As writing deadlines approach, it's common to find Geek contributors collapsed onto the floor, curled up into a tight ball.
Sometimes they cry out to a god who has forsaken them, but often they simply lay there silently, in fetal position, rolled up like a woodlouse. This “curl into a ball” strategy doesn’t work very well for humans, but for some terrestrial crustaceans, insects and sea creatures it’s a very effective defense mechanism. Fossil hunters at Cambridge University think they’ve found one of the first creatures to adopt this behavior, and the animals did it a long, long time ago.
Paleobiologist Javier Ortega-Hernández was examining fossils originating in Canada when a tiny trilobite from a group called Olenellida caught his eye. It looked as though spines were protruding from its head, but microscopic inspection showed the spines were coming from its tail, which had been tucked under its body.
Trilobites were a large and very diverse group of marine invertebrates first appearing during the early Cambrian around 520 million years ago. This was a time of great evolutionary experimentation, with predator and prey evolving weapons, hard shells and strategies needed for survival. Some of the genetic groundwork laid down during this era is conserved in modern animals to this day. Although curling into a ball has evolved independently many times, such as with pangolins and hedgehogs, Ortega-Hernández says his little trilobite predates the earliest known example by millions of years.
“Our discovery sheds light on one of the longest evolutionary arms races in the history of animals,”
This ancient animal had not quite mastered the art of curling up since many parts of its body were still exposed. It simply did the best it could given its body plan. Eventually, some trilobites did evolve a body structure allowing them to roll up tightly and securely, helping them exist on Earth for an amazing 270 million years.
One obvious question is whether the Ortega-Hernández trilobite was actually trying to curl up when it died, or was simply squashed into that position. Ortega-Hernández addressed that question:
“If the body was clearly broken, twisted, bent in odd ways, or otherwise deformed, we would be very suspicious.”
But this animal was curled up with perfect symmetry, with all body parts correctly articulated just like modern examples of animals that curl up.