The problem I see with the doomsday argument is that in the example with the urns, both urns have reached their final value, while the human population is still growing, our urns are still being filled. <br><br>So if we say that to fill those urns we need (hundreds of) thousands of years to reach the final number of balls and assume both urns are being filled at the same rate, if we then at year 5000 take a random sampling from one of the urns, they will actually both contain the same number of balls and we'd still have a 50/50 probability.