A wishbone, scientifically known as the furcula, is a forked bone found in most birds and some non-avian dinosaurs. This V-shaped or U-shaped bone is located in front of a bird’s breastbone, or sternum. It is formed by the fusion of two clavicles, which are comparable to the collarbones in humans.
Anatomy and Biological Role
The furcula is positioned between a bird’s shoulders, articulating with the scapulae, or shoulder blades. This bone works as a strut, resisting compression along its length. In conjunction with the coracoid and scapula, it forms the triosseal canal, which contains a strong tendon connecting muscles to the humerus for lifting wings during the recovery stroke.
The primary function of the furcula is to strengthen the thoracic skeleton, enabling it to withstand forces encountered during flight. During the downstroke of a bird’s wings, powerful flight muscles compress the lower part of the furcula, causing its arms to spread apart, sometimes expanding by as much as 50% of its resting width. This action allows the furcula to behave like a spring in the pectoral girdle.
As the wings move upward, the furcula snaps back to its original position, releasing stored energy. This spring-like mechanism assists in the upstroke of the wingbeat cycle and helps draw the shoulders toward the body’s midline. The furcula also aids respiration by helping to pump air through the bird’s air sacs, facilitating the exchange of gases during flight. Its flexibility and springiness are considered significant for the mechanics of flight in many avian species.
The Cultural Tradition
Breaking a wishbone, often from a chicken or turkey, is a cultural tradition. Typically, two people pull on either end of the dried bone until it breaks. The person with the larger piece is traditionally believed to have their wish granted.
This custom originated with the ancient Etruscans in Italy, who regarded birds as oracles. Early Etruscans would dry the furcula of slaughtered chickens and stroke the bone while making wishes. Romans later adopted this practice, and as wishbone demand grew, they began breaking them, allowing more people to participate in the ritual.
The tradition spread to England and the Americas, becoming associated with holiday meals, particularly Thanksgiving. An older name for the wishbone, particularly in Britain, was “merrythought,” used until the early 1900s. This term referred to the pleasant thoughts or anticipations associated with the bone-pulling ceremony.