Around 90% of all humans prefer to use their right hand. For cockatoos, it’s mostly the left.
The ancient marine creature Spriggina floundersi didn’t have hands. It barely had a head. And yet we now know it also had a dominant side of its body.
A US study comparing 76 fossils from Nilpena Ediacara National Park in South Australia and the South Australia Museum suggests a bias in how they moved, one that favored movements to the right over bends to the left.
This twist doesn’t seem to be the result of differences in preservation, nor a quirk of anatomy, leaving the small team of researchers behind the study to conclude it’s an early sign of behavioral handedness.
“When we talk about being right-or-left-handed, most people likely think about how they hold a pencil or kick a soccer ball,” says lead author Scott Evans, assistant curator of invertebrate paleontology at the American Museum of Natural History.
“But our research shows that an animal without hands or feet, living over 500 million years ago, may have had its own version of handedness.”
S. floundersi is no stranger to paleontologists. An early form of complex life, it emerged in a period of diversification known as the Ediacaran (635 to 538 million years ago), and was one of the earliest examples of an animal with bilateral symmetry.
Its inch-long, ovoid body was segmented and tapered, making it one of the first organisms with a shape reminiscent of a head and tail.
Whether the blunt, U-shaped end truly leads the way, we can only presume. With nothing else to go on but fossils, researchers are left to compare the contortions of their bodies to judge their behavior.
Of the 100 fossils Evans and his team collected for the study, 76 had sufficiently detailed measurements for an analysis, and around 70% of those had bodies that were kinked in a clear direction. And of those, there were twice as many left bends as right.
Since the fossils are mirror impressions of their original bodies, the findings suggest individual S. floundersi favor turning right over turning left.
A wide variety of animals living today have a preference for using a particular side of their body or direction, considered in many cases to be a consequence of task-division in a complex brain.
Learning that the first known head had a preference for one direction over the other suggests its nervous system may have already had an architecture similar to that of modern creatures.
“It’s a reminder that some of the traits we take for granted today have incredibly ancient origins,” says University of California paleontologist Mary Droser.
This research was published in the journal Scientific Reports.
Source: American Museum of Natural History
Fact-checked by Bronwyn Thompson
