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The true meaning of cell life and death

Two hundred years ago, William Lawrence blew the roof off the Hunter Lecture Series at the Royal College of Surgeons by adding the word “biology” to the English language to discuss living physiology, behavior, and diversity as a matter of gunky chemistry and physics, sans super-added forces. Moving on from there, one might think that life can arise from non-living stuff any time, or whenever the parameters are right, and who’s to say whether that’s a rare or common thing. Therefore it was difficult on the basis of logic alone to conclude the reverse, that the living things we see are a matter of living things’ reproduction and nothing but.

The following decades produced a new level of microscope technology, knowledge of sperm and ova as cells, the germ theory of disease, and ultimately, cell theory. The names are well-known, like Schleiden, Virchow, Schwann, Weisman, and Pasteur, as well as Thomas Huxley’s “On the Physical Basis of Life.” Crucially, cell theory is composed of three independent statements:

  • The cell is the smallest living unit: this means no component of a cell is itself alive. (Cells can be of different sizes, so don’t crack wise about mitochondria.)
  • Life is cellular: This is simply an observation, that we see no other kind of life around here.
  • Cells are produced (“arise from”) by living cells: This is an inference based on observed homology, that despite other differences, the fundamentals of all cells are the same.

The necessary conclusion is that your life, and that of any multi-celled organism, isn’t life at all. “You” as a being, your identity and experience, is something that a bunch of physically clumped-up living cells do. Regarding its end, your death (nothing personal), isn’t a whole lot of actual death at all–not of the living things. It’s the cessation of that thing they’re doing. You knew this already, what with The Immortal Life of Henrietta Lacks and related writings, right?

Life yes, person no.

We don’t even have to wait for that grim moment to see that every day tons of your cells die while you continue onward, such that your cellular composition is best understood as a wave-front, undergoing constant replacement at a rate specific to each tissue. Conversely, and consistently, when you die, most of your cells don’t. I mean, they will eventually, but the point is that they don’t have to.

What is that end, anyway? It’s tempting to consider apoptosis, programmed cell death, as the model. A cell expels some of its contents, dismantles others, and ultimately simply comes apart. It’s a sweet, quiet, reassuring, purposeful-seeming death. It happens all the time, especially in producing various gaps or separated spaces of your own body during embryonic development. It is nice to think of organismal, you-death, as a great big cooperative and purposeful and “programmed” macro-version of apoptosis. The trouble is that it’s wrong. Not one death of a human being or anything else you’re familiar with is caused by mass apoptosis. Mechanically speaking, we die because some piece is too damaged to connect with the others, due either to injury or senescence. It’s all killing. There is no “it was just his time to go.”

Image credit: Photograph of a burial vault built circa 1890 to protect against premature burial, originally published in Popular Mechanics Magazine, 1921. Public Domain via Wikimedia Commons.

Just in case that’s not gothic enough for you … no one waits until every one of the cells which used to comprise you is dead, before announcing you dead. The decision isn’t physiological at all; it’s social–the point at which everyone is pretty much agreed that remaining living cells aren’t going to do the “you” activity any more. Obviously when this is shifts with technological methods to prompt them to do just that; the insight is that this point is based on everyone else’s needs and views, and nothing to do with your “spark of life” (or whatever you want to call it) in any cells.

Old-school horror: In older cemeteries it’s not unknown to find the occasional remains of a person in a posture suggesting that he or she had been so adjudged sooner than we’d like to acknowledge.

The people who built the above were very considerate. But you might consider how much of what they had to observe before someone said, “Hey, maybe we better include escape hatches.”

New-school horror: There is no more thoroughly dead person than the guy who paid umpty-ump thousands of bucks to be cryogenically preserved, meaning, killed deader than a door nail via rupturing every last cell simultaneously.

It makes bottled tap water look positively honest.

Your life isn’t really being alive, and your death isn’t really being dead. The absence of useful terminology to express this in ordinary speech is one of professional biology’s greatest intellectual failings, and the absence of this point from biology texts is one of its pedagogical failings. It might have seemed 200 years ago that nailing down what “life” is would also tell us who we are. But it doesn’t.

The content of this post was originally published as a 3-part series on the author’s personal blog: Part One: Death: When and Who; Part Two: Death: How and Why; Part Three: Death: What Remains.

Feature Image: Anitschkow Myocytes in an Aschoff Body, Rheumatic Myocarditis by Ed Uthman, MD. CC BY-SA 2.0 via Wikimedia Commons.

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