Sepkoski J J
Department of the Geophysical Sciences, University of Chicago, Illinois 60637, USA.
J Geol Soc London. 1989;146:7-19. doi: 10.1144/gsjgs.146.1.0007.
The hypothesis that extinction events have recurred periodically over the last quarter billion years is greatly strengthened by new data on the stratigraphic ranges of marine animal genera. In the interval from the Permian to Recent, these data encompass some 13,000 generic extinctions, providing a more sensitive indicator of species-level extinctions than previously used familial data. Extinction time series computed from the generic data display nine strong peaks that are nearly uniformly spaced at 26 Ma intervals over the last 270 Ma. Most of these peaks correspond to extinction events recognized in more detailed, if limited, biostratigraphic studies. These new data weaken or negate most arguments against periodicity, which have involved criticisms of the taxonomic data base, sampling intervals, chronometric time scales, and statistical methods used in previous analyses. The criticisms are reviewed in some detail and various new calculations and simulations, including one assessing the effects of paraphyletic taxa, are presented. Although the new data strengthen the case for periodicity, they offer little new insight into the deriving mechanism behind the pattern. However, they do suggest that many of the periodic events may not have been catastrophic, occurring instead over several stratigraphic stages or substages.
过去25亿年中灭绝事件周期性重现的假说，因海洋动物属在地层中的分布范围的新数据而得到极大加强。从二叠纪到现代的这段时间里，这些数据涵盖了约13000次属级灭绝事件，与之前使用的科级数据相比，它能更灵敏地指示物种层面的灭绝情况。根据属级数据计算得出的灭绝时间序列显示出九个强烈的峰值，在过去2.7亿年中，这些峰值几乎以2600万年的间隔均匀分布。这些峰值中的大多数对应于在更详细但有限的生物地层学研究中识别出的灭绝事件。这些新数据削弱或否定了大多数反对周期性的观点，这些观点涉及对分类数据库、采样间隔、计时时间尺度以及先前分析中使用的统计方法的批评。本文对这些批评进行了较为详细的审视，并给出了各种新的计算和模拟结果，其中包括一项评估并系类群影响的模拟。尽管新数据强化了周期性的观点，但它们对于该模式背后的推导机制并没有提供多少新的见解。然而，它们确实表明，许多周期性事件可能并非灾难性的，而是在几个地层阶段或亚阶段中发生的。
