The existence of a crashed starship in the Barrier Peaks? Evidence. Place names across Greyhawk that sound kind of Belgian-Flemish? Evidence.
Here's what is going to happen to us, so be prepared.
Dutch scientists create lightless agriculture.
Meeuws and three other Dutch bioengineers have taken the concept of a greenhouse a step further, growing vegetables, herbs and house plants in enclosed and regulated environments where even natural light is excluded.
Mind-flayer starship (we know they do this - witness the Barrier Peaks) flies close to Earth and destroys civilization with radiation and stuff to turn it into a cattle-planet, only they miss Belgium, Switzerland and the Netherlands, probably because of the Alps being in the way. It has already done its scouting pass.
A small near-Earth asteroid (NEA), discovered Monday night by the NASA-funded LINEAR asteroid survey, will make the closest approach to Earth ever recorded. There is no danger of a collision with the Earth during this encounter.
The object, designated 2004 FH, is roughly 30 meters (100 feet) in diameter and will pass just 43,000 km (26,500 miles, or about 3.4 Earth diameters) above the Earth's surface on March 18th at 5:08 PM EST (2:08 PM PST, 22:08 UTC).
Obviously this was only a scoutship, because there aren't enough ten-foot squares in a ship that's only 100ft in diameter. The big ship is lurking out there, though.
Also, all that spacewar stuff is going to change the geography around, which is why Belgium and Switzerland end up on the Eastern Coast of a continent instead of a Western Coast. So, the bombardment is going to be really bad if it makes water and land switch places. We can deduce this, though, from the map of Greyhawk, and we know we are Greyhawk because of this Dutch underground agriculture thing. It follows perfectly.
Basically the only radiation effects on the Dutch are going to be those pointy ears, but some of them are so radiation-burned that their skin turns black, and it's a heritable trait, which is enough to make some of them say, "Screw this, we're going under the ground, (which used to be a sea hereabouts), and be safe from the radiation." The other Dutch that only got the pointy ears are more sanguine about their chances on the surface, but just in case they do what anyone would do, and try to stay in the shade as much as possible, which means disappearing into the forests. Duh. They're the elves. That's why no one can speak Elvish: it's Dutch.
Meanwhile, in Switzerland, people just become really short from the radiation GNOMES OF ZURICH! only the foreshadowing is wrong and they are dwarves instead. It's natural for echoes of the future to be wrong. Gnomes probably come later. The Swiss origins of the Dwarves explain the whole "we like gold" thing, and suggests that the Monster Manual omitted the fact that dwarves probably like chocolate. Gnomes probably come from interbreeding between the Swiss and the Dutch, I guess.
The rest of the world is like Gamma World for a while, only there is a lot of natural selection going on because of the mind-flayers treating everyone like brain-cattle. Because of the natural selection we get spells, with which we start pummeling the mind-flayers until the mind-flayers say, "Screw this, we're going underground with the Dutch because we have diodes too."
Which basically leaves the surviving humans out there with the mutants (goblins and rust monsters and things like that), except for the Dutch living in the shade of the forests and a bunch of short Swiss bankers tunneling around madly in the Alps until they decide to diversify into some other mountain chains and end up pretty much all over the place.
Get ready everyone. Greyhawk is coming.
(Next up: results of the Great Greyhawkization on various bloggers)