Or so I heard Michael from Vsauce say. Checking around it seems to be true:
“Studies at the Oak Ridge Atomic Research Center have revealed that about 98 percent of all the atoms in a human body are replaced every year. You get a new suit of skin every month and a new liver every six weeks. The lining of your stomach lasts only five days before it’s replaced. Even your bones are not the solid, stable, concrete-like things you might have thought them to be: They are undergoing constant change. The bones you have today are different from the bones you had a year ago. Experts in this area of research have concluded that there is a complete, 100 percent turnover of atoms in the body at least every five years. In other words, not one single atom present in your body today was there five years ago.”
I have two questions;
Then why do we get diseases like cancer - from long term smoking or long years of exposure to the sun. If the lung atoms are being replaced it seems that should re-set the abrasion?
If the atoms that make up brain cells get replaced, how does our memory remain?
Sorry if these are stupid questions, but on some level this doesn’t make sense.
Cancer is a property of the DNA in your cells getting messed up and replicating endlessly. It’s a problem with the structures formed out of atoms - the DNA. If you were to replace those atoms in place, you’d still have the same results.
Same with memories. They are a property of the structures formed by your neurons, not a property of the atoms themselves.
Well first of all, it is not strictly true, on a very nitpicky way. As there are more molecules of water in your body than litres of water in the world, you have a couple of molecules of water that were drunk (or sweated or pissed) by any historical person you wish to think about, provided they lived long ago and the water has had the time to mix well “enough” with the rest of the water in the world. So a couple of molecules of water and calcium atoms in your bones will still be there, only in a different place. There was a thread about that.
Then the memory and the cancer due to smoking: it is a variant of the Ship of Thesseus paradox: The atoms may not be the same, but the damage done to the structure of the cell and it’s DNA and RNA by cancerigenous substances remains when you swap the atoms one by one in the same location, and the memory is due to things like synapses, their number and strength, action potentials, and much more (it is really complicated, I don’t think experts understand it completely), but those things remain invariant swapping single atoms one at a time, one after the other. And sometimes you forget things, and some smokers do not develop cancer (yet).
Saying that every atom is “replaced” is a bit misleading. It doesn’t mean that individual atoms are replaced within persistent molecular/cellular structures (except in rare cases), nor that anyhing is “reset” to an original state.
The hypothesis, if correct, surely just means that entire cells are dying and being replaced by new cells of the same type. The new cells will contain many “new” (to your body) atoms derived from food. Cells of the same type will be somewhat different from the old cells. In particular, making new cells involves DNA replication, so the new cells will contain mutations.
The way that Times article is worded actually makes it sound like Oak Ridge is the city Dr. Paul C. Aebersold is from, not a national lab that he works at.
FWIW Paul Harvey brings back found memories of the radio on in the car with my dad …
Clearly the factoid is not exactly based on hard up to date evidence … but the point being made then is exactly the point discussed in answer to the op.