So they looked at dolls. Yep, that's right. Marie Antoinette was more than a leader of France in the late 18th century, she was the unanimously agreed upon leader of fashion the world over. And whenever Marie Antoinette appeared in a new style, her peeps would make miniature versions of it for dolls and send those dolls to every major port.
It may have taken two months, but those "fashion babies" arrived on our doorsteps and brought detailed examples from the Queen of Fashion into our lives. And so, though it moved at a snail's pace compared to our changes from season to season now, styles changed far more quickly than they had in centuries prior.
All thanks to prettily made up baby dolls. =)