It is suspect that crop circles seem to have arisen only when we got our hands on computer technology, and there is a black box budget for a whole outer-space military-industrial-nerdtopia complex, dithering every which way. But, it could also be true that aliens didn't think to communicate with us until we became this, ehem, advanced. I.e., question is moot or debatable.
But, the following two articles from "fake news" sources do fulfill my top hypotheses about crop circles. I want you to note that, recently, scientists have managed to quantum-entangle 1 million particles. That is as many neurons as are in an intelligent bee's head. Scientists have also telecommunicated via entanglement across thousands of miles. And, a useful way to do such is via biological entities.
That means that the cross-universe, i.e., cross-time, entanglement manipulation of crop DNA and processes, is probably entirely possible. What I, myself, cannot figure out is how they might so-specifically geo-locate. But, yes, crop circles are very possibly messages from aliens and/or the future. Another reason why I believe this is possible is because I have studied many crop circles, and found apparent messages. Some have been so complex that they seem to have been beyond human origin. I am not talking confusedly complex. I am talking deciphered complex. I really think this is something spectacular. (Acknowledged: Many crop circles are human creations). Check out the pretty pictures:
Crop Circles – Messages from Another World?
Scientist claims CROP CIRCLES are ‘ALIEN messages from the future’