The tradition of wedding rings originated in ancient Egypt. Egyptians used to make rings out of marsh grass which was braided into rings and worn by women.
The Romans refined the tradition by using iron instead of marsh grass to make thrings. They also started the fashion of engraving wedding rings.
Later, during Christian ceremonies the wedding ring became a highly decorated band, on which doves or two linked hearts were often etched. At some point the Church started seeing this as a pagan expression so all rings were considerably simplified and adopted a cleaner look.