Fossils dating back 443 million years are shedding light on the evolution of early vertebrate eyes, revealing remarkable advancements in their structure that challenge previous assumptions about vertebrate development.
A team of scientists from The University of Manchester has made a groundbreaking discovery by investigating ancient fossils found in Scotland. These fossils provide rare insights into an often-overlooked chapter in evolutionary history since the early vertebrates had soft bodies, making their remains notoriously difficult to analyze due to their fragility and incompleteness.
Utilizing cutting-edge technology at the Stanford Synchrotron Radiation Lightsource (SSRL) located at SLAC National Accelerator Laboratory in California, researchers meticulously examined two small jawless fish species, Jamoytius and Lasanius, discovered near Lesmahagow, south of Glasgow. With this innovative synchrotron particle accelerator, they were able to map the chemical components within these fossils, marking a significant leap forward in our comprehension of the initial phases of vertebrate evolution.
Roy Wogelius, a Professor of Geochemistry at The University of Manchester and one of the study's leaders, expressed excitement over the results: "We aimed to investigate transitional fossils from early vertebrate evolution using our advanced methods. What we uncovered exceeded our expectations; not only did we identify primitive bone structures in the geological record, but we also captured unprecedented images of some of the oldest camera-like eyes. These eyes even retain the small notch where the optic nerve was connected, highlighting features that laid the groundwork for modern vertebrate vision."
Adding to this enthusiasm, researcher Dr. Jane Reeves from the same university remarked, "It's astonishing how much new information can be extracted from fossils that are typically too poorly preserved for traditional analysis, thanks to these advanced technologies. Our findings help settle scientific debates that have persisted since the Victorian era, indicating that bones and eyes originated much earlier in vertebrate history—possibly even before the group as a whole emerged.
"I’m particularly thrilled because these fossils likely belong to the ancestors of contemporary lampreys and hagfish, which currently lack many of these features. This adds to the growing body of evidence suggesting that these organisms have a far more intricate evolutionary past than previously recognized."
The technique used, known as Synchrotron X-ray Fluorescence imaging, involves scanning samples with a powerful X-ray beam produced by the synchrotron accelerator. This process prompts atoms within the sample to emit their own distinctive X-rays—known as X-ray fluorescence—which can then be detected by the scanning system. The specific properties of these fluoresced X-rays correspond to the chemical elements from which they originated, enabling researchers to identify and map minute chemical differences embedded in the fossils, including remnants of tissues that may no longer be visible under normal light.
Dr. Nick Edwards, a Staff Engineer for the X-ray Fluorescence Imaging beam lines at SSRL, highlighted the advantages of this method: "Synchrotron X-ray Fluorescence imaging is a flexible and effective approach for studying fossils. It doesn't require special environmental conditions, and we can analyze relatively large specimens without needing to remove material. We can detect incredibly low levels of elements present in biological systems, correlating them to specific fossil tissues within hours. The discoveries from these fossils are captivating and further affirm that the chemical signatures of extinct organisms can be preserved over extensive geological timescales, aiding our understanding of life's evolution."
In their research, the team identified traces of zinc and copper, which unveiled the structural features of the retina and pigment layer in these ancient eyes. Additionally, they found calcium and phosphorus, indicating the presence of early bone-like tissues.
This research has garnered international acclaim, with Dr. Pierre Gueriau from the University of Lausanne—who was not part of the study—stating, "This research not only revises parts of the evolutionary narrative regarding our early vertebrate ancestors but also showcases how advanced fossil imaging techniques extend beyond traditional CT scans. They encompass a variety of analytical chemistry methods capable of uncovering information previously thought lost to the fossilization process. Indeed, it’s an exciting time for paleontology."
Dr. Robert Sansom, a palaeobiologist at The University of Manchester and the corresponding author of the study, shared his enthusiasm: "I have a deep appreciation for these fossilized fish. Though they've been extinct for over 400 million years, they continue to astonish us with new insights into our distant origins."
The research team plans to continue employing this high-energy physics technology to extract chemical traces from other vertebrate fossils, which will provide essential insights into the evolutionary trajectories of various animals, including birds, dinosaurs, mammals, and even microbial life.
This pivotal research was published in the journal Proceedings of the Royal Society B under the title: "Early vertebrate biomineralisation and eye structure determined by synchrotron X-ray analyses of Silurian jawless fish."
For further details, you can access the publication directly here: DOI: 10.1098/rspb.2025.2248 (URL: https://doi.org/10.1098/rspb.2025.2248)
