We can say several things that increase our confidence.
First, crops did not exist before us.
But presumably the plants that we later cultivated (or something very like them) was. Savanna's of open grasses etc.
So not very helpful.
Second, we have about 6000 years of history with no mention of crop circles.
As I have found recently it depends on who you ask and how they interpret things (hmmm ... that sounds familiar from somewhere).
There are suggestions (I haven't corroborated them mind) that Ancient Egyptians mention something which could be crop circles, and there are 17th century books that appear to describe the circles in the crops (again I haven't dug that deep ... possibly all a pile of non-crop-related-farming-waste).
Third, ALL evidence of crop circles begins in the 70s and so we see crop circles as something less than 50 years old.
Not necessarily ...
Sorry, the evidence says with a very high degree of confidence that crop circles only existed since human pranksters.
Human pranksters have been about for several thousand years though ....
Same story, nudder verse.
We have evidence that crop circles are man made and modern only and no evidence of any other possible way they could be made.
The main thing that I have seen with this thread is that the rigour required for the evidence of human manufacture of crop-circles is far less than that demanded of creationist 'science' (and I include ID there -- possibly contentiously).
Does any other explanation simply exceed the credibility threshold for cultural reasons?
Why do we discount aliens?
Personally I cannot imagine why an alien would come all this way to draw a crop circle ... but then I cannot figure why people would (secretly in the night ... never taking credit for some beautiful art).
The likelihood of non-human intelligent life in the milky way is not small given the 200-400 milliard () stars that we estimate.
So (unless there is some very hard, objective evidence) why DO we discount aliens?
I would suggest that even if we had several independent witnesses saying they saw aliens drawing a crop circle whilst partying with a keg of their favorite tipple that the scientific community would discount it instantly and without evidence.
Arguments from incredulity are not acceptable in ides/theories that conflict against current scientific wisdom, so why can they be used to support the status quo?
I'm sorry but you are simply wrong.
The demands made on Creationists and Intelligent Design are actually no different than those placed on crop circles.
And you certainly should know better than your posts indicate.
Aliens are discounted until there is some evidence that there are aliens.
Fantasy is discounted because it is fantasy.
You even summed the reasoning up in this post when you said "We have evidence that crop circles are man made and modern only and no evidence of any other possible way they could be made."
It really is that simple.
Until the ID and Creationists present testable and verifiable evidence in support of the existence of their Creator and Intelligent Designer and a method/model for that critter to influence living things, there is simply nothing to consider.
Anyone so limited that they can only spell a word one way is severely handicapped!