JAbout 500 million years ago, life on Earth evolved from simple single-celled organisms to complex multicellular life forms. The Cambrian Explosion produced many strange and wonderful new inhabitants, such as the five-eyed Opabinia and the spiny slug Vivaxia. Pulses of oxygen in the atmosphere and ocean are thought to have contributed to the diversification, but it is still unclear what causes the oxygen fluctuations. Now the study suggests that changes in Earth's orbit could be behind these evolutionary impulses.
The researchers used a climate and biogeochemical model and studied how periodic shifts in Earth's orbit affect the amount of solar energy reaching Earth. They found that changes in solar energy every two to three million years keep pace with the rise and fall of observed oxygen levels.
Sign up for Letters on Geophysical ResearchThe researchers hypothesize that changes in solar energy caused climate changes that altered the extent to which land surfaces were weathered—especially at high latitudes—with periods of rapid weathering releasing a surge of nutrients into the oceans that stimulated photosynthesis and increased oxygen levels, fueling rapid evolutionary changes.
Similar orbital changes occurred at other times, but only the Cambrian period had all the ingredients for this exceptional evolutionary burst.
