On 2013-01-10, Mark IV wrote:
If flying wings are "intrinsically unstable", then why
did millions of years of evolution not produce birds
with vertical stabilizers.

I'd wager that birds are intrinsically unstable. Don't forget
birds have a very good active stabilization system (a brain
directly connected by nerves to the wings) plus highly variable
geometry, angle of incidence and dihedral. Wheras our machines
have poxy little ailerons.