We Never Know
No Slack
Science universally recognizes the "cause and effect" law as a settled science. This law states that every effect must have a cause, in other words nothing can happen unless something causes it to happen. If we apply this law to the Big Bang Theory and the Theory of Evolution, it exposes them as being fundamentally flawed theories. As both theories are lacking a cause, or foundation.
Logic tells us that nothing came form nothing, and nothing happens unless something causes it to happen. Life is tooo complexed to suggest it came out of nothing, if we look at a Picasso painting it bares witness of an artist. How much more complexed is life. It takes a lot more faith to believe that life spontaneously evolved without a designer.
I think I read once that things that exist require a cause. However without a beginning, that has always existed, does not require a cause.
With that said... if the universe always existed, it has no cause. If it has a beginning, then it has a cause.