1. Meteor
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    Meteor Active Member

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    Human adaptation and radiation resistance

    Discussion in 'Research' started by Meteor, Mar 29, 2015.

    Ok so I'm curious as to how Human adaptation might work here. In the little set up I have a nuclear holocaust takes place around 2155. In the story I have it set so that after numerous generations Human adaptation kicks in and around 2327 Humans who are resistant to radiation have emerged. I read about an experiment where a common bacteria was constantly exposed to radiation. New bacteria was grown from the remains and after about 20 attempts a new type emerged that could rapidly repair radiation damage. So I was wondering if Humans might adapt in a similar way over the course of numerous generations of forced/unaware exposure. Can anyone explain how this 'might' work or how long the adaptation process could take for something like this? Thank you in advance for taking the time to read this.

    The link to the article is here: http://io9.com/new-study-suggests-one-day-humans-could-be-radiation-re-1543961839 (its not to long)
     
  2. Chinspinner
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    I don't know the answer to the specific question, but a few facts I have gleaned over the years: -
    • Some well documented nuclear near-misses, such as Windscale or Three-Mile Island never actually exceeded the natural background radiation, despite mass hysteria.
    • The effects in the area surrounding Chernobyl are much more limited than anticipated. People still live in the exclusion zone without ill-effect.
    • Natural sources of radiation are very prevalent in the environment, and come from cosmic rays, food sources (bananas have a particular high source), radon gas, granite and other dense rocks, and others. The collective radiation background dose for natural sources in Europe is about 500,000 man Sieverts per year. The total dose from Chernobyl is estimated at 80,000 man sieverts, or roughly 1/6 as much.[1] However, some individuals, particular in areas adjacent the reactor, received significantly higher doses.
      http://en.wikipedia.org/wiki/Comparison_of_Chernobyl_and_other_radioactivity_releases
    • In 2009 the levels of radiation found in Chernobyl were significantly lower than those found on an airline flight, and generally lower (other than specific locations like reactor chambers) than natural background radiation.
    • Nagasaki and Hiroshima are other examples.
    So I am wondering why we would need to develop a resistance.
     
    Last edited: Mar 29, 2015
  3. Meteor
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    Wow, that's actually really interesting. I wasn't aware that we had that much exposure via background radiation and natural sources. I suppose that does pose the question as to why we'd need to develop immunity. So I would guess that the doses would have to be deathly high for our bodies to perceive the need to adapt an immunity then? I'll have to keep this in mind and keep digging I suppose. Thank you for the answer. :)
     
  4. Jack Asher
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    Jack Asher Wildly experimental Contributor

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    This will probably help a lot.
    [​IMG]
     
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  5. GingerCoffee
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    There may some things you aren't considering here.

    First, what do you mean by "Nagasaki and Hiroshima are other examples"? Examples of what? Cities that recovered? Could you expect the same if the nuclear holocaust was on a much larger scale?
    Long-term Radiation-Related Health Effects in a Unique Human Population: Lessons Learned from the Atomic Bomb Survivors of Hiroshima and Nagasaki

    Then re: the radiation levels at Chernobyl, isn't the Chernobyl number in addition to background radiation? And is that annually? Radiation damage is cumulative no matter the time between doses.

    So one needs to know what was the scale of the disaster, and how long does the radiation contamination continue?

    But I agree with you, a lot of the scenarios in fiction are probably inaccurate.
     
  6. GingerCoffee
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    Re adaptation and resistance, human evolution is very slow. To adapt genetically, it would take thousands of years. Humans use technology to adapt to hazards in the short run. For example, black skin took thousands of years to evolve offering protection from UV radiation. When a light skinned person moves to the tropics, they need hats and long sleeves.
     
  7. Chinspinner
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    Yeah, I was just getting across the idea that the common conception of a nuclear winter that kills off all life on earth (bar one flower amidst the rubble) is mistaken.
     
