A recent study has unveiled what is thought to be the earliest known evidence of an evolutionary arms race within the fossil record. Dating back 517 million years, these predator-prey interactions took place in ancient oceans, specifically in an area now known as South Australia. They involved a small shelled creature that shares a distant relation with brachiopods and an unknown marine animal adept at breaking through its shell.
A recent investigation, spearheaded by scientists at the American Museum of Natural History, has revealed what is considered to be the longest-standing example of an evolutionary arms race documented in the fossil record. These interactions between predators and prey, which occurred 517 million years ago in what is now South Australia, involved a tiny shelled organism that is distantly related to brachiopods and an unidentified marine predator skilled in puncturing its shell. This groundbreaking research is detailed in the journal Current Biology, marking the first clear evidence of such an arms race during the Cambrian period.
“Predator-prey dynamics are often highlighted as a key factor behind the Cambrian explosion, particularly concerning the swift rise in the diversity and numbers of organisms that developed hard shells. However, there has been a lack of concrete evidence illustrating direct responses from prey to predation, and vice versa,” explained Russell Bicknell, a postdoctoral researcher in the Museum’s Division of Paleontology and the study’s lead author.
An evolutionary arms race involves a continuous cycle where predators and their prey adapt and evolve in response to one another. This concept is often referred to as an arms race, as the improvements in one species compel the other species to enhance its own abilities.
Bicknell and his colleagues from the University of New England and Macquarie University in Australia examined a substantial range of fossilized shells belonging to an early Cambrian tommotiid species named Lapworthella fasciculata. They discovered over 200 tiny specimens, each measuring slightly larger than a grain of sand to just under the size of an apple seed, featuring holes likely created by a predatory organism, presumably a type of soft-bodied mollusk or worm. The researchers investigated these specimens in relation to their geological age, observing a correlation between an increase in shell wall thickness and a rise in the number of perforated shells within a brief time frame. This pattern suggests the presence of a microevolutionary arms race, where L. fasciculata developed thicker shells for protection while predators simultaneously honed their ability to breach these defenses despite the increasing strength of their prey’s armor.
“This vital evolutionary finding indicates, for the first time, the significant role that predation played in the growth of early animal ecosystems and highlights the rapid pace at which such physical adaptations emerged during the Cambrian Explosion,” Bicknell stated.
This research received partial funding from the University of New England, the American Museum of Natural History, and the Australian Research Council (grant #s DP200102005 and DE190101423).
