I chopped off around 3-4mm off the tip of my left index finger as a kid with a lawn trimmer. 20 years later, I punched a nice groove around 3mm deep into the tip of another finger tip while trying to get tea out of a tea tube [0] (don't buy these things).
It took weeks, but both times, the tips grew back perfectly round and smooth, even the fingerprints are back. The regrown tips felt a bit numb for 1-2 months, but then everything was back to normal. The second time I asked a friend, who is a medical doctor, how the body "knew" the form of the fingertip and the fingerprints. Where was this information stored? His answer was basically: we have no idea, just be grateful it works.
Regarding how the body "knows" how to form missing pieces, might be worth checking out Michael Levin's research regarding bio-electricity. Most interesting finding to me is that once modified, the animal bodies continue to produce different parts as if there is some electrical "memory" in the cells.
I caught my finges in the chain of a swing as a child and tore about half the pad of my pinkies away to a similar depth, one narrow strip was still attached so I held it on with bandaids after washing it. It grew back together but now there is an offset or fault line in my print.
Its not that sharp, its a tube of brushed aluminium around, around 2cm in diameter, the walls ca. 1 mm thick. It's tapered at the top (which can be seen in the image). I put tea in there and coudldn't get it out after it had swollen in the hot water. I opened the bottom, put the handle of a wooden cooking spoon in, hold the cooking spoon with both hands and pushed the tea tube against a wall. The tea suddenly gave loose, and the tea tube shot down the cooking spoon to where my hand was holding it. It only hurt after the shock of seeing a groove in my fingertip was over, and it seemed like and eternity until there was blood (but then lots of it).
Some time ago there was a post on HN about one scientist who made a simple organism to grow two heads by messing with the intercellular magnetic fields. No DNA changes, just magnetic fields.
There's a way to check this hypothesis without cutting fingers. Salamanders can regrow tails. So get a salamander, cut its tail, use some magnetic field generator to mess with the regrowth process and see what happens.
The scientist is Michael Levin and his work, while absolutely legit, is so far from current mainstream that I am a bit afraid it might not be adapted for medical use in our lifetimes. Or possibly only after a major upheaval, much like mRNA deployment was accelerated by Covid. (mRNA co-pioneer Dr. Katalin Karikó ran into similar problems - the concept of mRNA was too revolutionary to be fully grasped by the PennU administration.)
Pure wild speculation: I suspect that an awful log of our biological form is fractals formed from chemical gradients, with our DNA controlling the amounts of each chemical, both how fast they're produced and consumed. Included in this are some wild "Programs" were Chemical A causes Chemical B to be produced, Chemical B produces Chemical C and chemical C shuts off chemical A - In wild patterns that eventually form the beauty of our bodies. On a mass scale, with dozens of signaling chemicals and switches flipped - Organelle A produces chemical B and C and they osmose. B spreads far and wide, and an organ grows wherever B is concentrated. C doesn't spread, and eventually it grows concentrated enough to shut itself off. Thus, the physical limits of a body are formed.
Fingerprints would then be where this all happens on a micro scale - Running the game of life in 3d on the cells of your body, until they reach an "end state" of a stable limit of your skin.
Turing’s diffusion/reaction algorithm involved this. As you intuited, it is a good system for making fractal-like designs and patterns. Cheetah spots, zebra stripes, maybe even 3D structures like capillaries...
But, such a system can’t make discrete forms—like a nose.
There’s something else going on.
For instance... deer grow antlers every season (antlers are not horns; rather, they are complex structures with tissue, bone, skin, nerves, etc) Anyway, if a growing antler is nicked, scar tissue will form... no big deal, right? But, this is where it gets weird... When the antlers fall off and then grow the following year, the scar will be present on the new antlers. Let that sink in.
There are several parts embryo development that does operate on chemical gradients especially the initial stages. But like most of biology it gets really complex and isn’t limited to any one approach.
For example as you gain fat tissue you need to increase the number of capillaries feeding that tissue, which in tern needs to link up to arterioles and arteries on one side and veins on the other. https://www.ncbi.nlm.nih.gov/books/NBK53238/ This happens well into adulthood.
One of my finger nail was wrecked last year and it looked horrible. I thought it would never grow back. Now I can’t even tell which one had been wrecked.
My 3yo daughter got a blood clot in her thumb that caused the entire tip above the last knuckle to get purple, then black, then essentially die off due to lack of blood flow.
She was in the hospital for something different at the time so doctors were able to watch it closely. It looked really bad: blackish grey and stiff like she had gotten frostbite.
The hand specialists warned us that amputation might be necessary if it gets infected, but said ideally they just "wait and see."
Sure enough, three weeks later they were able to literally just pull off the dead part and find a new thumb growing underneath!
I worked med-surg for a number of years, and every so often we’d get older adults admitted to the floor for peripheral vascular disease. Same thing happens: toes get dusky, then necrotic. The treatment is painting the toes with Betadine and wrapping with gauze. I never considered that this might be part of regeneration that doesn’t come to completion because of chronically poor blood flow.
There is more than one tale of nurses going in to rearrange the bedding or taking the gauze off only to find the affected toe had fallen off, and the patient not noticing it.
That’s pretty remarkable and an amazing example. It’s not just the flesh, but also the nail that was regenerated. You’d expect that the death of the nail bed would mean no new nail, but there it is.
True statement. I lost a finger tip in a mandolin making potatoes lyonnaise. It mostly grew back. However, it has never felt the same. It's like the nerve endings in the finger tip throw unhandled exceptions. Some say properly cooked french food is worth it. i agree.
As an accident-prone home chef myself, I highly recommend a pair of kevlar "cut gloves" for anything involving a mandolin, peeler, or grater. They're just a few bucks and can save you a lot of tears.
