In my opinion, empirical evidence on historical events that lead to severe reductions in human population size is very important for those studying global catastrophic risks and potential extinction risks. A new study in Science provides novel evidence that such an event occurred 930,000 years ago. To give a few quotes:

• "Results showed that human ancestors went through a severe population bottleneck with about 1280 breeding individuals between around 930,000 and 813,000 years ago. The bottleneck lasted for about 117,000 years and brought human ancestors close to extinction. This bottleneck is congruent with a substantial chronological gap in the available African and Eurasian fossil record."
• "Results showed that our ancestors experienced a severe population bottleneck between about 930 and 813 kyr BP, most likely because of climatic changes. The average number of breeding individuals was only about 1280 during the bottleneck period. Our findings indicate that the severe bottleneck brought the ancestral human population close to extinction and completely reshaped present-day human genetic diversity."
• "The bottleneck was estimated to persist for 117 kyr, from 930 ± 23.52 (SEM) (range, 854 to 1042) to 813 ± 11.02 (SEM) (range, 772 to 864) kyr BP. The average effective population size (i.e., the number of breeding individuals) (26) during the bottleneck period was determined to be 1280 ± 131 (SEM) (range, 770 to 2030), which was only 1.3% of its ancestral size (98,130 ± 8720; range, 58,600 to 135,000). To evaluate the impact of the bottleneck on current human genetic diversity, we analyzed the expected pairwise nucleotide diversity. Results showed that 65.85% of current human genetic diversity was lost because of the bottleneck."

The NYTimes has a nice article covering the study. The study uses a novel method to uncover these results (FitCoal), and as the article suggests, there is debate within the field over these results. I suspect this study will draw new studies to assess this hypothesis. In any case, I figure that these results are quite interesting/important for those interested in global catastrophic risks to be aware of.