rather than impossibilities.

"Anything not forbidden by the laws of physics we ought to be able to do functionally," Levin argues. Physics doesn't forbid human limb regeneration; salamanders prove it's possible with the right biological software. The question is whether we can learn to write that software ourselves.

The path forward involves mapping the bioelectric code more completely—identifying which voltage patterns correspond to which anatomical structures across different organisms and developmental stages. It requires understanding how bioelectric patterns interact with genetic and biochemical signals in integrated control systems. And it demands translating lab discoveries into safe, effective medical interventions.

The salamander's secret is becoming less mysterious. Written in the subtle language of cellular voltages, instructions for regeneration persist in organisms that never lost the ability to read them. The challenge now is learning that language ourselves—teaching human cells to remember what they once knew about rebuilding what's been lost.