  8. GingerCoffee
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    Unless thousand of nukes are used.
     
  9. Meteor
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    Okie d0kie so in reference to the scale. Inaccurate or not I'm going with the "Overkill is the best kind of kill." saying with this one. That's what I often heard in my time as a Soldier in the Army. Imagine if you will, all of the nuclear arsenal of China, Russia, the US and various unmentioned countries retaliating against one another. Oh and on that note a new power source has been utilized by said nations. In Europe and the North America they use a process called gamma voltation. Yes, I know voltation isn't word before we go there.(at least I don't think it is)You convert radiation directly into electricity. The US and Europe have close to a dozen plants along with various other allied states. They include S. Korea, Japan, Australia, Kenya and a few others.

    China and her allies managed to develop effective methods of using nuclear fusion. So they're using a little more than a dozen of those plants. I figured that by this time at the least we'd weaponize space like maniacs. Ion cannons, rail guns and that sort of thing. All of which are powered by fusion and gamma sources. Some of those orbital structures crashed and were shot down, others survived. I assumed that nuclear contamination would last decades if not centuries on such a scale.

    Oh and thank you for the chart. I'll be using that pretty often I'm sure.
     
  10. GingerCoffee
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    Adapt with technology. It fits with your theme/genre and it's realistic.

    Adapting genetically, umm, you might get away with it if the genetic adaptations were GMOs. It would take 40-50 thousand years for a species that reproduces as slowly as humans to evolve and the humans would have to survive to reproduce for that to happen.

    It would require a lot of research in genetic science to get it right. I know a lot about genetics and I'd have to do a ton of research to know which adaptations would be needed and they'd be incredibly complicated, more than the reader would be able to follow.
     
  11. Meteor
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    Alright, got it, genetic modifications or technology. I had thought about following through with the idea of humanity utilizing nano-tech by this time in our history. Billions of little machines running around in the body fixing the broken parts as they broke. I do know that that level of technology is PRETTY out there so I dropped the idea. I came to the conclusion that we might not have such technology by the next century. Primarily due to how we as humans operate. Corrupt politicians, misusing funds and people crying wolf over anything they don't like or approve of these days.
     
  12. GingerCoffee
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    If you wanted to go medical, if the radiation levels were low enough people could walk on the surface without getting a lethal dose, there might be cures for a lot of cancers and birth defects might be manageable with various interventions from genetic testing and abortion to gene insertion.

    But if radiation levels were high enough, no one could be exposed to that without serious illness and death. Your gut lining and skin sloughs off and your hair falls out. You can't survive much of that. I think you also get cataracts but I'm not positive about that without checking.
     
  13. Chinspinner
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    Yeah, but not long enough for some evolutionary process to occur in humans.

    Then again, if the radiation killed off those most susceptible to the conditions it causes there could be a leap...
     
    Last edited: Mar 30, 2015
  14. Meteor
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    I did some reading and yes cataracts are one of the things that can happen. I think its interesting how something you can't see can destroy the body so easily and quickly. What I was hoping was to find a way to prevent such lethal side effects genetically. I wasn't aiming for total immunity exactly but, enough resistance that severe side effects wouldn't appear after just hours but, rather a few days.
     
  15. Chinspinner
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    You can't just use a vague anti-rad medication as a plot device?
     
  16. Meteor
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    I had considered this too but, I don't like being entirely vague. I guess I'd have to be vague regardless of the approach I take though. This is complex stuff, lots of thinking here. At any rate I think I'll settle on something with all the information I've been given here. I'm out for the night at least. Thanks a bunch for the help guys. :)
     
  17. GingerCoffee
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    You would get some resistance, but it would take a whole lot more genetic changes to have enough resistance. More than likely anyone surviving would have done so because they were less exposed.

    We have inbuilt variation in the human genome, but not that much. We have enough that a single deadly disease might leave resistant humans behind to reproduce. A good example was the introduction of Myxomatosis into Australia in a failed attempt to get rid of the rabbits that had been introduced with European immigrants. It killed about 95% of the rabbits and the remaining 5% repopulated the country with resistant rabbits.

    The reason that works is there is a good likelihood of an existing variant gene already in the population that provides resistant to the one or few means the microorganism has to invade a cell.

    But when you have something like radiation that has an affect on multiple cells in multiple ways, there is no single mutation that provides resistance to such an assault.

    Genetic science is fascinating. It's within my field of practice in infectious disease. There are many interesting aspects to survival and reproduction. A microorganism has to have a route of entry that usually involves a particular cell membrane protein.

