Feb. 12 (UPI) -- New fossil evidence recovered from Gabon suggests organisms were mobile as early as 2.1 billion years ago. The next oldest evidence of motility dates to 570 million years ago.
Several years ago, Gabon's ancient deposits yielded the oldest evidence of multicellular life. Now, researchers have found evidence -- from the same geological deposit -- that these early complex organisms were on the move.
Paleontologists with the French National Center for Scientific Research found tube-like pathways crisscrossing the ancient rocks. The dimensions of the miniature tunnels were revealed by X-ray photography. Most of the tunnels measure a few centimeters in diameter and run through five distinct layers of sedimentary rock.
Chemical analysis of the ancient subway system suggests they are biological in origin and were created at the same time that the layers of sediment were deposited.
Evidence of ancient microbial biofilms are preserved between each sediment layer. The organisms that created the ancient tunnels, scientists hypothesize, may have been moving through soil to harvest the nutrients and dioxygen produced by the cyanobacteria.
Researchers can't say for sure what these ancient tunnel-diggers looked like. Their best guess is that the primitive species recalled colonial amoebae, with independent units forming slug-like clusters when resources turned scarce.
The latest findings -- detailed in the journal PNAS -- more than doubles the age of the oldest evidence of motility.
Previously, molecular clock analysis suggested mobility among multicellular organisms emerged 570 million years ago. Fossils confirmed the prediction, until now. The discovery of ancient sedimentary tunnels in Gabon raises new questions about the evolution of early life.
"While it remains uncertain whether the amoeboid-like organisms represent a failed experiment or a prelude to subsequent evolutionary innovations, they add to the growing record of comparatively complex life forms that existed more than a billion years before animals emerged in the late Neoproterozoic," researchers wrote in their paper.