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Comment by netwanderer3 | Hacker News Reader

According to the evolution theory, eventually our DNA will evolve to adapt to its external environment so does this mean given enough daily exposure over many generations, at some time in a distant future our immune system will no longer consider those particles as foreign and thus will not fight to eliminate it? There would be no dementia by then if it was indeed caused by inflammation triggered by the immune system. I know this sounds pretty stupid but human bodies are weird machines still not fully understood by today science. If some people within the same race could be allergic to certain types of food that are completely safe to others without any proper explanations (eggs, peanuts, etc...) then anything is possible. I'm sure there are people out there who live to 90 without getting dementia even in heaviest polluted cities.

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Yes and no. Evolution theory would require those who get dementia to go extinct. Usually by the time you develop dementia, you already reproduced, so even if some people become "immune" to pollution, the others won't get removed from the gene pool.

This is an interesting angle. Next generation will pretty much be exposed to pollution by the moment they're born. Technically their kids will inherit a slightly mutated version already even though it might not yet be enough. Does our gene "remember" how much exposure it had accumulated from the previous generation? We often hear from the news how they found some individuals who were immune to certain diseases due to a specific genetic mutation. Your kids don't carry the exact DNA as yours since it's a combination between a father and a mother so it will always be a new mutation.

Does our gene "remember" how much exposure it had accumulated from the previous generation?

Not as DNA. The main thing that controls evolution is failure to reproduce. Life experiences have only a very short term effect on how DNA is packaged.

it will always be a new mutation

A "mutation" is not the same thing as a "permutation". The combination of DNA from two parents is not itself mutation.

Transgenerational inheritance is what this is technically called, and is a contentious topic about whether or not it exists in humans and to what degree. There's been studies from people who's grandparents have gone through famine and those grandchildren tend to be shorter or leaner than those who haven't, but AFAIK these are just associations and nothing causal has been found in humans to suggest what happens to you might affect your grandchildren. That being said, being exposed to pollution is not going to be great for your sperm or eggs.

And I know you are worried about what the next generation breathes, but consider that what you were exposed to was much worse, and what your parents were exposed to was worse still, and if your grandparents lived in cities they experienced awful pollution, second only to perhaps what your great grandparents may have been exposed to during the industrial revolution. Air quality has gotten better than it was in 1980 and much better than 1880, but there is still a long way to go to reset the damage of rampant consumer culture on our environment and health.

Also to your point on how mutation happens: its random and rarely beneficial. If you go out in the sun without sunscreen, that UV light penetrates your skin and encourages your skin cells to produce more melanin, but it could also damage your DNA, break a tumor suppressing gene, and give you skin cancer.

Your bodies DNA replication machinery also has an error rate which can be worked out, and you can extrapolate that to get a rate of mutation. Knowing this rate can give you an estimate of how long ago two species diverged based on the number of different bases when you line up their DNA sequences against eachother, for example.

As far as I understand it, evolution only really happens if the survival of the fittest principle also applies. Modern science does good job keeping people who would otherwise could not survive alive. I think that the answer to get rid of allergies will come from science rather than the natural process. (If ever)

Not just that, evolution is more about reproduction of the fittest, than survival of the fittest. Any health effects that don't manifest until 40 or later aren't likely to have much influence on evolution.

A slight hair splitting here with your phrasing.

You've got it backwards. DNA doesn't "evolve to addapt". Variations get copied and passed down except for those within individuals that didn't reproduce. Sometimes an entire lineage doesn't reproduce, that's extinction. So, there's no "eventually".

Our bodies may not be "fully" understood. But there's no points for an argument from ignorance.

Still there may be people that live to 90 without getting dementia in heavily polluted cities. However, that's down to natural variation.

That only presupposes that these adaptations are evolutionary beneficial to us - if we live long enough to breed and see our offspring breed, it doesn't actually matter if we develop those adaptations. Selection via ability to breed is how evolution works, and we've largely circumvented that.

Should I move near Chernobyl ?

It depends how near. I've read that living in the outer parts of the exclusion zone is likely to reduce your lifespan by a week or two. Depending on the city, that actually might be an improvement.

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