The heart shape has been used as a symbol for centuries and its meaning has evolved over time.

One of the earliest known uses of the heart symbol was by the ancient Egyptians, who used it to represent the heart of the deceased during the mummification process. The heart was believed to be the center of the soul, and it was thought that preserving the heart would allow the soul to live on after death.

It's believed that the heart symbol was first associated with love in the Middle Ages. The heart shape was often used in literature and art to represent love and passion. It was also used as a symbol of devotion and loyalty in heraldry. 

The 'scalloped' shape of the heart symbol we know today began to be used in the early 14th century, for example, in the miniatures in Francesco da Barberino's Documenti d'amore shown above.

Today's heart shape became widely accepted in the 19th century and continues to represent love and affection.