This thread is boring. What "caused' the beggining of the Universe is not even a question, because causality can only explain things after there is matter and energy - because causality is rule-based and only works to explain results of physical interactions. Without matter and energy there is nothing to have a cause. For all practical purposes, the first cause was the appearance of matter and energy, and what originated it cannot be explained by causality. Without matter and energy there are no rules of physcal interaction, and without this there is no cause and effect.
Now, why is it that people assume that, because the Universe exists in an ordained fashion and is complex, that an intelligence must have created it? Epistemologically speaking, the principle of entropy states that the Universe must exist somehow. Maybe there are infinite universes that are simpler than a game of checkers, and maybe there are universes that don't require logic at all to operate. How would creationists and intelligent designers explain the existence of a universe that has no coherence at all - meaning that it's organization requires 0 intelligence?
Personally, I believe that the explanation of what gave origin to the Universe is a Human problem. It is based on the fact that our minds were created to operate with inductive and deductive logic, which resulted from natural selection for us to understand our rule-based Universe. So asking what "caused" the Universe doesen't make sense, and it is not lack of intelligence but rather the specific design of our minds that makes us being trapped into assuming that, because cause and effect is so good at explaining the workings of our Universe, that it can explain something that probably does not even require logic.
SUCKMYMUSCLE