    Radiation, on the other hand, causes massive damage to every rapidly dividing cell in your body. Take a look at bone marrow transplants where we purposefully give the patient a near lethal dose of radiation. The bone marrow is destroyed on purpose then replaced with a marrow transplant. Without the transplant, no one survives.

    One of the workers at Chernobyl was given a transplant that saved him. Trouble was finding matches quickly enough for the rest.

    The other problem we have with bone marrow transplants is you have to support the entire GI system while you are waiting for the patient to recover from the radiation damage. That means you must feed them with something called total parenteral nutrition. You also have to make a massive effort to protect them from infection until the marrow transplant is functioning again.

    It's not practical you would have survivors because of existing genetic variation. With smaller doses of radiation, sure. But not with planet killing doses.
     
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  18. ChickenFreak
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    Remember that genes don't form in response to hostile circumstances. The gene is (or genes are) there anyway; it's the hostile circumstances that make the gene valuable.

    If the radiation kills everyone who doesn't have the radiation-resistant gene, then pretty shortly everyone still alive will have the gene, by definition. Children who don't have the gene will promptly die. Children who do have the gene will live. So you'll be pretty much pure-breeding for the gene within a generation.

    If the radiation doesn't kill everyone, you'll have to decide what it does, and what the gene does, before you can answer your question.
     
  19. GingerCoffee
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    I'm sure you know this is only true for slowly reproducing species. Natural selection favors variation in the genome as a survival means. But I wanted to comment on it.

    Rapidly reproducing organisms, on the other hand, can rely on mutations to create a resistant strain. In some microorganisms, the mechanism of genetic repair gets switched off when the organism is exposed to a toxic environment thus speeding up the rate of mutation.

    They also borrow genes from the environment but that's another story.
     
  20. Steerpike
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    Humans already have enzymes that correct for errors in DNA. If you're thinking of a way that humans might adapt one answer might be that error-correcting enzymes evolve to have a higher rate of detecting and repairing errors in DNA. Mutation from radiation works in others ways, as well, though, so the overall issue is more complex.

    As for mutations not responding to hostile circumstances, that's been a subject of a lot of debate. There have been studies in bacteria showing that in response to certain environments (like a specific food source the bacteria can't normally use) the bacteria evolve at a faster rate than one would see as a result of random mutation. One of the first such studies, published in Nature is here:

    There have been a number of subsequent studies, but it seems like the question is somewhat unsettled. The part that is unsettled may just be arguing over the mechanism. Another paper from 2006 found adaptive mutation, and supports the idea that they don't occur at the expected rates for random mutation: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1899370/
     
  21. Steerpike
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    Steerpike Felis amatus Supporter Contributor

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    Hmm. I didn't know the site was going to embed the Scribd link :eek:
     
  22. GingerCoffee
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    Again, that's if the initial exposure to radiation was not lethal. But DNA repair is a viable mechanism for a novel.
     
  23. ChickenFreak
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    That's interesting. I could believe, in theory, in an idea that in harsh circumstances there's a higher incidence of spontaneous mutations. I would have a lot of trouble believing in "intelligent" mutations. But a higher incidence of mutations could give you an "infinite monkeys on infinite typewriters will eventually produce Shakespeare" effect--if there are a larger number of mutations, the odds of some of them being beneficial are higher.

    I say all that before reading the article. I'm bookmarking it to read.
     
  24. Steerpike
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    Steerpike Felis amatus Supporter Contributor

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    Yeah, it's pretty cool. I don't think it is "intelligent" per ser, but tells me there are probably mechanisms at work that we still don't understand. I remember reading that paper in college (my undergrad degree is in Microbiology), and it looks like scientists still aren't entirely sure what is going on in that sort of situation. I haven't seen any studies looking for similar phenomena in higher animals, though maybe there are some out there.
     
  25. GingerCoffee
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    It wouldn't be adaptive for a slowly reproducing species.

    As for not knowing the mechanism, I'm not sure that isn't about not knowing all the mechanisms. I'll try to find the paper on the disabling of the repair mechanism resulting in an increased mutation rate. These things are not intelligent in any sense. They are the result of natural selection pressures.

    Edited to add: I see the problem, that Nature article is from 1988. Science is moving very quickly in the genetic field, but all science has moved a long way in 27 years.:p
     
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