Has there ever been an exact date as to when CCs became so complex?
I would venture that there have been several (hundred??) examples quoted on this site alone about "The Megalithic Yard"...so would the ability to calculate this come under geometry and proportion
One corn circle maker on The One Show last week didn't have Thom's "Megalithic Yard" stick but had instead "The Corn Circle Plank" a 4 foot length of 4 X 2. he reckoned pretty much every dimension on every corn-circle in the UK could be measured by it. It was all he'd ever used along with a plan and a length of rope.