Brinedew

Unpublished draft

Defensive sabotage is not friendly fire

I.

If you spend enough time reading about biology, you will eventually notice that everyone’s understanding of why bodies break down progresses through the exact same three-stage meme format.

At the left end of the bell curve is the Naive View of Aging: everything is wear and tear. A body is like a 1998 Honda Civic. You drive it long enough, the brake pads wear thin, the timing belt snaps, the gears grind down, and eventually the whole thing rusts. In this model, old bodies are frail for purely entropic reasons. Your joints hurt because the cartilage has literally rubbed away; your skin wrinkles because the elastic proteins got stretched out too many times.

In the middle of the bell curve is the Midwit View of Aging, usually adopted by medical students in their second year. The midwit realizes that biology is actually perfectly capable of reversing entropy when it wants to. You aren’t a Honda Civic; a Civic can’t spontaneously heal a dent in its fender, nor does it replicate itself every few decades.

The midwit replaces the “wear and tear” model with two slightly more sophisticated causal mechanisms.

The first is injury. The body is constantly under assault by pathogens, radiation, and toxins. It does its best to repair the damage, but sometimes the repair leaves a scar.

The second is antagonistic pleiotropy. Evolution is a blind, idiot tinkerer. It selects for traits that help you survive long enough to have children, and it absolutely does not care what happens to you after that. If a gene makes your immune system hyper-aggressive—ensuring you survive the plague at age 20, but guaranteeing you develop crippling rheumatoid arthritis at age 65—evolution considers that a fantastic trade. Your immune system attacking your own joints is “friendly fire.” The artillery was aiming at a streptococcus bacterium, but somebody input the wrong coordinates, and now your cartilage is collateral damage.

Both of these models are very useful. They map well onto a lot of human pathology. But they are missing a third category, one that is vitally important if we actually want to fix things.

II.

Suppose a major strategic bridge collapses in your country during a war. You are the general in charge of logistics, and you demand to know why the bridge fell. There are three very different causal models for what just happened:

  1. Enemy Action: The invading army sent bombers to blow up the bridge.
  2. Friendly Fire: Our own artillery was shelling an enemy battalion near the river, missed, and accidentally took out the bridge.
  3. Defensive Sabotage: The enemy was advancing rapidly toward the capital. Our local commander realized they were about to cross the river, so he intentionally rigged the bridge with dynamite and blew it up to stop them.

Why does it matter which model is true? Because your job is to figure out how to prevent bridges from falling in the future. And your choice of intervention depends entirely on the causal model.

If the bridge fell due to Enemy Action, the correct intervention is bridge hardening. You build the next bridge out of reinforced concrete, you put anti-aircraft guns on the towers, and you make it indestructible.

If the bridge fell due to Friendly Fire, bridge hardening still sort of works, but the better intervention is improving targeting. You train your artillery crews better, or maybe you tell them to stop shooting so close to your own infrastructure.

But if the bridge fell due to Defensive Sabotage, bridge hardening is absolutely catastrophic.

Imagine you spend billions of dollars researching an unbreakable, ultra-hardened titanium bridge. You install it over the river. The enemy advances, the local commander panics and pushes the detonator—and nothing happens. The dynamite goes off, but the titanium bridge stands strong. The enemy rolls their tanks across your beautiful, indestructible bridge and burns your capital to the ground.

So you find yourself stuck in a lose-lose double bind. Harden the bridges, and lose to invaders who cross them. Or let the bridges fall, and watch as the country’s infrastructure deteriorates to the point of being unlivable.

III.

Consider the lizard.

If you grab a lizard by the tail, the tail will snap off in your hand. The lizard will scurry away into the underbrush, leaving you holding a twitching piece of meat.

If you are operating under the Naive View, you might think: “Wow, biological materials are so flimsy! Pure wear and tear. The mechanical stress of my hand was too much for the poor lizard’s tensile strength.”

If you are operating under the Midwit View, you might think: “Ah, friendly fire. The lizard’s muscles spasmed so hard in a panic that it accidentally tore its own spine apart. Evolution is so sloppy.”

But if you actually look at the anatomy of a lizard’s tail, you will find something incredible. Lizards have specialized fracture planes built into their vertebrae. They have complex sphincter muscles inside the tail designed to immediately clamp down and prevent blood loss the second the tail detaches. The tail breaking isn’t an accident. It is autotomy. It is Defensive Sabotage.

The easy breaking is the point.

Now imagine a well-meaning bio-hacker decides to “cure” the lizard’s fragile tail. He gene-edits the lizard so that its cartilage is reinforced with carbon nanotubes. The tail is now indestructible. The lizard goes out into the wild, a hawk swoops down and grabs it by the tail, the lizard tries to drop the tail… and fails. The hawk carries the lizard away and eats it.

The intervention was counterproductive because the bio-hacker mistook defensive sabotage for friendly fire.