Is infinity a reality in your universe? Once one accepts infinity as a reality, he can introduce both definite beginnings, or no beginnings at all, into reasonable discussion. Even a simpleton like me knows that.
If you wish to reject infinity as a reality, then please bear in mind that it is YOU who will wear the label of "anti-rational" in that regard and not creationists.
But you are not altogether anti-rational, or I could not even communicate with you. By and large I consider you and all evolutionists to be more than decent examples of intelligent design, but I don't think my opinion of you has much to do with your concerns.
As long as "infinity" remains an abstract rather than concrete (i.e., with evidence) concept, it is not rational to invoke it scientific research.