No, there's no proof whatsoever that the curricks are prehistoric. In the conventional sense. It's darn obvious though, with an open mind, in the right landscape. I spoke to an old lady this morning - she looks out onto six curricks on the skyline. "That's the first time I've heard their name and I've lived here fifty one years". I've found a new standing stone, just a metre high and usually lost in the bracken. (If you go to the Kirkhaugh stone circle with Hob please follow my instructions for getting to it to the letter, please. There's a kindred imago here - http://www.cropcircleconnector.com/2005/bishopsutton/suttonbishop2005a.html)