Every Single Cell in Your Body Could Be Conscious, Scientists Say. That Could Rewrite Everything We Know About Human Evolution (2024)

BEFORE YOU BECAME YOU, your entire being was wrapped up in just two cells: your mother’s egg and your father’s sperm. Yet the dance between these two resulted in an embryo, a ball of cells that differentiated into specialized cells that would grow to become your heart, your gut, your fingers, and all your other parts. The cells of your developing embryo constantly communicated with each other, including through a sense of touch, in part by extending tendrils to detect the cells around them. Your body’s cells perform incredible feats of communication and cooperation like this right from the start.

The reason for such cooperation comes down to a cellular form of intelligence, says evolutionary biologist and physician William B. Miller, Ph.D. He’s co-author of the book, The Sentient Cell: The Cellular Foundations of Consciousness, published in January 2024, which proposes a radical new way of thinking about some of life’s tiniest components.

Miller is among a small but growing group of scientists who believe we should no longer think of cells as passive robots that automatically follow a code of instructions, carrying out orders from our genome like mindless drones. Instead, they say, the roughly 37 trillion cells that make up our own bodies are conscious—and that life and consciousness began at the same time.

It’s a revolutionary idea, Miller tells Popular Mechanics, but assuming cells have a form of consciousness can give us a better understanding of complex processes. These include cellular communication and decision-making, and even the motivation behind an embryonic cell specializing into a specific organ. While it’s not widely accepted among scientists, this concept of “existential consciousness” will profoundly transform the way we approach cellular bioengineering problems like tissue regeneration, provide a different perspective on finding cures for diseases like cancer, and even help us survive on Mars, Miller says.

From early in life’s history, cells of all kinds have combined their skills to further a common goal—to keep on living and reproducing. “Cells have formed colonies. It’s very much like a city that we humans might engineer. It has nutrient channels, an outside and an inside, a collective metabolism,” Miller says. For example, microbes collaborate with each other. They’re codependent, trading resources as well as competing. “In order to make this ecology flourish, each of these cells is taking intelligent action. They’re communicating with one another, and both individually and collectively deploying resources. That’s problem solving and decision making. That’s cognitive action, and it’s one element of consciousness,” he says.

It’s still a hard concept to swallow—that bacteria and other microorganisms are conscious on any level. To animals like us, consciousness is due to a complex nervous system.

However, Miller and his fellow authors see this higher, human form of consciousness as a natural property our cells create—together with the more than 10 trillion essential microbes that are a part of our bodies. “Every aspect of the consciousness that I’m experiencing is a simultaneous aggregation of the consciousnesses of all of my body cells and all of those microbes working in tandem, coordinating so seamlessly that I feel like I’m one individual,” he says.

Before exploring that idea further, it’s important to understand one thing: We are holobionts, because we consist of our own host cells and the ones we live with in symbiosis, or mutual cooperation. In particular, we live in symbiosis with a bacterial, viral, and fungal population of cells. In other words, our cells and our microbes mutually benefit one another.

The evolutionary science of the hologenome—that we co-evolved with our microbiome—says that evolution led those first cells to continue forming different kinds of habitats in order to survive and thrive; hence, the development of plants, animals, and fungi. “We’re a constellation of habitats,” says Miller, who spent decades studying the human microbiome and has written several books on the hologenome. He compares human bodies to a successful engineering project for ever more complex groupings of diverse cells living together and adapting to changing environments over millions of years. A form of cellular consciousness has been with us since life first emerged, 3.5 billion years ago. They were able to multiply into abundant varieties of bacteria, amoeba, and then more complex organisms because of their particular awareness. Today, your brain, microbiome and the cells of your gut work together as a community of cells to create your sense of consciousness.

“We are a rich, wonderful, delightful environment for cells,” he says. “So, we bear a resemblance to the first biofilm [microbial colony]. …We are one end result, along with every other creature that can be seen—we are a particular solution to a set of biological cellular problems.”

HOWEVER, NOT ALL SCIENTISTS who study the biology of life are convinced that cells are conscious. Cells respond to both chemical and physical signals, including pressure from surrounding cells. The cells of a developing embryo know, for example, when their number has grown to 400. At this exact point, the group begins to separate into three axes that determine the body’s final orientation: front and back, left and right, up and down. They know how to differentiate themselves into the tissues that will become your organs and other parts. Cells are the architects of the organism, cell biologist Alfonso Martínez Arias, Ph.D., tells Popular Mechanics.

His work shows that a person’s genome is a toolbox for the cell to use as it may. Yet we cannot presume that a cell’s behavior is due to consciousness, says Martínez Arias, who spent 40 years at the University of Cambridge researching how a fertilized egg can become an individual with billions of specialized cells.

While cells exhibit behaviors that you could call a sort of intelligence—responding to other cells and their environment—the crux of the problem is that it’s hard to define consciousness, he says. “With cells, there is some kind of computation going on, with an output that can be predicted. …I think increasingly, there is evidence that cells have capacities that are not encoded in the genome.” For instance, the ability to pick and choose from the toolbox of genes that give us our ultimate characteristics. Through experiments, researchers have been able to study cell responses to different chemical and physical stimuli, such as exposing them to a chemical compound that would cause the cells to produce a different compound. “So we are able to communicate with them, but we do it badly. …But I think we are learning their alphabet, we’re learning their language,” Martínez Arias says. He hopes that continuing such investigations will lead us someday to knowing what makes cells tick.

Conventional resistance to labeling cells as “conscious” comes from defining consciousness from a human point of view, Miller believes. We compare our own consciousness to the capacity of other animals, such as the mosquito or the lion. “And the more you look, the more you realize that our form of consciousness, with its own intelligence, is different from other animals, [so our view is skewed].” A cell’s consciousness is more elemental, a simpler form of cognition, he says.

Here’s a practical reason to treat cells as conscious, Miller says: Once we realize that cells are “creative and intelligent problem-solving materials,” we can treat them as partners in designing better biomedical therapies and solutions. By studying their motivations and decision-making, we’ll find more ways to manipulate cells, such as interrupting their processes. For example, cancer cells communicate with each other and with non-cancer cells in the body. We are finding promising cures for some cancers that break down the communication cancer cells use in their efforts to propagate and form tumors. This type of directed immunotherapy leaves patients’ own healthy cells undamaged, unlike chemotherapy, or radiation, which damages healthy cells too.

We’re already taking advantage of cell behavior to engineer microbes that eat plastic. Such creative solutions in the future won’t be possible if we treat cells as robots without preferences, Miller says. We’ll even understand how to explore space better. For example, the radiation levels on a journey to Mars are too high to survive. One of the solutions could be figuring out a way to strengthen our cells against dangerous radiation. Miller believes a study of how cells themselves could engineer an adaptation to radiation would help.