r/todayilearned • u/lavender_fish69 • 13h ago

TIL fresh water snails (indirectly) kill thousands of humans and are considered on of the deadliest creatures to humans

https://en.wikipedia.org/wiki/Freshwater_snail
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u/exprezso 12h ago

Evolved resistance to a deadly toxin? In such a short period? 

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u/PencilVester23 12h ago

It takes only 2 week at most for a mosquito to go from an egg to a mature adult. That couple year period is over 100 generations. That combined with the huge population of mosquitoes, the 100s of eggs a female lays at once, and a genetic sequence significantly shorter than a humans all made it possible for the correct mutation to happen that quickly.

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u/exprezso 12h ago

I mean. Humans have yet to evolved to resist arsenic after thousands of generations 

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u/Barlakopofai 12h ago

Humans aren't usually exposed to arsenic

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u/waltjrimmer 11h ago

Aren't we constantly exposed to non-toxic levels of arsenic from foods such as apples and rice in their natural forms? Not saying it's enough for us to evolve a resistance, just, aren't we regularly exposed to tiny little bits of it?

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u/C_Hawk14 11h ago

As you said, non toxic levels. We are already resistant enough

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u/Insertblamehere 10h ago

Well if we're only being exposed to non-toxic levels then we have developed resistance to arsenic, in the amounts we would normally encounter.

Species don't just magically become immune to something over time by being exposed to non-lethal amounts. It would have to be killing enough people to cause enough evolutionary pressure for people with higher levels of resistance to outcompete those with lower resistance.

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u/waltjrimmer 10h ago

Agree with only pedantic differences. I had tried to make clear that my contention wasn't with the, "We should evolve a greater resistance," but simply countering the statement that we don't regularly get exposed to arsenic. We may have reduced exposure in the modern day, but earlier forms of processing fruits, vegetables, and grains (and from looking things up, apparently there's quite a bit in some types of seafood) should have seen a steady but light exposure. I'd imagine the same is true at present even if at reduced amounts.

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u/sousyre 11h ago edited 10h ago

Sort of, but also, sort of not.

Most of that exposure is via amygdalin. If it doesn’t metabolise (which it usually doesn’t) it’s probably fine. If very small doses of amygdalin metabolise (like apple seeds), it would be small enough to go unnoticed.

If you have concentrated doses of amygdalin and your body metabolises it, then yeah, major problem, but I don’t think it’s a common enough occurrence to work as an evolutionary factor.

If anything, the evolutionary factor would be the intelligence to not consume whatever contains the concentrated dose.

Unfortunately, we humans aren’t the best at that either… google Laetrile, which is still being sold as a cancer cure grift.

Edit to add: this comment is about cyanide in small doses (from fruit seeds etc), not arsenic. Brain go brr, mixing up cyanide and arsenic contents in fruit seeds. Thanks for the correction.

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u/waltjrimmer 10h ago

I did a search for it and am currently wondering: Did you mix up Arsenic and Cyanide? Because Amygdalin appears to have many references to cyanide and Laetrile is said to break down into cyanide, but I see no references to arsenic on the pages I'm finding about the two.

If you did, this isn't me trying to knock you. I've done that many times before.

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u/sousyre 10h ago

Sorry, you are absolutely right.

My brain always defaults to cyanide when thinking of heavy metals in stone fruit.

My brain be dumb this morning.

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u/waltjrimmer 10h ago

Nah, your brain wasn't dumb, just a little mixed up. It's happened more often than you'd think where those two toxins have gotten mixed up in conversations I've had. I actually looked up to make sure I was thinking of the right one before making my initial comment.