It happens when you hit the tip of your index finger hard with a hammer. It hurts like hell immediately, of course, and you know you’re in for trouble. Then it turns red and begins pulsating. The nail quickly gets discolored as blood seeps under it. And it hurts for days.
Within a week or so the pain mostly disappears, but the nail color goes blueish purple. The blood continues to drift under the nail until it reaches the front edge. It dawns on you, vividly: “I’m gonna lose that nail.”
That realization is accompanied by remembering that fingernails grow back. After several months, a new nail begins growing and pushing the damaged nail out of the way. Imagine if other parts of your body could regenerate like that.
All our cells are constantly growing, of course. Liver cells divide; old ones die and are replaced. This is also true of skin cells. Did you know that much of the dust in your house is discarded dead skin cells?
Living organisms repair themselves when possible. Starfish are famous for growing new “legs” and crabs can regenerate their claws. The code that allows the regeneration of major body parts possible is genetic, but not yet fully understood. If we can reverse-engineer it, the tangible results of cracking that code may be in humanity’s healthcare future.
The secret to the regeneration of fingernails is the presence of a root, technically called a nail matrix, a small, specialized organ located under the cuticle that creates keratin using stem cells. Just as hair, keratin, is made of cells, so too are fingernails, products of the root. Keratin is composed of hardened epithelial cells (skin) stacked tightly in layers, and no, despite the rumors otherwise, it does not continue to grow after we die.
The heart has no root or matrix, nor do the kidneys. Of our major internal organs, only the liver can regenerate its damaged parts. The self-maintenance code inside of every cell has limits, and when those limits are exceeded, regeneration and repair become unstable. An inherent biological indeterminacy at the sub-atomic level enables genetic freedom, leading to both healthy and unhealthy mutation; when unhealthy, we call it cancer.
We are not coded for immortality. To the contrary, we are coded for death. The trajectory of our species mirrors the replacement and repair coding of cells; older cells die to provide for the arrival of newer cells, ones potentially better adapted to changing conditions. And so, too, individual organisms die and are replaced. The dynamic indeterminacy of an organism buttresses the duration of a species as each successive generation offers the potential of being better suited to an ever changing environment. Life forms evolve in tandem with the evolution of the planet and the universe overall. Even stars age and die, their remaining parts becoming new matter, matter like you.
Human dreams of immortality are seductive, even more so given our lived experience of regeneration and repair. As we age, however, our bodies gradually lose their capacity for repair and we begin to suffer. Organ damage accumulates, bones become brittle, joints wear out and we experience increased pain. Blessedly, relief comes to all of us at the end. Death is impartial and mercifully calms all suffering.
To nail it: I’m not saying death is a friend, but neither is it an enemy.
