Might dark matter play a role in extinctions…? I don’t know but it sounds plausible at least.
Although statistical evidence is not overwhelming, possible support for an approximately 35×10^6 yr periodicity in the crater record on Earth could indicate a nonrandom underlying enhancement of meteorite impacts at regular intervals. A proposed explanation in terms of tidal effects on Oort cloud comet perturbations as the Solar System passes through the galactic midplane is hampered by lack of an underlying cause for sufficiently enhanced gravitational effects over a sufficiently short time interval and by the time frame between such possible enhancements. We show that a smooth dark disk in the galactic midplane would address both these issues and create a periodic enhancement of the sort that has potentially been observed… (PDF - Lisa Randall and Matthew Reece)
Image by Alan Stonebraker