Crop circles: Art of alien signs?

Crop circles in China for the past 3000 years?

2001 Eyewitness account in Holland

1999 Milk Hill season opener.

1991 Barbury Castle tetrahedron.

1997 Henwood Down ant.

1998 Beckhampton double pentagram.

1998 Weyhill circle and ring.

1998 East Field heptagon.