Firstly, and I'm not assuming that you intend a creator god to be the preferable explanation (though of course many do), the same question can be applied to that god. If one always existed, he/she just sat there for an eternity before acting. Why?
Secondly, models of an open, non-oscillating universe generally imply that time as we know it did not exist before (or as one apologist put it, "ontologically prior to") the Big Bang. As one part of Einstein's theoretical combination "spacetime", it was wrapped up with everything else in the singularity (speck) and its apparent forward flow began when the expansion did. Going by this type of model, it wasn't possible for anything to happen "before" the Big Bang. Stephen Hawking likened the question to asking what's north of the North Pole.
Thirdly, it's possible that there are systems of time and space outside the universe we know, and our universe was set off by one of these. There are various models of a multiverse, collectively infinite in both time and matter, where universes regularly beget other universes. There are also slightly simpler models of a single external mother universe or "metaverse" which spawns the others. These are speculative, of course, but at least the extra entities being posited are objects we know exist in at least one case, i.e. universes.
Finally, new evidence is emerging which may challenge the singularity's perceived lack of a beginning. It may be best to wait and see.
I think what you're saying is that because God created life billions of years ago, and we can't, God is better than us at molecular biology.
If we last another 6 billion years we probably will succeed in creating new life. We've made tremendous progress in just the 50-ish years since the Miller-Urey experiments, which created 22 kinds of amino acids from primitive swamp gas and lightning. We haven't succeeded in causing life to emerge yet, but we can produce all kinds of precursors. If we have 120 million times as long to try, I think we'll get there.
As for the initial life that evolved into us, it needn't have been created at all. The very fact that we're finding it so difficult to do deliberately suggests that it happens more easily as a natural process. The Earth is vast, the chemical ingredients it provides are diverse and plentiful and they had billions of years to mix. The sheer number of possible combinations is staggeringly large. The odds against one of those combinations resulting in life? Not so large.
According to the Book of Genesis, the "morphing" process between species didn't happen. According to archaeological and biological evidence, however, humans got to be as they are now very, very, VERY slowly.
No ancient ape actually morphed. Apes just had a lot of children, and some of those children were different in tiny ways. Some were smarter, some were stronger, some had less hair. If the changes helped the children to survive and have kids of their own, the changes stuck by way of plain old heredity. If changes didn't help, they died out. That's what we call natural selection.
This went on for millions of years, so the changes stacked up over time. Notice how a playing card is practically flat, but a deck of cards has thickness? That's how unnoticeable changes can eventually add up to big changes. Our deck had a lot of stacking time.
As the population grew, groups of apes separated and began to pass on different changes. One group survived through sheer strength, and developed into gorillas. Another group found that being smaller helped them escape things that wanted to eat them, and ended up as chimpanzees. One group prospered because of its greater intelligence, so it kept on getting smarter. That group was our ancestors.
So you see, we didn't develop from the apes we see in jungles and zoos today. We and they are all descended from common ancestors, entirely different apes which aren't around anymore. Modern apes aren't our ancestors, they're our distant cousins. That's why we share a lot of our DNA with them.
We look back at this process through all the fossils we've found of the different forms our ancestors took, and we have to ask, "When did these apes become humans?" All we really did was pick a point about two million years ago when they were humanlike enough, and declare, "There. We started there. Everything before that was just apes." All species after that point were named Homo, because that's the Latin for "man". The first was Homo habilis, and we are the last one so far, Homo sapiens.
The reality is that we didn't morph from apes, we are highly advanced apes ourselves. It's like how a square is also a rectangle, but it has unique qualities.
You might think it's an insult to call all humans apes, but it's not. If we're apes, then everything we are is part of what an ape can be. Apes can write poetry, build machines, give to charity. Apes can look up at the sky and wonder. Apes can be romantic. Apes can be human. I'm proud to be an ape.
On the other hand, if things happened exactly as the Book of Genesis says they did, we've got nothing to do with apes and all the accepted evidence is wrong. If you want to look at it that way, fine, but you're rejecting a lot of evidence. Go check it out.
If you're going to argue that abiogenesis is not science, it might help to define science first.
Science is the formulation of natural explanations for observable phenomena in the universe. Abiogenesis (the emergence of life from non-life), while not yet observed itself, is a natural explanation for the observable phenomenon of life. It is therefore a scientific hypothesis, and yes, it is science. What it is not (yet) is a theory.
Though some natural selection may have occurred in the process, abiogenesis should not be classified as chemical evolution. It may have been a rapid, non-cyclical process instead. We freely admit that we have no clue how it happened.
At least until we do observe a second abiogenesis in a lab or in nature (positing that the event which produced us was the first), not only do we stick to speculation as to how it happened, but we refrain from stating 100% certainty that it did happen. If evidence of intelligent design were to emerge (say, actual physical impressions of fingerprints in our DNA) we would soon abandon the hypothesis that we are the products of abiogenesis. We would then try to determine whether the designer was a god, an alien or an extinct Earth creature, and in all three cases start to hypothesise about the abiogenesis and evolution of that being, if any.
This is the difference between a scientific hypothesis and a faith position. We assume a scientific hypothesis for practical purposes as the best current explanation until a better one comes along, at which point we chop and change. We're not precious about it at all, at least until it accumulates enough evidence to be declared a theory. A man with a faith position defends it to the end, because he usually expects no contradictory (or even supporting) evidence to present itself.
Another difference is that a hypothesis must be falsifiable, which means there must be some hypothetical event which demonstrates it is false. Our abiogenesis is falsifiable because we might find firm evidence of a creator, like a signature or a work log billions of years old. By comparison, what would falsify the intelligent creation of life? Nothing. Even if we achieved abiogenesis in a lab, it might be the case that although abiogenesis is possible, we were still designed.
