Plants, dating back a staggering 470 million years, have long fascinated scientists with their intricate patterns and structures. Among the enigmatic features found in nature, Fibonacci spirals have captivated researchers for centuries. Named after Leonardo Fibonacci, the renowned Italian mathematician, Fibonacci spirals have been believed to be an ancient and unchanging trait in plants. However, a groundbreaking new study is shaking the foundations of this long-held belief by examining a 407-million-year-old fossilised plant.
Led by Holly-Anne Turner, a Paleontology Ph.D. student at University College Cork (UCC), the team of researchers embarked on a journey to explore the spirals in the leaves and reproductive structures of this ancient plant. Turner’s fascination with the topic began during her undergraduate years at the University of Edinburgh, setting the stage for this remarkable investigation.
The mathematical basis for Fibonacci spirals is the Fibonacci sequence, a series in which each number is the sum of the two preceding numbers. The spirals are created by sketching arcs from a centre point and expanding outward in circles that follow the Fibonacci sequence. They can be found all over nature, from the arrangement of sunflower seeds to the intricate patterns of pine cones.
Fibonacci spirals were thought to be a universal property present in the oldest plants on Earth, according to conventional science. However, the team’s study challenges this notion through the examination of the Asteroxylon mackiei, a fossilised plant discovered in a Scottish sedimentary near Aberdeen known as the Rhynie Chert. This ancient plant, belonging to the earliest group of leafy plants, provided a unique opportunity to delve into its reproductive structure and leaf arrangements.
Using advanced 3D reconstruction techniques, the team collaborated with digital artist Matt Humpage to recreate accurate models of the Asteroxylon mackiei through 3D printing and digital rendering. By analysing the arrangement of lateral organs, such as leaves and reproductive structures, along the stem of the plant (known as phyllotaxis), the researchers made a surprising discovery.
Contrary to earlier conceptions, the Asteroxylon mackiei leaf arrangement revealed distinct non-Fibonacci spirals, throwing doubt on the premise that Fibonacci spirals were uniformly present in early plant species. This discovery shows that different plant groupings may have had different evolutionary routes in terms of leaf spirals.
This study has far-reaching ramifications. While the precise explanation for the abundance of Fibonacci spirals in modern plants is unknown, several scientists suggest that these spirals maximise packing efficiency and optimise seed sunshine exposure. Understanding early plant growth patterns and evolutionary trajectories is critical to unravelling the riddles of plant life on Earth today.
This remarkable study calls into question long-held ideas and emphasises the importance of continuing to explore and study ancient flora. Scientists are uncovering the extraordinary intricacy and diversity that have moulded the natural world for millions of years as they probe deeper into the evolutionary history of plant structures. The 400-million-year-old fossil provides an extraordinary insight into the past, motivating more research and increasing our understanding of the genesis of Fibonacci spirals in plants.