Oxygen and carnivores may explain Cambrian explosion

Science News : Between 540 million and 500 million years ago, a massive proliferation of modern life forms occurred, known as the Cambrian explosion . The cause for the sudden increase is unknown, though many theories have been put forth. Erik Sperling of Harvard University and his colleagues believe they have tied two theories together into a more complete explanation. The geologic record indicates a significant increase in oxygen levels during the same time period, and the appearance of carnivorous species may have driven an arms race of evolutionary responses. Sperling’s group examined data on nearly 1000 species of worms from 68 locations on the sea floor and found that the number of carnivorous species was lowest in the areas with the lowest oxygen levels. They believe that the increase in oxygen is what allowed the development of successful carnivores—the higher concentrations of the gas accommodated the higher energy costs of pursuing and digesting prey.