On the basis of this last point, I submit to you the idea that intelligent creation of life is a faith position where abiogenesis is not. There may be additional ways to establish this comparison, but I'll leave it at that for now.
I've seen the genetic code argument before, you know. The idea is that all codes are intelligently designed, so the existence of one in DNA proves a designer. That's an argument from ignorance because there is no evidence that a code is impossible without a designer. Further, if you present this argument, I can provide examples of naturally occurring codes which have nothing to do with life, like the means by which mineral crystals can transmit their structure to non-crystallised material.
There's another side to the genetic code argument which states that it's impossible for new information to appear naturally. We've been over that here.
What we have here is a laundry list of creationist talking points. Thanks for rounding them up for me.
There are more than a few bits and pieces of transitional fossils. Here is a list of hundreds of excellent examples of transitional species for which adequate-to-plentiful fossil evidence has been found. If you want to research a couple in detail, I recommend Ambulocetus (which means "walking whale") and the famous Tiktaalik. Suit yourself though, you're spoilt for choice.
The Cambrian period was fifty million years long. The "explosion" itself happened in a relatively short period at the beginning, but "relatively short" in this context can still stretch over several million years. That's hardly instantaneous, and it certainly isn't beyond the capabilities of ordinary evolutionary diversification. The going theory is that animals in general emerged at about that time, or even during the "explosion"; such completely new life forms would have had a lot of licence to spread and change.
The odds of any specific species emerging are astronomical indeed, but given that an almost unlimited number of hypothetical species could have appeared in their place, the odds of something appearing probably approach certainty. Think of the lottery; every entrant has a one-in-umpteen-million chance of winning, but how often does someone take the jackpot anyway? Never more than a few weeks go by before it happens. Why? Because everybody's got a ticket. (As for the odds on the diversity of the Cambrian explosion, just what are the astronomical odds you're on about?)
Use your browser to search this article for the word "observed" to find some recent examples of new species emerging before our eyes. It's true that these examples generally have some important new feature or dimensions rather than being an entirely new type of animal, but unfortunately the sorts of changes I think you'd like to see take thousands of times too long to observe in a human lifespan. Sorry, but it's like asking to watch the erosion of the Grand Canyon. Even if you'd been there when the water was, you might not have noticed a thing even if you stared at it for years. You'd need the equivalent of a time-lapse film, and that's what the geological (for fossils, the paleontological) record provides.
Recorded history is seven thousand years long at the most (writing was only invented about 5500 years ago, so before that it's all symbols and drawings). Current understanding of our pre-human ancestry indicates a new species of primate every one to five hundred thousand years. Recorded history therefore stretches back far enough to allow for 7%, at most, of the change necessary to declare a new species. Given the diversity of human bodies, the sheer deviation from various averages, 7% isn't enough to pick out the actual evolution from plain old human differences.
Again, sorry, but we're just not around long enough to spot this stuff happening around us. Nevertheless, every piece of evidence we have tells us that it does.
This is the Cosmological Argument. I've answered it most thoroughly here, but also to some extent here, here and in a comment here. Jake and Carl Sagan have their own answers here. Look through them and choose your own solutions from that lot to either accept or argue.
I'll just add that simply because the Big Bang seems to imply something which seems nonsensical to you doesn't necessarily mean that it is actually nonsensical, let alone impossible, or that it even implies what you think it does.
Nothing yet adequately addresses the reality of a rational universe, Jack, not even gods.
You're a little too focused on the multiple-universe hypothesis. It's not intended to be authoratively substituted for Creation myths in the same way as the theory of evolution can be substituted for religious accounts of the origin of modern animals. There's really no evidence for it yet, whereas evolution is supported by vast amounts.
The point of infinite multiple universes in these discussions is that there is at least one conceivable alternative to the hypothesis that an intelligent being created this particular universe to exact specifications, and therefore the theistic or deistic view cannot be presented as the only possible way. It's the standard response to the classic argument from ignorance, or as Dawkins puts it, the "argument from personal incredulity".
In simple terms, theists will often try to prove the existence of gods by pointing to something amazing and rhetorically asking, "How else could that possibly have happened?" The obvious response, in general form: "Like this, for example." Multiple universes are one such "this".
One other alternative hypothesis which serves the above purpose is that the universe is eternal in both directions, going back before the Big Bang. This removes the need for it to be created, or to emerge, or whatever, at all. Again, no evidence yet, but not impossible and therefore lethal to any attempted proof by elimination of a god's necessity.
But let's go in another direction. We'll take your stated view a bit further and reject as implausible (though not impossible) any unintelligent, undirected origins for our universe conceived so far, including the multiple-universe idea.
Where does that leave us? With an intelligent or directed origin, facilitated by an entity which can be satisfactorily described as a god. But then where did the god come from? If no undirected origin will suffice for a collection of matter and energy capable of behaving rationally (in the absence of a clear definition of "rationally" in this context, I would have used "predictably"), what undirected origin would suffice for a fully-formed intelligent entity with the unimaginable power and knowledge required to start (and, for a theist, maintain) a rational universe? Such an entity would be even harder to make without directed labour!
One solution to this is to posit an even more powerful entity to make the god; let's call it an uber-god. If you do this, however, the uber-god itself has to have been brought about by an uber-uber-god, and so on. An infinite regress is set in motion, and we're soon drowning in ubers.
Another solution is to posit an undirected origin for the god, or a lack of origin in the case of an eternal god. But what such solution cannot then be applied directly to the universe, eliminating the necessity of the god and making for a simpler hypothesis all round?
The origin of the universe is a profound mystery indeed. It remains so because the god hypothesis is an inadequate explanation; it requires an even grander explanation for itself, or it forces you to find a viable alternative which can then replace it.