Ancient Egyptians may have been one of the first populations to use barrier method-style birth control. There's evidence written in the Ebers Papyrus -- as far back as 1550 BCE -- of women using vaginal suppositories made with an acacia, date and honey paste as a way to avoid pregnancy.
Fibers such as wool or cotton would have been moistened with a mixture of acacia leaves, dates and honey and inserted similarly to a tampon. Crazy as it sounds, this suppository -- which when in place acted like a modern-day cervical cap -- was actually effective. The fiber would physically block sperm from entering the uterus, and honey would hold the contraceptive in place, but it's the acacia that gave this birth control device its contraceptive qualities. Recent studies of acacia (Acacia auriculiformis) find that when fermented, it contains lactic acids, or triterpenoid saponins (including Acaciaside-A and Acaciaside-B). Lactic acid negatively impacts sperm motility (the ability to successfully swim toward an egg), making this one of the first spermicides.