Animals like birds and sea turtles navigate using a “biological GPS” called magnetoreception. We now actually know that many animals use this method to connect with Earth’s magnetic field so they know where to go — but scientists don’t really understand how the whole process works yet.
As such, researchers at Cambridge University and the Helmholtz-Zentrum Berlin have been studying tiny ancient fossils littering ocean floors to learn more about magnetoreception. And sure enough, the team says they’ve discovered that these “magnetofossils” indeed exhibit magnetoreception. Because they found the magnetofossils in sediments that date back 97 million years, their work could be the first time we’ve had direct evidence that animals have been navigating the world like this for a very long time.
“Whatever creature made these magnetofossils, we now know it was most likely capable of accurate navigation,” Rich Harrison of Cambridge’s Earth Sciences Dept., and research co-leader, said in a statement.
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A new way of sensing
The researchers used a new technique that relies on magnetic tomography — a way of visualizing the internal structures of objects using magnetic fields. Previously, scientists had trouble looking inside larger magnetofossils like the newly discovered ones because more standard X-rays were unable to penetrate the outer layers.
That’s why the study’s co-author, Claire Donnelly from the Max Planck Institute in Germany, developed this new technique to peer inside. Because the fossils are rather large compared to magnetic receptors used by bacteria, for instance, the researchers refer to them as “giant” magnetofossils.
“That we were able to map the internal magnetic structure with magnetic tomography was already a great result, but the fact that the results provide insight into the navigation of creatures millions of years ago is really exciting!” Donnelly said in the release.
The team used Donnelly’s technique at the Diamond X-ray facility in Oxford. They found that the arrangements of tiny magnetic fields generated by spinning elections — or magnetic moments, to be precise — pointed to magnetoreception in whatever animals these fossils came from.
“It’s fantastic to see our method being used for the first time to study natural samples,” Jeffrey Neethirajan, a Ph.D. student in Donnelly’s lab, said in the release.
The mystery creature
Oddly enough, while the team thinks these fossils signify navigation via magnetoreception, they don’t know what animals created them. “This tells us we need to look for a migratory animal that was common enough in the oceans to leave abundant fossil remains,” Harrison said.
Eels might be a good candidate, Harrion speculates, as they evolved around 100 years ago, and they’re able to navigate waterways across the globe.
“Giant magnetofossils mark a key step in tracing how animals evolved basic bacterial magnetoreception into highly-specialized, GPS-like navigation systems,” Harrison said.
A paper about the study was published in the journal Nature on Oct. 20.