Neil deGrasse Tyson on paleontology: what the evidence says · JRE #919
SUBJECT: PALEONTOLOGY
Not a true/false call. Every claim is logged with its sources; read the exhibits below.
And every 20,000 years, they found a little blip a little dip in The fossil record where we lost some species and people were wondering why could there have been some flux of comets raining down?
What the evidence says 01 / RECORD
Tyson describes a periodic dip in the fossil record that prompted scientists to hypothesize a companion star to the sun (later dubbed Nemesis) triggering comet showers, but states the interval as roughly every 20,000 years. The actual finding, published by Raup and Sepkoski in 1984, identified a statistically significant periodicity with a mean interval of approximately 26 million years between major extinction events over the past 250 million years. This periodicity, not a 20,000-year cycle, is what motivated the Nemesis hypothesis. Subsequent observational surveys, including NASA's WISE infrared sky survey, found no evidence of a companion star at the distances required, further arguing against Nemesis-based extinction theories (which were already considered largely ruled out on other grounds before WISE). Tyson's description of the underlying mechanism and scientific history is accurate, but the stated interval is off by roughly three orders of magnitude (20,000 years versus roughly 26 million years).