You are filled with bacteria, and you are covered in them. And a whole lot of them are just waiting for you to drop dead.
As soon as you die, they’ll swoop in. This week, we learned exactly how microbes chow down on us. A brave and strong-stomached team of scientists spent months watching dead bodies decompose, tracking all the bacteria, fungi, and worms, day by day. Forensic scientists can use this timeline, published in Science, to help determine time—and even place—of death. (More on that in a previous Gory Details.)
The microbes in your intestines get first dibs, the scientists found. As soon as you die, they’ll start decomposing you from the inside out. Meanwhile, other bacteria on your skin or in the soil beneath you start mounting an attack from the outside in. As Michael Byrne at Motherboard so nicely summed it up, “Earth is just waiting for you to drop dead.”
That’s a little unsettling, if you think about it. And it begs the question: What keeps all those bacteria from decomposing you alive?
That’s silly, you say. I’m alive. Only dead things decompose.
Yes, but why?
What keeps all those bacteria from decomposing you alive?
As the new study points out, two of our most crucial defenses against being decomposed are toppled as soon as we die. Our immune system shuts down, and our bodies cool off. Bacteria like this; they don’t have an easy time growing in a hot body. (Think about it: When we have an infection our bodies develop a fever to ward it off.)Basically, a big part of life involves your cells waging a battle to the death with bacterial cells. As long as you’re alive and healthy, your cells are winning. Decomposition is when your cells lose.
One of the clearest descriptions I’ve read comes from Moheb Costandi’s “This is what happens after you die“:
Most internal organs are devoid of microbes when we are alive. Soon after death, however, the immune system stops working, leaving them to spread throughout the body freely. This usually begins in the gut, at the junction between the small and large intestines. Left unchecked, our gut bacteria begin to digest the intestines—and then the surrounding tissues—from the inside out, using the chemical cocktail that leaks out of damaged cells as a food source. Then they invade the capillaries of the digestive system and lymph nodes, spreading first to the liver and spleen, then into the heart and brain.
As soon as you die, your body essentially gets its first break from a war that it has been fighting every moment of your life.
When the bacteria start to win that war in a living person, we call it an infection, and we try to flush the invaders out of a wound. Or we go in with antibiotics to poison them.
Let’s pause for just a moment to appreciate those antibiotics. We thought we had outwitted bacteria. But now we’ve overused and misused antibiotics, giving the bacteria a chance to figure out our defenses. They’re adapting, becoming resistant to our weapons, and we’re already seeing the failure of some of our last lines of defense, leading to more infections, illness, and death.
Ultimately, we lose our battle with bacteria when we die. But until then, it’s pretty amazing to think of the fine line between life and becoming bacteria food. Imagine the evolutionary arms race that has led to an immune system so vigilant that it can fend off constant attack for decades.
I’m just grateful not to be decomposing right now.