The two books are complementary. Certainly I'm not going to forward an explanation of why a mamoth would die and freeze in the ice, rapidly enough to preserve it as edible, even though the animal had undigested grass in it's stomach. But it's certain the cause was neither Venus nor Mars bumping into the Earth's magnetosphere as proposed and altering the axis of rotation. And definitely not within human memory. Nope. Didn't happen. Sir Isaac Newton forbids it.