I remember Stephyen Jay Gould wrote an essay caleed the "cosmic dance of Shiva" where he talked about how the fossil record suggests that mass extinction events

I remember Stephyen Jay Gould wrote an essay caleed the "cosmic dance of Shiva" where he talked about how the fossil record suggests that mass extinction events at regular intervals of 20 something million years. He wrote that since it would be difficult to find a terrestrial explanation for an extinction event at regular intervals, so it made sense to look at factors from outer space. This could be the sort of missling link in Gould's theory. I can't find a non-paywalled version of Goud's article but here is another one talking about mass extinctions at regular intervals http://www.theatlantic.com/science/archive/2015/11/the-next-mass-extinction/413884/ http://www.theatlantic.com/science/archive/2015/11/the-next-...