Dan'S_mind’s Reviews > How to Read Darwin > Status Update

The number of mass extinctions that have occured during the history of life is uncertain. Estimates range from as few as 2 to as lany as 13.Darwin's basic explanation -flanctuations on the sedimentary record- may explain some of the controversial appatentmass extinctions,even if it does jot explain all of them. The importance of biological competition in causing extinction also remains unknown, 'cause its so hard to