Cooperative Cellular Societies
Thursday, August 22
Good morning.
Athena Aktipis’ The Cheating Cell is a book about the evolutionary history of cancer — as such, it’s largely concerned with when and why individual cells defect against their neighbors.
But there’s something I really liked about the way she describes what is happening the other 99.9% of the time: intercellular cooperation.
You might feel like a unitary being, but in reality you are made of trillions of cells that are cooperating and coordinating their behavior every millisecond to make you a functional human being. The number of cells inside our bodies is mind-boggling—more than four thousand times the number of humans on Earth. We are thirty trillion cooperating, evolving, consuming, computing, gene-expressing, protein-producing cells. The body is literally a world unto itself. Each of these cells is like a little homunculus inside you, taking information from its environment, processing that information using complex genetic networks, and changing what it does in response to those inputs. Each cell has its own set of genes, unique gene expression (i.e., the specific proteins the cell is making) and its own physiology and behavior. The cooperation happening inside us is quite astounding. How can thirty trillion cells make a being that seems so much like one single entity with one set of goals? How can I be made of so many cells yet feel so unitary?
One answer to these questions comes from evolutionary biology: We act and feel like unitary organisms because evolution has shaped us to be cooperative cellular societies. Perhaps we feel like unitary beings because evolution has fashioned us to act as though we are. We have been shaped by nearly one billion years of evolution on multicellular bodies to have cells that act in a way that enhances the survival and reproduction of the cooperative cellular society as a whole—the multicellular body. Our cells constrain their proliferation, divide labor, regulate their resource use, and even commit cell suicide for the benefit of the organism. The scope of cooperation inside us is beyond anything humans have ever accomplished—the cells inside us behave like a success story of a utopia, sharing resources, taking care of the shared environment, and regulating their behavior for the good of the body.
Among the many things I am totally dependent on, the evolved selflessness of the trillions of cellular subcomponents in my body's machinery is one that I don’t recognize very often.
Actually, that’s an overstatement. I’ve never genuinely stopped and appreciated it until this moment.
To the extent that “I” am something above and beyond these citizens of my body, I owe my existence to their labor, and their restraint.