In general, people are leery of spiders, even though we know that (in most cases) they can’t really hurt us.

It’s the legs, maybe. Or the scurrying. Not really sure.

Were the first spiders on Earth relatively small, like they are today? Or were they giant versions, like everything else prehistoric seems to be?

They first emerged on land around 400 million years ago, and were thick-waisted versions called trigonotarbids. They also lacked spinnerets, which are used to make silk, and had segmented abdomens.

One of the earliest fossils of a “proto-spider” dates back 380 million years. Named Attercopus fimbriunguis, it’s not a true spider because it’s silk glands aren’t spinnerets, but used to wrap eggs, line the burrow, or smother prey. It also had a whip-like tail, sort of like a scorpion.

A fossil found in Myanmar, named Chimerarachne yingi, dates to the Cretaceous period. It also has a tail and spinnerets, likely a cousin to the modern spider.

The oldest order of true spider is the Mesothelae, explains Dr. Russell Garwood.

“We have known for a decade or so that spiders evolved from arachnids that had tails, more than 315 million years ago.”

Ancient spiders had silk-producing organs under middle rather than their rear, and were ground-dwelling, with both spinnerets and a venom gland.

There are a few spider-ish fossils that have showed up, like the Idmonarachne brasieri, which has a segmented body and lacked spinnerets, or the Arthrolycosa wolterbeeki, which is a true spider that dates back to 310 to 315 million years ago.

Modern spiders live on every continent on Earth and thrive in almost every habitat. They’ve survived for more than 400 million years aren’t likely to die out anytime soon.

No matter how many we step on.

Thought that was fascinating? Here’s another story you might like: Why You’ll Never See A Great White Shark In An Aquarium