Humans have allways lived in within reach of nature and forests, some more than others depending on where you live in the world. But how can we still not be immune to something like pollen by now? Something that we have been affected by every summer ever? Why doesnt our immunesystem adapt to it? Can animals have pollenallergy to?
In: Biology
So, just to expand a little on it. Traits that are REALLY bad get taken by selective pressures. Allergy to pollen isn’t particularly bad, I mean, it is annoying. But it does not prevent anyone from either surviving, or mating. So, it is out of selection. Also, humans did not evolve around this pollen environment, we are more of a savannah/dry environment. A few thousands of years mean nothing when compared to the millions of years it took for us to be…well what we are now.
I don’t have allergies so I guess technically I am someone who is immune to pollen. If I understand it correctly, allergies are an over response by your immune system not a deficient one. So your ancestors probably evolved in an area with low pollen and now when you experience large amounts, your immune system is like, whoa I am not used to that better get it out of here with lots and lots of mucus.
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As others have said, allergies are the immune system overreacting to harmless substances. It’s not really an issue of being “immune” or not. Plenty of people don’t have allergies or don’t have allergies stemming from pollen. I personally have a ragweed allergy, so I’m fine when flowers and trees are releasing pollen.
But to answer the question about why it hasn’t evolved away, it’s a mix of what other people have said about allergies not necessarily preventing people who have them from reproducing and the fact that overreacting is more advantageous than underreacting. Your immune system is capable of doing many things to get rid of pathogens. Inflammation and fever are a type of response that makes conditions harder on bacteria and viruses. If the body couldn’t do this, there would be a lot of diseases we couldn’t effectively fight off, but for some infections, the increase in temperature isn’t as necessary. And in the case of physical injury, the body can sometimes overinflame the area because inflammation helps to prevent infection and start repairing damage. But there’s a point at which those responses stop being helpful. A pollen allergy is one of those issues.
There’s also the fact that fear of allergies caused people to prevent their infants from being exposed to allergens because the scientific consensus was that it was safer that way, but we recently found out that early exposure to potential allergens while the immune system is still developing helps the body recognize that they’re harmless before the immune system is able to overreact when making threat assessments.
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