Imagine the entire world is covered with a stormy ocean. Deep in this vast ocean, long before the continents emerged, there was a single tortoise who only surfaces once every hundred years for air. Along with the tortoise, there was one other object in this ocean: a wooden yoke, like you'd put on a yak. The probability of the tortoise surfacing so that it puts its neck through the yoke is greater than the probability of our attaining a human rebirth in our next lifetime.