How would you evolutionists explain this?

Compmage is pointing out a contradiction in your position. You're demanding an ultimate cause for the scientific perspective, but not of the religious perspective.For example, if you insist of science that the Big Bang have an origin, then you must equally insist of religion that the Big Being have an origin. And if your answer for the Big Being is that he has existed forever, then why do you reject the same answer for the universe?JEP: Let’s see if I can add to this thread. Something started this thing we call the big bang. Things in motion have to be put into motion by something; and we can tell simply by observing our universe around us, that it is expanding rapidly. So, what caused this?Something did and it could not have come from our universe because our universe did not exist before the big bang.Our three spatial dimensions of height, width and depth and our fourth dimension called time were created in the big bang. Before the bang, there were no spatial dimensions in our universe in which to put anything that it could exist. There also was no time in which anything could exist. The basel element of the very word called existence requires a space-time constituent in order to be sensical.
So, we can determine that something ‘caused’ this universe.If God exists then doesn’t He also require a cause? No. And for the very same reasons that the big bang DOES require a cause. If God created the universe and before this creation there was no time, then we can quickly determine that there was no such thing as the words before and after because they are dependent on time. If there is no such thing as a ‘before God,’ then it becomes a moot question to ask what created him because nothing could have pre-existed Him in order to ‘cause’ Him. God just always was. Interestingly enough, this is what the Bible teaches and I find it fascinating that it also teaches that the dimension called eternity that God lives in is a time-less phenomenon.Please read the writings of philosopher Auther Custance for more on this.

Because it can be logically deduced:P1 If God 'caused' the big bang He would have had to pre-exist the big bang.P2 Time was created in the big bang and therefore did not pre-exist the big bang.Conc: Therefore, God pre-existed time.Syllogism II:P1 God pre-existed time.P2 The term 'before' is a nonsensical term when no time is present.Conc. Therefore, there is no such thing as 'before God.'Can you see that if God does exist and there is no 'before God,' then it is quite logical to state that He always was?

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Sure, I can see that, but why, logically, add another whole layer of causation into the start of our universe just because you'ld prefer some sort of afterlife? If time was created in the Big Bang, why not leave it at that? /quoteJEP: That is a very valid question. But could I get you to see that, to me, it’s not a matter of any preference I havebut it’s more of a personal belief that this is the way things are in reality?Of course, I could just be dead wrong and there is no God at all. I certainly don’t get it right all the time. But I think there is, and if there is, then inquiring minds want to understand the universe He created.And finally, of course, part of the syllogism post was simply to overcome the old argument that if everything has a cause then God must have a cause. Taint necessarily that way.

Hmmm....I'm doing great with the quote deal as all can see.