Are crop circles a human creation

I saw on a documentary about how it is too hard for humans or human equipment to make crop circles. They made it out like it's humanly impossible and the only answer is aliens.

What do you think?

Here's some photos of the latest crop circles:
http://www.realufos.net/2008/08/avebury-…

Yeah, we can make microchips and nanotechnology and build skyscrapers, but we can't knock down some plants. Here's another great crop circle. I think you'll have trouble claiming this one is thanks to aliens.

http://blog.skepticview.com/wordpress/?p…

Did aliens leave the milk out too?

Use the "Summer rule" - Summer man-made, summer unknown. Actually, SOME crop circles have interesting characteristics that cannot be duplicated by guys with a rope & a board. For instance, some are more radioactive than the surrounding terrain. In some of them the plants appear to have been bombarded with microwave radiation, and other unique characteristics. Often the plants are NOT broken, as they are with someone with a rope and a board. Sometimes the earth has materials which do not occur in nearby dirt... What causes them? I dunno, maybe some kind of vortices or...? But all I'm certain of is that not ALL were made by fakers.

We know that the most well-known crop circles (the ones considered too difficult for humans to do) were done by humans (and only two guys, at that).

Therefore, that must have been yet another documentary that is trying to get you to accept something that is even more fooling than reality, just by telling you that reality is impossible.

why do they come and make stupid circles and not visit the bars or the movies,or the beach,its just like big foot myth,where is he hiding for so long,they use wooden/metal boards to make the grass lay down,notice there is always a path to the circle,