Regenerative ability caused by radiation

Question

I know it looks like a lot of topics but hear me out here. I am not talking about some nonsense explanation for this ability but more of an evolutionary process.

Imagine that for numerous generations some humans survived in radioactive areas, over the years (I mean a looooooot of years) their capacity for regeneration evolved to counter cellular degradation.

Also, but I am venturing on a path I know less, could it be they have some way of never losing fragments of DNA (meaning nothing or very little is lost with each new cell created)?

So basically they would look like any human when they are in this environment, because their healing ability would be used to counter the radiation damage. But now imagine we take a member of this population and place him in an environment where there is close to 0 radiation, then could his regenerative body heal faster than one of a "normal" human?

QUESTION

Could it be possible for a human to develop healing ability through evolution in a radioactive environment? If yes, would it help him in a non-radioactive environment?

Post-script:

For each of your answers could you explain why it would be plausible or why it is nonsense, thank you! Oh and sorry if there are any mistakes, English is not my native language :)

Answer 1

Here is a mechanism for what you want:

1: In real life, each cell division is an opportunity for that cell to turn into cancer. That is why cancers usually happen in epithelial cells like gut lining, gland linings, skin: epithelial cells divide a lot. Epithelial cells also have a limited life expectancy; one rationale is that within a certain time frame they are more likely to have developed DNA damage and so they might as well be recycled. Very much like the replicants in Blade Runner - recycle them before they develop changes which make them dangerous.

2: In a very radioactive environment, the time frame during which a cell will likely acquire DNA damage is shorter. So these cells divide faster, to do their life's work in the shorter functional life span they have. Cells in such an organism have a faster growth rate.

3: Radiation can cause cancer in nonepithelial cells also - osteosarcoma being an example which one commonly sees arising in places where people have had radiation for a prior cancer. Bone cells do not have the same lifespan safeguards that epithelial cells have, but they could. If bone cells posed the same regular risk of cancer that epithelial cells pose, an organism with bone cells (and muscle cells, and glial cells etc) that lived fast and died young would be protected from cancer risk.

4: Your radiation adapted organism is full of cells that reproduce themselves, grow, then commit apoptosis suicide at breakneck speed - they have to do their work before they turn cancer. This would come at a high energy cost for the organism but so be it. These things would resist cancer because the cells would be born and die so quickly. That fast cellular growth rate also means they heal damage very quickly, radiation notwithstanding.

Answer 2

No.

radiation damage is actually only a little direct damage to the cell: it is mostly the cell recognizing some minor damage and then killing itself in a process called apoptosis

This is done far, far sooner than the damage usually has any impact because of the danger that damaged DNA poses: cancer.

Cells will happily kill themselves if they can save their host from cancer.

So any resistance to radiation will mostly involve reduncancies and processes that make sure that a cell can take more damage before it terminates, not direct radiation hardening. An improved resistance to cancer is a positive side effect.

If your organism evolved in a environment where actual, physical, radiation hardening is needed they wouldn't evolve at all because that place would be sterile.

see for example Deinococcus radiodurans, the most radiation resistant organism on earth. That tough cookie just has tightly coiled and multi-copied DNA, nothing that involves unusual repair to the cell structure.

Answer 3

All multi-cellular life regenerates, healing wounds, and this is fueled by eating. The mechanism to repair damaged DNA is caused by telomerase, but it's an energetically expensive molecule for the body to create, so it usually doesn't create enough to counter cancer long term, but common expsoure to radiation would likely give a reason for evolution to select for more intensive DNA repair, especially if they had an abundant energy source (say, for example, the radiation.)

So the question is, "Could humans adapt to feed off of radiation?"

To look at this answer, the first question would be can -any- creature that can survive intense radiation.

And yes, there's already one species that has adapted to it. And not only to survive in it, but it feeds off the radiation. This is a black fungus that lives in the core of Chernobyl reactor. This is a place that melts robots that go in, and this fungus is thriving there.

So the next question is, "What dark secrets of evolution has this fungus unlocked that allows it to survive there? To feed there? Is such an evolution so far off track of humans that we could never hope to..."

It's melanin. The same stuff that gives Northern European freckles and makes African's skin dark, and makes other people tan. It's how we naturally produce Vitamin D in sunlight. We're already naturally feeding off of radiation, albeit in much smaller doses. Enough generations in steadily higher radiation environments, and we'd quickly (evolutionarily speaking), as a species, be able to chillax in the Chernobyl reactor along with the fungus there, assuming our sweat could keep pace with the heat increase. Further, melanin not only absorbs the radiation, but also blocks it from getting deeper into the body, cutting out a lot of radiation to inner cells.

Your idea is spot-on doable without anything weird needed. That said, any human so evolved would look at the typical deep African and call them white. Melanin is a darkening pigment, and the black fungus in the reactor is called that for a reason. These people would be printer-ink black or darker.

Answer 4

could it be they have some way of never losing fragment of DNA

With radiation damage DNA is not lost in the sense that it is gone, but just made unusable. Imagine like a scratch on the surface of a CD.

Same when DNA is damaged by radiation: some atom or bond is damaged and the functionality is gone.

Since we live already in a radioactive environment (background radiation is non zero, and we are also exposed to UV radiation from the Sun), our body has already some repair mechanism, which can cope with small damages. The yield of this mechanism is however not 100%, but rather 99.99x%. This means that sooner or later some damage won't be repaired.

Increasing the background radioactivity level may lead, over generation, to the selection of a more efficient repair mechanism, let's say, for the sake of this answer, that it goes from 99.999% (1 error in 100k repair) to 99.99999% (1 error in 10 million repairs).

The mechanism would only work for damages to the DNA, so for damages induced by radiation. If your subject would get a wound by cutting his finger while chopping an onion, that would not affect its DNA, so there would be no accelerated healing.

It would however give improved resistance to cancer, as long as cancer is the consequence of damage at DNA level, interfering with the normal behavior of the cell.