Where did the heart shape come from?

If two swans like 'kiss' theire heads come togheter and make the shape of a heart. That's what I think it comes from.

In European traditional art and folklore, the heart symbol is drawn in a stylized shape. This shape is typically colored red, suggesting both blood and, in many cultures, passion and strong emotion. The hearts have constituted, since the 15th century, one of the red suits in most playing card decks. The shape is particularly associated with romantic love; it is often seen on St. Valentine's Day cards, candy boxes, and similar popular culture artifacts as a symbol of romantic love. What the traditional "heart shape" actually depicts is a matter of some controversy. It only vaguely resembles the human heart. Some people claim that it actually depicts the heart of a cow, a more readily available sight to most people in past centuries than an actual human heart. However, while bovine hearts are more similar to the iconic heart shape, the resemblance is still slight. The "heart" shape could also be considered to depict features of the human female body, such as the female's pubic mound or spread vulva. The tantric symbol of the "Yoni" is another example of a heart-shaped abstraction of a woman's vulva. In the introduction to The Vagina Monologues Gloria Steinem writes, "[The heart] was reduced from power to romance by centuries of male dominance." Others maintain that the heart resembles the shape of the female breasts or the female buttocks Another possible origin can be seen on the coins of the ancient city of Cyrene, some of which depict the seeds or fruit of the now-extinct silphium plant. The seeds are distinctly heart-shaped. Since this plant was widely used as an ancient herbal contraceptive or abortifacient, this shape may have come to be associated with sexuality and love

In the 12th-16th centry (The time where it is believed the origin of the heart shape occurred) It is said the "Heart Shape" (not actually refereed to as a "Heart" at this point) was at the earliest known point the image of two Ivy/Fig leaves overlapping.