But the data indicates that the extinctions occur every 27 million years, as regular as clockwork. “Fossil data, which motivated the idea of Nemesis, now militate against it,” say Melott and Bambuch.
That means something else must be responsible. It’s not easy to imagine a process in our chaotic interstellar environment that could have such a regular heart beat; perhaps the answer is closer to home.
Over the last 500 million years or so, life on Earth has been threatened on many occasions; the fossil record is littered with extinction events. What’s curious about these events is that they seem to occur with alarming regularity.
The periodicity is a matter of some controversy among paleobiologists but there is a growing consensus that something of enormous destructive power happens every 26 or 27 million years. The question is what?
“An amazing performance by jazz artist Anita O’Day, 1957. This clip is featured off of ‘Jazz on a Summer’s Day.’”

