研究揭示寒武纪大爆发的“幕后推手”

Core Insights - The Cambrian explosion represents a critical milestone in the evolutionary history of life on Earth, characterized by a rapid emergence of nearly all existing animal phyla [1] - The driving mechanisms behind the pulsed oxygenation during this period remain unclear, despite evidence linking it to periodic atmospheric and shallow marine oxygenation [1] Group 1: Research Findings - A research team from the Nanjing Institute of Geology and Palaeontology has revealed that long-term orbital changes may be the driving force behind the pulsed oxygenation process during the Cambrian period [2] - Previous studies indicated that marine animal diversity exhibited periodic changes over a timescale of approximately 2 to 3 million years, correlating with fluctuations in seawater carbon and sulfur isotopes [2] - The research suggests that global organic carbon and pyrite burial undergo periodic changes, affecting atmospheric and shallow marine oxygen levels, which in turn influence early marine animal evolution [2] Group 2: Methodology and Results - The study conducted spectral analysis on published carbon-sulfur isotope records from the early Cambrian, identifying long-period changes of 1.2 million, 2.6 million, and 4.5 million years that align with long-period orbital changes [3] - Numerical simulations using a deep-time Earth system box model (SCION) demonstrated that climate changes driven by orbital factors can replicate the synchronous periodic variations in seawater carbon-sulfur isotopes, supporting the hypothesis [3] - Sensitivity experiments indicated that low sulfate concentrations in the ocean may amplify the response of the carbon-sulfur-oxygen biogeochemical cycle to nutrient inputs driven by orbital changes, highlighting a critical shortcoming in the stability of the Cambrian Earth system [3]