Imagine a world where the earliest animals were as soft as jelly, leaving no trace of their existence in ancient rocks. This is the groundbreaking revelation from a team of Bristol scientists who have finally solved a long-standing mystery about the evolution of sponges, Earth’s most ancient animals. But here’s where it gets controversial: their findings challenge the fossil record, suggesting sponges evolved at least 650 million years ago—a full 100 million years before the oldest known sponge fossils. How is this possible? And this is the part most people miss: the first sponges were soft-bodied, lacking the mineralized skeletons we associate with them today. This means there were no spicules—those tiny, glass-like needles—to fossilize, leaving scientists scratching their heads for decades.
In a study published on January 7, 2026, in Science Advances, Dr. M. Eleonora Rossi and her international team from the University of Bristol’s School of Biological Sciences cracked this puzzle using a two-pronged approach. First, they combined genetic data from 133 protein-coding genes with fossil evidence to create a new timeline for sponge evolution, dating their origin to between 600 and 615 million years ago. Second, they uncovered that sponge skeletons evolved independently in different groups, a finding that flips our understanding of early animal life on its head.
But why does this matter? Sponges are not just simple sea creatures; they are the first lineage of reef-building animals and possibly the earliest animal group to evolve. Understanding their history offers a window into how life and Earth co-evolved, shaping the planet for more complex life forms—including us. Dr. Rossi explains, ‘The first sponges were soft-bodied, which is why we don’t find spicules in older rocks—they simply didn’t exist yet.’ This revelation not only reconciles genetic and fossil evidence but also raises a tantalizing question: if not skeletons, what drove early sponge diversification?
Dr. Ana Riesgo, a leading sponge expert from Madrid, adds, ‘Modern sponge skeletons may look similar, but their construction is wildly different. Some use calcite, like chalk, while others use silica, essentially glass. Even their genomes tell a story of independent evolution.’ To map this evolutionary journey, the team employed a Markov process—a predictive model used in finance and AI—to trace transitions between skeletal types, including soft-bodied forms. The results were clear: the idea that early sponges had mineralized skeletons is highly unlikely.
But here’s the controversial part: If sponges didn’t rely on skeletons, what gave them the edge to thrive and diversify? Professor Phil Donoghue hints at a mystery yet to be solved, ‘Early sponge evolution was driven by something entirely different, and we’re still piecing that together.’ Professor Davide Pisani takes it a step further, ‘This isn’t just about sponges. It’s about the origins of reef systems and how early animals transformed our planet.’
So, what do you think? Does this study rewrite the history of animal life? Or does it open more questions than it answers? Let us know in the comments—this debate is far from over.
