Researchers from the University of Cambridge and Helmholtz-Zentrum Berlin have found what they describe as the earliest evidence of an internal navigation system in animals. The study centers on tiny magnetic fossils, called ‘magnetofossils’, dating back 97 million years and discovered in ancient seafloor sediments. These structures are believed to be biological, but their origin and purpose had been unclear.
Using a new imaging technique developed at the Max Planck Institute and applied at the Diamond X-ray facility in Oxford, the research team captured three-dimensional images of the fossils’ magnetic structure for the first time. Their findings show that these magnetofossils contain features optimized to detect both the direction and strength of Earth’s magnetic field—properties that would aid navigation.
“Whatever creature made these magnetofossils, we now know it was most likely capable of accurate navigation,” said Professor Rich Harrison from Cambridge’s Department of Earth Sciences, who co-led the research.
The results provide direct evidence that animals may have used Earth’s magnetic field for navigation as far back as 97 million years ago. This ability, known as magnetoreception, is still seen today in birds, fish, and insects. However, how modern animals use this sense remains under investigation.
Harrison explained that while certain bacteria use chains of small magnetic particles to orient themselves in water columns, the studied magnetofossils are significantly larger—10 to 20 times bigger than those found in bacteria—and were collected from a site in the North Atlantic Ocean. Some scientists had previously suggested these large structures might serve other functions like protective spines. Model simulations pointed instead to advanced magnetic properties.
“It looks like this creature was carefully controlling the shape and structure of these fossils, and we wanted to know why,” Harrison said.
The internal images revealed swirling patterns formed by “magnetic moments” inside each fossil—a tornado-like vortex configuration thought to make them sensitive to both latitude (the tilt) and longitude (the strength) of Earth’s magnetic field. According to Harrison: “This magnetic particle not only detects latitude by sensing the tilt of Earth’s magnetic field but also measures its strength, which can change with longitude.”
Such stability could help an organism resist environmental disturbances during migration over long distances. “If nature developed a GPS, a particle that can be relied upon to navigate thousands of kilometres across the ocean, then it would be something like this,” Harrison added.
While researchers do not yet know which animal produced these fossils, Harrison suggests migratory eels could be candidates because they evolved around 100 million years ago and undertake extensive migrations using some form of geomagnetic sense.
“This was a truly international collaboration involving experts from different fields, all working together to shed light on the possible functionality of these magnetofossils,” said Sergio Valencia from Helmholtz-Zentrum Berlin.
Despite uncertainty about their exact source organism, Harrison stated: “Giant magnetofossils mark a key step in tracing how animals evolved basic bacterial magnetoreception into highly-specialised, GPS-like navigation systems.”
The research received support from several European funding bodies including the European Union and Royal Society. Professor Rich Harrison is a Fellow at St Catharine’s College, Cambridge.
Reference:
Richard J. Harrison et al., ‘Magnetic vector tomography reveals giant magnetofossils are optimised for magnetointensity reception.’ Communications Earth & Environment (2025). DOI: 10.1038/s43247-025-02721-3