Ancient "Magnetofossils" Reveal a Prehistoric Internal GPS — Evidence of Magnetic Navigation 97 Million Years Ago

Researchers report evidence that ancient marine animals used Earth's magnetic field to navigate. Scientists from Cambridge University and Helmholtz-Zentrum Berlin used a new magnetic-tomography technique to peer inside unusually large "magnetofossils" preserved in ocean sediments dated to about 97 million years ago. The internal magnetic arrangements are consistent with biological magnetoreception — a GPS-like sense that many modern animals use to navigate.

What the team found

The fossils contain organized magnetic structures whose orientation and arrangement match patterns expected from magnetoreceptive organs. These tiny magnetic domains arise from the magnetic moments of electrons and, when aligned in particular ways, can serve as internal compasses. Mapping those internal fields gives direct physical evidence that the fossilized structures were capable of sensing Earth's magnetic field.

How they looked inside

Standard X-rays struggled to penetrate the outer layers of these larger fossils, so co-author Claire Donnelly (now at the Max Planck Institute) developed a refined imaging approach based on magnetic tomography. Using her method at the Diamond Light Source facility near Oxford, the team reconstructed the fossils' internal magnetic architecture without relying solely on conventional radiography.

Rich Harrison, co-leader of the study from Cambridge’s Earth Sciences Department, said: "Whatever creature made these magnetofossils, we now know it was most likely capable of accurate navigation."

Claire Donnelly added: "Mapping the internal magnetic structure with magnetic tomography was already a major step, and that it tells us something about navigation millions of years ago is truly exciting."

Jeffrey Neethirajan, a Ph.D. student in Donnelly’s lab, commented that it was gratifying to apply the method to natural samples for the first time and obtain clear, interpretable results.

Who made the magnetofossils?

The researchers cannot yet identify the exact species that produced the magnetofossils. The specimens were abundant enough to suggest a common migratory organism, and the team proposes migratory candidates — for example, ancestral eels — which fossil and molecular evidence indicate emerged roughly around 100 million years ago. Further fossil and ecological searches will be needed to pinpoint the creators.

Why it matters

These findings provide some of the earliest direct physical evidence of magnetoreception in animals and help bridge the gap between simple bacterial magnetite sensors and the specialized navigation systems seen in birds, sea turtles and other migratory species today. The study was published in Nature on Oct. 20.

Sources and credits: Study co-leaders and co-authors include Rich Harrison (Cambridge), Claire Donnelly (Max Planck Institute), and collaborators at Helmholtz-Zentrum Berlin and the Diamond Light Source facility. The original research paper appeared in Nature on Oct. 20.