Ammonite fossil from Madagascar

Nature's secret code. Fibonacci Day

Look closely at this ammonite fossil. Its swirling shell, once home to a prehistoric sea creature, holds a mathematical secret—a spiral pattern. Each new chamber is proportionally larger than the previous one, maintaining a consistent growth ratio, often associated with the Fibonacci sequence.

Each November 23, we celebrate Fibonacci Day, named after the 13th-century Italian mathematician Leonardo Bonacci (Fibonacci), who introduced the concept to Europe. The pattern 1, 1, 2, 3, 5, 8…—where each number is the sum of the two before it—was, however, first described in India as early as 200 BCE by the ancient poet-mathematician Pingala. The Fibonacci sequence appears widely in nature, including pineapples, artichokes, pinecones and the arrangement of leaves on a stem.

Ammonites were molluscs that lived between 400 and 66 million years ago, gliding through ancient seas inside coiled shells that protected their soft bodies. When ammonites perished, sediment buried their shells and minerals slowly turned them to stone, preserving this natural geometry for millions of years. Today, the ammonite fossil is a striking reminder that math and nature speak the same language.