Fossil study sheds light on famous spirals found in nature

Newswise — Research reveals that the leaf configurations in ancient flora contrast with those of contemporary plants, challenging a widely accepted hypothesis concerning the genesis of a renowned mathematical structure observed in the natural world.

The results suggest that the organization of leaves into recognizable spirals, prevalent in present-day nature, was uncommon among the earliest terrestrial plants that inhabited the Earth's crust.

Conversely, the ancient plants were discovered to possess an alternative form of spiral, thereby refuting a longstanding theory regarding the evolutionary development of plant leaf spirals. This suggests that leaf spirals evolved along two distinct evolutionary trajectories.

From the expansive vortex of a hurricane to the intricate twists of the DNA double-helix, spirals are ubiquitous in nature, and many of them can be described using the renowned mathematical sequence known as the Fibonacci sequence.

Named after the Italian mathematician Leonardo Fibonacci, this sequence serves as the foundation for numerous efficient and breathtaking patterns found in nature.

Plants frequently exhibit spirals, with Fibonacci spirals comprising more than 90% of these patterns. Sunflower heads, pinecones, pineapples, and succulent houseplants all showcase these distinct spirals in their flower petals, leaves, or seeds.

The prevalence of Fibonacci spirals, often referred to as nature's secret code, in plants has puzzled scientists for centuries. However, their evolutionary origins have largely been overlooked and understudied.

Due to their extensive distribution, it has been widely assumed that Fibonacci spirals were an ancient characteristic that evolved in the earliest terrestrial plants and became highly conserved throughout the plant kingdom.

Nevertheless, the University of Edinburgh, leading an international team, has challenged this theory by uncovering non-Fibonacci spirals in a 407-million-year-old plant fossil. This discovery has effectively overturned the previous notion.

By employing digital reconstruction techniques, the researchers successfully generated the initial 3D models of leafy shoots from the fossilized clubmoss Asteroxylon mackiei, which belongs to one of the earliest groups of plants with leaves.

The remarkably well-preserved fossil was discovered at the renowned Rhynie chert fossil site, located in a sedimentary deposit near the village of Rhynie in Aberdeenshire, Scotland.

The Rhynie chert site harbors evidence of some of the earliest ecosystems on the planet, marking the period when land plants initially evolved and gradually began to colonize the rocky surface of the Earth, thereby rendering it suitable for habitation.

The findings unveiled that the leaf and reproductive structures in Asteroxylon mackiei were predominantly arranged in non-Fibonacci spirals, which are uncommon in contemporary plants.

This discovery revolutionizes scientists' understanding of Fibonacci spirals in land plants. It suggests that non-Fibonacci spirals were widespread among ancient clubmosses and indicates that the evolution of leaf spirals took two distinct paths.

The leaves of ancient clubmosses followed a completely separate evolutionary trajectory compared to other major plant groups existing today, including ferns, conifers, and flowering plants.

In collaboration with digital artist Matt Humpage, the team utilized digital rendering and 3D printing techniques to create a comprehensive 3D model of Asteroxylon mackiei. This extinct plant species, which ceased to exist over 400 million years ago, was brought back to life through their innovative approach.

The research, which was published in the journal Science, received funding from several sources, including UK Research and Innovation (UKRI), The Royal Society, and the German Research Foundation.

Additionally, the study involved researchers from various institutions, including University College Cork in Ireland, the University of Münster in Germany, and Northern Rogue Studios in the UK.

Dr Sandy Hetherington, an evolutionary palaeobiologist and the project’s lead at the University of Edinburgh, said:

"Our 3D model of Asteroxylon mackiei allows us to analyze leaf arrangement in three dimensions for the first time. The ability to 3D print a plant fossil that is over 407 million years old and physically hold it in your hand is truly remarkable in terms of technological advancement."

“Our findings give a new perspective on the evolution of Fibonacci spirals in plants.”

Holly-Anne Turner, who contributed to the project as an undergraduate student at the University of Edinburgh and serves as the first author of the study, expressed her thoughts on the matter.

“The clubmoss Asteroxylon mackiei is one of the earliest examples of a plant with leaves in the fossil record.

-Anne Turner, the first author of the study and an undergraduate student at the University of Edinburgh, stated, "By utilizing these reconstructions, we were able to trace the individual spirals of leaves around the stems of these 407 million-year-old fossil plants. Our examination of leaf arrangement in Asteroxylon indicates that early clubmosses evolved non-Fibonacci spiral patterns."