Please define this. All I can find on it is a wiki article, and I don't take those as being accurate.
And what do you mean by "believe?" Most scientists accept a theory when the evidence becomes overwhelming, but belief is another thing entirely.
Heinlein probably said it best:
Belief gets in the way of learning.Robert A. Heinlein, Time Enough for Love, 1973
So, Coyoteman, do you accept the theory of a past global genus extinction event?