Seconded. I also lost a fingertip to a mandoline when slicing potatoes. On Xmas eve, just as guests were arriving. And oh boy did it bleed!
My fingertip took over 3 years to regain full feeling, and it's still slightly flattened compared to the rest of my fingers. (I made the front page of reddit with an animation of the regrowth!)
Since then I bought cut gloves because I'm now semi-phobic about using the damn thing without them.
As somebody who has also lost a chunk of my finger to a mandolin (regrew including print) this thread has convinced me that mandolins are just not worth it.
I took the pad of a finger off while drying my mandolin blade after washing it the first time. These gloves are a must whenever the mandolin is out.
(For anyone keeping track in this thread: the sliced portion has feeling, but no finger print, it all looks like scar tissue. The urgent care doc used a gelatin sponge (gelfoam) to stop the bleeding. Dunno if that explains the outcome)
> I lost a finger tip in a mandolin making potatoes lyonnaise.
I had to look this up because I only knew of mandolin the instrument and not mandolin the cutting tool. It did give me a very interesting mental image, though.
How long is never? I have some cuts with nerve damage that slowly improved (or was it my brain gradually learned that the different feeling is not foreign?) over many many years, like more than 10. No serious ones on my finger tips though.
I had an all-the-way through my palm cut that also went the full length top-to-bottom. There were various "dead/numb", "tingly", etc, parts for 16 years, that all sort of went away in the last year of that 16 and felt normal from then on.
Interestingly, that’s quite similar to what developing a new sense of smell was like after nose surgery! I haven’t smelled burning rubber from a cup of tea in a few years so it’s nice that the brain/nerves finally wired themselves up properly.
I chopped off the tip of my index finger about 20 years ago and then got it sewn back on. Another dude I was working with did the same and didn’t get it sewn back on. Four years later, his was good as new, and mine was healed but I couldn’t press on it without a lot of pain. I had to give up playing the guitar, and still can’t press on the strings. Typing is a little bit weird because I can’t feel the keys, and I end up in slightly wrong positions because you’re supposed to be able to feel the little nubs on the home row.
I suppose... in theory you could chop it off again. (Presumably not worth it if it's only in pain under significant pressure though.) Probably not something you'd want to do yourself. I actually kind of wonder if you could find a surgeon willing to do it!
I’ve tried some funny shuffle like sanding it down and doing hundreds of punctures with a needle. It always seems to grow back as scar tissue. I think I might have to chop it deeper into the good part, and that might not work out as planned.
Bone fracture healing is also, exactly, regeneration. Regeneration of fingertips in small children is almost universal, provided you don't stitch it up.
George Becker's book "The Body Electric" is the most complete exploration of regeneration I have encountered to date. Becker's suspicion was that we gave up general regeneration in exchange for cancer resistance.
Came to mention this book - the author is Robert O. Becker and it was published in 1985. Mike Levin (mentioned elsewhere in this thread) was greatly influenced by this book.
The body never forgot how to regenerate, it just learned how to scar - to prevent infection - or at least that is what I heard a wake forest researcher say after helping grow back a finger with stem cells from the individual and powdered proteins from a decelled pig's bladder.
Similar to my own story, cut 3/4mm from the side of my thumb. Panicked and tried to reattach it, but later I read about the regeneration so, I removed the tip (ripped it) and just moved to wait and see. A few weeks passed and I saw how every layer of skin, grew back. Leaving a hole at the center first, and progressively all of it., was filled. I have pictures of it. You can’t tell know, pretty impressive I was 42 ATM
This is one of my favorite weird biological facts. It actually happened to a friend of mine. It shows that the programming for regeneration is in there, we just need to activate it.
Got infection under fingernail. Turned purple, swelled up like a grape. Got hard and calloused. Then one day it emitted vile stuff from under the fingernail, deflated. A couple days later, callous fell off. Fingertip underneath was half-width but complete. Over next year, the other half grew back - fingertip got a little wider over time until it's the right width.
Now I can't quite remember which one it was - they are all the same and unscarred.
> The signal made by the nail stem cells — called Wnt, for all you bio buffs — can orchestrate growth all over the body. It even coordinates the formation of limbs and some organs during fetal development.
I wonder what would happen to my right pinkie. When I was young I accidentally burned the fingerprint off on a curling iron. It's not a large section and there's no scar tissue, just a spot on my pinkie which looks more mosaic than swirly.
It's been that way most of my life as it happened when I was a single digit age.
If it would grow back, it should grow back with the original fingerprint.
Isn't the more fascinating element of this story the lack of medical understanding regarding what seems like a fairly well-understood body part (a fingertip)? How much knowledge could be gained simply be seeking seemingly minor examples beyond current understanding, even in the absence of financial incentive to explore?
Three more anecdotes here: my mother, uncle, and wife chopped off the tips of their fingers (him doing farm work, them chopping food) and had them grow back. The article talks about kids, but the former two were in their 40s and the latter in her 20s at the time.
Not exactly the tip, but I sliced a good 1/8" or so off my thumb print once with a table saw. I was very impressed that my thumbprint mostly grew back, except for some scar pattern in the middle.
I lost the upper phalanx of one of my thumbs when I was 6 years old in an accident. They could not attach it and never grew back. 10 years later I read about an American scientist that managed to grow back full body parts using some kind of pigs but extract... I wish that science was more advanced.
It took weeks, but both times, the tips grew back perfectly round and smooth, even the fingerprints are back. The regrown tips felt a bit numb for 1-2 months, but then everything was back to normal. The second time I asked a friend, who is a medical doctor, how the body "knew" the form of the fingertip and the fingerprints. Where was this information stored? His answer was basically: we have no idea, just be grateful it works.
[0] https://www.hochland-kaffee.de/media/catalog/product/cache/1...