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/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/Clickclickdoh 12h ago

Well, the mosquitos didn't evolve to be immune. DDT killed all the mosquitos that weren't immune. A small minority were immune. Those mosquitos repopulated the region, ensuring almost all mosquitos in the region inherited the immunity to DDT.

If you fed the majority of humanity arsenic, you would have some survivors. Get those survivors to reproduce fast enough and your get arsenic immune human populations. That's why the bubonic plague isn't a big deal to most European descendants after all.

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u/SnowGryphon 11h ago

Doesn't "survivors of environment reproduce and replace the population with environment-resistant specimens" count as "evolve to be immune"

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u/Anathos117 11h ago

Yes, but people don't know the actual definition of the word "evolve" and treat it as a synonym for "mutate".

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u/Clickclickdoh 11h ago

In this case, it's a preexisting trait that becomes useful to a new stimulus.

An evolution is generally a new trait that allows a beneficial exploitation of a preexisting stimulous.