Cruel Intentions

This Australian spider evolved to kill us — here’s why

This will seriously freak you out.

Fear of spiders is so common it consistently ranks in lists of the most common human phobias.

A study published in October in the journal Proceedings of the National Academy of Sciences gives us yet another reason to be terrified of spiders — or at least, one deadly Sydney funnel-web spider. It seems this particular Australian funnel-web spider has evolved a deadly defense system to target vertebrates.

Specifically: humans.

The Sydney funnel-web spider's venom fascinates us just as much as it kills us. The venom's neurotoxins can cause death within 15 minutes after the spider's fangs pierce human flesh.

The spider kills using toxic chemicals known as Delta-hexatoxins, which attack the nervous system. Symptoms include muscle spasms, vomiting, profuse sweating, and, of course, death.

A May 2015 photo of a funnel web spider clinging to the bark of a gum tree in the Palmer river district of Cape York, Queensland, Australia. One needs to be aware when strolling through this remote bush, it would not be nice to be bitten by one of these scary spiders.Photography by Mangiwau

While the funnel-web isn't the only spider to inject humans with poisonous venom, the evolutionary adaptation to target humans specifically is quite distinct.

The spiders originally deployed this lethal defense mechanism against other insect predators, but funnel-web spiders — male funnel-web spiders, in particular — have seemingly evolved to kill humans with their venom, too, the researchers found.

INVERSE IS COUNTING DOWN THE 20 STORIES THAT MADE US SAY 'WTF' IN 2020. THIS IS NUMBER 16. SEE THE FULL LIST HERE.

For decades, researchers just didn't understand why male funnel-web spiders had evolved to poison humans above all other vertebrates — especially since humans are not their natural predators.

"It has puzzled scientists why these toxins are so deadly to humans, when they and other primates, haven't featured as either prey or predator during the spider's evolution," Bryan Fry, associate professor at the University of Queensland, said in a statement at the time.

"And we couldn't understand why most human deaths were being caused by male funnel-web spiders, which seemingly had much deadlier venom than females."

But after conducting their experiment, the researchers have a better grasp of the method behind the deadly madness.

Through genetic sequencing, the researchers discovered that this is all "an unfortunate evolutionary coincidence."

A female funnel-web spider. The researchers found male funnel-web spiders were more lethal to humans.

Humans were never the primary target of the funnel-web spider's venom. The venom evolved to target other vertebrates — birds, lizards, and so on — and just happened to kill humans, too.

Male funnel-web spiders also are more likely to kill with their venom due to evolutionary adaptations, according to the researchers. They are more likely than females to wander long distances in search of mates, encountering predators along the way.

Ultimately, there may be a silver lining to this weird and awful trait: The unique susceptibility of humans to funnel-web spider venom could yield new insights in medical treatment or the development of insecticides, the researchers concluded.

For the time being, however, we are still at the mercy of this remarkably lethal Aussie creature.

INVERSE IS COUNTING DOWN THE 20 STORIES THAT MADE US SAY 'WTF' IN 2020. THIS IS NUMBER 16. READ THE ORIGINAL STORY HERE.

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