A study led by researchers at the American Museum of Natural History has uncovered the oldest known example in the fossil record of an evolutionary arms race. The study, published in the journal Current Biology, details predator-prey interactions that occurred 517 million years ago in the ocean covering what is now South Australia. The interactions involved a small, shelled animal distantly related to brachiopods and an unknown marine animal capable of piercing its shell. This discovery provides the first demonstrable record of an evolutionary arms race in the Cambrian period.
According to Russell Bicknell, a postdoctoral researcher at the Museum’s Division of Paleontology and lead author of the study, predator-prey interactions are often considered a major driver of the Cambrian explosion, which saw a rapid increase in diversity and abundance of biomineralizing organisms. However, there has been a lack of empirical evidence showing that prey directly responded to predation and vice versa. The new findings shed light on the role of predator-prey interactions in driving evolutionary changes during the Cambrian period.
An evolutionary arms race is a process in which predators and prey continuously adapt and evolve in response to each other. This dynamic is likened to an arms race because improvements in one species lead to counter adaptations in the other species. The researchers studied a large sample of fossilized shells belonging to an early Cambrian species called Lapworthella fasciculata from South Australia. These shells, ranging in size from slightly larger than a grain of sand to just smaller than an apple seed, showed evidence of being pierced by a hole-punching predator, likely a soft-bodied mollusk or worm.
By analyzing these shells in relation to their geologic ages, the researchers found a correlation between an increase in shell wall thickness and the number of perforated shells in a short amount of time. This suggests that a microevolutionary arms race was taking place, with L. fasciculata fortifying its shell against predation and the predator investing in the ability to puncture its prey despite the prey’s armor becoming thicker. The study provides critical evidence of the role of predation in driving early animal ecosystems and highlights the rapid speed at which such phenotypic modifications arose during the Cambrian explosion event.
The research was funded in part by the University of New England, the American Museum of Natural History, and the Australian Research Council. The findings of the study not only contribute to our understanding of predator-prey interactions during the Cambrian period but also provide important insights into the role of evolutionary arms races in driving ecological dynamics and shaping the diversity of early animal ecosystems. This study represents a significant step towards unraveling the mysteries of ancient predator-prey relationships and their impact on the evolution of life on Earth.
