  Globally disruptive events include asteroid/comet impacts, large igneous
provinces and glaciations, all of which have been considered as contributors to
mass extinctions. Understanding the overall relationship between the timings of
the largest extinctions and their potential proximal causes remains one of
science's great unsolved mysteries. Cycles of about 60 million years in both
fossil diversity and environmental data suggest external drivers such as the
passage of the Solar System through the galactic plane. While cyclic phenomena
are recognised statistically, a lack of coherent mechanisms and a failure to
link key events has hampered wider acceptance of multi-million year periodicity
and its relevance to earth science and evolution. The generation of a robust
predictive model of timings, with a clear plausible primary mechanism, would
signal a paradigm shift. Here, we present a model of the timings of globally
disruptive events and a possible explanation of their ultimate cause. The
proposed model is a symmetrical pattern of 63 million-year sequences around a
central value, interpreted as the occurrence of events along, and parallel to,
the galactic midplane. The symmetry is consistent with multiple dark matter
disks, aligned parallel to the midplane. One implication of the precise pattern
of timings and the underlying physical model is the ability to predict future
events, such as a major extinction in one to two million years.
