[meteorite-list] Cyclic mass extinction?

[Edward R. Hodges]

I happened to catch the last few minutes of a show on PBS about extinction. One of the scientist had compiled data on thousands of extinct species and graphed the times of their extinction. In the timeline he created there seemed to be above normal rates of mass extinction every 26 million years. Another scientist is working on a theory that the sun has a companion star, "Nemesis" that perturbs the orbit of comets in the Oort cloud which impact the Earth roughly every 26 million years. Who can shed some light on this topic? Wouldn't there be clear evidence of meteoritic dust fallout in clay deposits in strata spanning every 26my? Interesting, very interesting. Didn't catch the name of the show, or the names of the scientists.- Edward   Edward R. Hodges www.meteoriteonline.com IMCA#4173