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  • The most dangerous animal on Earth isn’t the shark, or the lion, or even the hippopotamus.

  • It’s so small, in fact, it could sit on the tip of this pencil. Biologists estimate

  • that they have killed nearly half of all humans ever born, and today accounts for more than

  • 45 million years of lost human life every year.

  • [SLAP]

  • BLEEP mosquitoes.

  • [MUSIC]

  • A mosquito is any of more than 3,000 species of tiny annoying flies in the family Culicidae.

  • Among those species that feed on blood, the vampire action is carried out solely by the

  • females, who require the proteins and nutrients in animal blood in order to lay their eggs.

  • Blood-sucking mosquito species have very discerning palates when it comes to which species they

  • feed on. Mosquitoes that prefer birds, for instance, may not suck our blood. Only a few

  • hundred species are actually known to poke tiny holes in humans.

  • Among humans, mosquitoes are known to be more attracted to some of us than others. I recommend

  • making friends with one of these people, and invite them to your next BBQ as a natural

  • bug decoy! And if you already get invited to a lot of BBQs, it’s probably you.

  • Mosquitoes can detect exhaled CO2 from over 100 feet away, so heavy breathers watch out.

  • They also show preferences for certain blood types, pregnant women, and particular populations

  • of skin bacteria. Body odor chemicals like octenol, lactic acidand this one, don’t

  • you laugh!… are skeeter magnets, as well as ethanol secreted through the skin after

  • weve been drinking. While we used to think insect repellents like DEET worked by blocking

  • a mosquito’s smell receptors, new research suggests that the bugs just really, really

  • hate the smell.

  • Although we call them bites, mosquitoes actuallypoke”. Evolution has molded the mouthparts

  • of theseectoparasitesinto highly-specialized face daggers, enclosed within a sheath called

  • the labium. As they enter the skin, they are unsheathed and the flexible mandible seeks

  • out a blood vesselOH MY GOD what is it doing?! MAKE IT STOP.

  • When the mosquito finally taps into sanguine sustenance it uses its tongue-like labrum

  • to slurp up a belly full of blood. Our immune system reacts to the foreign proteins in their

  • saliva, resulting in red bumps on our skin. So you really only have yourself to blame

  • for the itching.

  • But mosquitoes didn’t become the largest killer of humans thanks to us scratching ourselves

  • to death. In fact, it’s not really mosquitoes that do all that killing. The actual culprits

  • are even smaller.

  • Meet Plasmodium falciparum, the most common cause of deadly malaria. This microscopic

  • protozoan parasite swims its way into our bloodstream via the mosquito’s salivary

  • glands, where it infects liver and red blood cells, often resulting in a deadly fever.

  • When another mosquito feeds on malaria-infected human blood, the parasite can sexually reproduce,

  • mutate, and spread.

  • Today, malaria kills about a million people per year, and sickens half a billion. So what

  • can we do about it?

  • We do see signs of an ongoing evolutionary arms race against malaria inside our own genomes.

  • People who carry one copy of the sickle cell gene mutation, a trait common in tropical

  • regions like sub-Saharan Africa, show resistance to the disease, likely by disrupting the parasite’s

  • blood cell life cycle.

  • Yet malaria persists. Insecticides and other chemicals are effective, but often harm the

  • environment or wipe out beneficial insects along with the bad.

  • Anti-malaria drugs like artemisinin, while cheap and effective, carry a risk of resistance,

  • and theyre completely ineffective against viral mosquito-borne illnesses like Dengue

  • fever.

  • So, why don’t we just get rid of mosquitoes?

  • Is such a thing even possible? Yes it is. Maybe.

  • Oxford University biologists have created genetically engineered male mosquitoes with

  • a mutation that kills 100% of their offspring. When these males are released into the wild,

  • they mate with females, and all the eggs are duds. And in those places, and mind you this

  • has ACTUALLY been done, Dengue-carrying swarms have plummeted. This works.

  • Well, it works for US at least.

  • In some ecosystems, mosquitoes are important pollinators, or food sources for other organisms.

  • Eliminating mosquitoes, even just specific disease-carrying species, MIGHT lead to other

  • negative effects that we can’t predict. But does human health outweigh those environmental

  • concerns? Is expensive genetic engineering better than, say, a net over a bed? And could

  • it be, like science writer David Quammen says, that mosquitoes are in some ways defending

  • the world’s wilderness from even wider human invasion?

  • With their tiny swords, and their diseases :) Guarding the jungle.

  • These are difficult questions. They force us to put the health of our own species at

  • odds with another’s, and the answers aren’t simple. I wanna know what you think, I put

  • some links in the description to check out, so talk about it in the comments. What should

  • we do about mosquitoes?

  • Whatever the answer, weve got science on our side. And I THINK that’s a good thing.

  • Stay curious.

The most dangerous animal on Earth isn’t the shark, or the lion, or even the hippopotamus.

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B2 中高級 美國腔

世界上最致命的動物是什麼? (What's The Deadliest Animal In The World?)

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    Eating 發佈於 2021 年 01 月 14 日
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