Long-Term Cycles in the History of Life: Periodic Biodiversity in the Paleobiology Database

Adrian L Melott

doi:10.1371/journal.pone.0004044

Abstract

Time series analysis of fossil biodiversity of marine invertebrates in the Paleobiology Database (PBDB) shows a significant periodicity at approximately 63 My, in agreement with previous analyses based on the Sepkoski database. I discuss how this result did not appear in a previous analysis of the PBDB. The existence of the 63 My periodicity, despite very different treatment of systematic error in both PBDB and Sepkoski databases strongly argues for consideration of its reality in the fossil record. Cross-spectral analysis of the two datasets finds that a 62 My periodicity coincides in phase by 1.6 My, equivalent to better than the errors in either measurement. Consequently, the two data sets not only contain the same strong periodicity, but its peaks and valleys closely correspond in time. Two other spectral peaks appear in the PBDB analysis, but appear to be artifacts associated with detrending and with the increased interval length. Sampling-standardization procedures implemented by the PBDB collaboration suggest that the signal is not an artifact of sampling bias. Further work should focus on finding the cause of the 62 My periodicity.

Highlights

The first high significance detection of long-term periodicity in the fossil record is fairly recent [1], based on marine fossil biodiversity over,500 My
No particular causal mechanism was proposed, but the result was initially published based on its relatively high statistical significance (p = 0.01) and potentially strong implications. These studies were all based on a large compendium [4] which was not controlled for systematic errors such as sampling rate
I have shown that a periodicity at 6263 My with essentially identical period and phase which was uncovered [1] in the Sepkoski dataset [4] appears in the Paleobiology Database data [7]

Summary

Introduction

The first high significance detection of long-term periodicity in the fossil record is fairly recent [1], based on marine fossil biodiversity over ,500 My. No particular causal mechanism was proposed, but the result was initially published based on its relatively high statistical significance (p = 0.01) and potentially strong implications. These studies were all based on a large compendium [4] which was not controlled for systematic errors such as sampling rate. Such systematic errors may compromise quantitative study [5,6]. A statistical study of this dataset concluded with the statement that evidence for autocorrelation did not exist, which result is inconsistent with periodicity [8]. I have found a specific periodic signal consistent with reports based on older data [1,2,3]

Methods

Results

Conclusion