Periodicity of Extinctions in the Geologic Past (Raup & Sepkoski)
First published: 1984
Brief summary
Foundational statistical study finding a significant ~26 million year periodicity across 12 major marine extinction events over the past 250 million years, launching decades of follow-up research.
Article
Periodicity of Extinctions in the Geologic Past (Raup & Sepkoski) is a peer-reviewed journal article published by Proceedings of the National Academy of Sciences in 1984. It is a foundational statistical study that finds a significant ~26 million year periodicity across 12 major marine extinction events over the past 250 million years, launching decades of follow-up research.
The analysis focuses on 26 Myr, statistically significant at P<0.01. The data source is fossil family extinction intensity record for marine vertebrates, invertebrates and protozoans. This gives the cycle claim a specific numerical and evidential setting rather than presenting periodicity only as a visual impression.
The article reports the following result: The 12 events show a statistically significant periodicity (P less than 0.01) with a mean interval between events of 26 million years; two of the events coincide with extinctions previously linked to meteorite impacts. The interpretation is strongest when it survives dating uncertainty, preservation bias, alternative event selections and correction for multiple statistical tests.
For cycles researchers, the article brings together mass extinction periodicity, 26-million-year cycle, marine extinctions, fossil record. It is relevant to debates over whether recurring patterns in the geological record reflect astronomical forcing, internal Earth processes, preservation bias or dating uncertainty.
Because it is a peer-reviewed journal article, the article is a strong starting point for discussion in the Geology & Paleontology forum, although its conclusions should still be compared with later replications and updated datasets.
Source details and credits
- Source / publisher: Proceedings of the National Academy of Sciences
- Source type: Peer-reviewed journal article (foundational, pre-2000)
- URL type: WWW
- Credits: Proceedings of the National Academy of Sciences
- URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC344925/