If you choose the first answer "Natural evolution", please describe how "random mutations" increase genetic information as opposed to actually destroying it.
I believe the answer to this is philosophical.
Why does anything have to exist at all?
Because, I believe, everything must have an opposite. Including "nothingness".
In order for there to be "nothing" there also has to be "something".
Likewise, in order for there to be darkness, there has to be light.
In order for the opposite of nothingness to exist, there has to be a creating intelligence behind it. Which is why intelligent life evolves in the universe.
the big bang, which came from where?
This intelligence, if it reaches the maximum intelligence possible, will be able to create other universes (big bangs) in which life will evolve in order for the perpetual creation of universes to be sustained.
In other words, DNA comes from a process originating from nothing at all.
Pardon a beginners intrusion. I think that nothingness and anythingness only exist for humans, because we have a brain capable of juggling things beyond the basic drives to eat and reproduce, both of which exist in the 'brain' of the cockroach, and the lobster. Heck, in all living things flora or fauna. The incentive to exist and move forward has nothing to do with a brain. Those with a brain are partially cursed. To a rat, emptiness and fullness are rated by the gut, and the sinew in the tooth. If he then gets laid, and if he could or wanted to say anything at all, wouldn't it be 'life is sweet'?
Lightness and darkness don't need explaining to most animals. It's a given, we've adapted, I have more success eating at night than I do in the daylight, or whatever my (species) chosen strategy.
I say that nothingness exists except for the dead (who couldn't care), and for (living) humans as an abstraction, simply because we've got that 'capable of juggling things brain'. When the juggling stops, we're animals again, but worse, we're the cat kicked out of the house to become feral again or die trying. Or the flushed turtle.
I ate well tonight, I'm (hopefully) gonna get laid, and when I'm satiated, emptied, and subsequently bored I'll see if I still have any weird phenomenological text books that I once enjoyed trying to understand, and the existential stuff that I tended toward because it suited my adolescent demeanor but still didn't understand. I outgrew itl. I was a sham. My endeavors were shallow and hopeless. I'm going to concentrate on getting laid
I'm glad to see that some people still think about things, but I don't envy you.