The history of the bridesmaid varies across cultures, religions and time periods. In early Roman times, bridesmaids formed a kind of bridal infantry as they accompanied the bride to the groom's village. This "protective shield" of similarly outfitted bridesmaids was supposed to intervene if any wayward thugs or vengeful suitors tried to hurt the bride or steal her dowry.
The Western bridesmaid tradition seems to have originated from later Roman law, which required ten witnesses at a wedding in order to outsmart evil spirits believed to attend marriage ceremonies. The bridesmaids and ushers dressed in identical clothing to the bride and groom, so that the evil spirits wouldn't know who was getting married.
According to Anglo-Saxon history, the groom kidnapped his bride in order to get married. The original best man, or the groom's warrior friend, helped the groom fight off other men while "bridesmen" or "bridesknights" made sure the bride arrived safely to the ceremony.
and to think, we don't get to do any of that fun stuff these days...