Was the ‘dawn of carnivores’ the cause of the broad explosion of animal species and body plans/structures during the Cambrian period 540 million years ago? That’s what new research from the Scripps Institution of Oceanography at UC San Diego is suggesting — that the emergence of carnivores (as well as the atmospheric conditions favorable to them) is what spurred the incredible radiation of animal life that occurred at this time.
For the new work, the researchers analyzed how “low oxygen zones in modern oceans limit the abundance and types of carnivores to help lead them to the cause of the ‘Cambrian radiation,’ a historic proliferation of animals 500-540 million years ago that resulted in the animal diversity seen today.”
While the exact cause(s) of the influx of oxygen is still a matter a scientific controversy, the Cambrian radiation that followed it is “the most significant evolutionary event in the history of animals.”
“During the Cambrian period essentially every major animal body plan — from arthropods to mollusks to chordates, the phylum to which humans belong — appeared in the fossil record,” stated lead researcher Erik Sperling of Harvard University. “The authors linked this proliferation of life to the evolution of carnivorous feeding modes, which require higher oxygen concentrations. Once oxygen increased, animals started consuming other animals, stimulating the Cambrian radiation through an escalatory predator-prey ‘arms race.'”
In recent years oxygen levels have been decreasing in much of the world’s oceans as a result of human activity. “While the Cambrian radiation exploded with new species and diversification, the researchers believe this study suggests the reverse may ensue as oxygen declines and oxygen minimum zones expand.”
“This paper uses modern oxygen gradients and their effects on marine worms to understand past evolutionary events” stated Lisa Levin, a professor of biological oceanography at Scripps. “However, the study of oxygen’s role in the past is also going to help us understand the effects of and manage for changes in ocean oxygen in the future.”
The new research was just published July 29th in the online edition of the Proceedings of the National Academy of Sciences.