In this "NOVA Minute", geologist Sam Bowring from MIT offers his thoughts on mass extinctions.

Produced by David Levin. Original interview by Julia Cort. NOVA is produced by WGBH in Boston. Funding for NOVA is provided by ExxonMobil, David H. Koch, the Howard Hughes Medical Institute, the Corporation for Public Broadcasting, and public television viewers.

Learn more at pbs.org/nova/sciencenow