"Having said this, I'd be REALLY interested in your ideas for a hypotheseis to test how a caterpillar could evolve the DNA necessary to turn into a butterfly, through small mutations and natural selection. A lot of what purports to be science is really just 'faith' based guesswork, and would be called such if it were not for the big names spouting it."
Here is a great place to start: http://www.scientificamerican.com/article/insect-metamorphosis-evolution/
Short answer: we don't have all the pieces of that puzzle yet. That doesn't mean we won't get there. It just means you are pointing to a current area in which our knowledge is incomplete and saying "hah, god must exist, because you don't understand this fully!"
There's nothing rational about that. If I pour a half-filled wide-brimmed cup of water into a tall, short-brimmed cup and it fills the cup, a young enough child will think it magic. They don't understand the conservation of volume.
I could tell the child that it is god that does this, and that he should accept that it is god because he doesn't understand how it is possible for such a thing to occur.
Alternately, I could set up some experiments by which the child could play with moving a volume of liquid around different containers for himself and allow him to understand the concept of conservation of volume through experimentation.
In the first instance, the child's understanding stops at the moment faith is injected. God is the answer and thus no further questioning is required. In the second instance, the child learns something about the world, god is not required and the child is one step closer to being able to formulate his own questions, craft his own hypotheses and experimentally test to see what may or may not be the reason behind something.
"What force started the big bang?"
Ultimately, we don't know. String theory has some neat ideas, but they are as yet something we cannot prove. Why should I believe this "proves" god, rather than is simply evidence of a gap in our knowledge?
Where is the evidence that a gap in our understanding of the universe means god exists?
"How did chemicals gather to create life?"
Interesting you should ask. Please read all my other posts in this particular comment section for the answers. I've covered it many times. There are also links to lab-created artificial metabolisms. To be perfectly honest, I am absolutely convinced that - given the progress we've made thus far - we will have recreated the early mechanisms for life creation and created fully artificial life in the lab within my lifetime. This is no longer a question of "if", but of "when".
"How did a single cell organism become a multi-cell organism?"
You can start here: http://en.wikipedia.org/wiki/Multicellular_organism#Evolutionary_history
But I'll do you a favor and summarize it for you. The long story short is that single-celled organisms have a long history of living together, frequently in what are typically referred to as "mats". The short version is that "mats" of single-celled organisms are far more efficient at using their environmental resources - and responding to dangerous events, like toxins - than cells are on their own.
Bacteria also evolved the ability to exchange DNA long before multicellularity evolved. In large part, this was an evolutionary adaptation to cope with viruses. They also evolved the ability to create bacteriophages: essentially viruses that seek out and destroy bacteria that the originating bacterium doesn't like.
Over time, cells accumulated enough DNA from their "chosen" companions that they could theoretically perform the functions of any of a number of different types of cell. This doesn't mean they would, but merely that their DNA contained the information.
Eventually, a freak of evolution occurred: cells gained the ability to alter their functionality based on environmental/epigenetic factors. A cell in the middle of the mat would perform one set of functions. A cell on the outside would perform another.
Once cells had reached this point, they had no need of other species. So, to put it midly, they killed them off. Life is about the propagation of your own genetics, after all.
One cell, with one set of DNA could perform multiple functions in the mat. It could reproduce it's own lineage and that lineage could do everything required to take advantage of the environment. It didn't need to devote any resources to helping another species - or another individual - survive.
Some time after this, these single-species mats began rapid specialization, and things like "an outer protective layer that encloses all of the organism's cells" were developed. This helped separate the organism from it's environment more completely, and helped prevent other organisms from invading the mat and stealing resources. Thus a multicellular organism is born.
I am aware of at least 15 different instances in our evolutionary record in which multicellular life evolved independently. There are probably more.
"What is the origin of Sexual reproduction?"
Well that is an operation in semantics. Do you mean the evolution of modern genetalia? There's a fish responsible for that one; in fact, it's genital claspers eventually evolved into our legs.
Do you mean simply the combination of two gametes to form an offspring? That's more complicated. I'm a little rusty, but here's my understanding:
Sexual reproduction had to have evolved at least 1.2 billion years ago. All sexually reproducing creatures share a common ancestor, and that ancestor developed sexual reproduction before it developed multicellularity.
The theory goes that while other groups of single-celled organisms were developing into bacterial mats - and eventually multicellular (typically multicellular + symbiont) life - our ancestor solved the same set of evolutionary circumstances in a completely novel way.
Instead of inducing horizontal gene transfer with another bacterial species, it "unzipped" it's DNA during mitosis, and didn't "zip" it back together. That's one hell of a mutation: it basically turned DNA back into RNA!
Now, single stranded DNA is highly unstable. It's not remotely as conducive to life as double-stranded DNA. It is, however, possible for cells to live - and eventually to divide - using RNA instead of DNA. The mitochondria is a great example of a cell that did this (before it invaded us!)
But DNA is better. Eventually, two of those RNA-only cells recombined and merged their genetic structures. The result was a randomization of genetics, or...sex.
So this strand of life solved the need to rapidly respond to environmental changes by evolving the ability to unzip itself, split in two, then re-merge, randomizing genetics. We have no hard data on how long that went on before it also underwent the evolution to multicellularity, but it was probably quite a while.
The long story short is that when multicellular organisms arose from that particular branch of "unzipping" single-celled organisms, they took with them the concept of sex. It was rather a long time before that evolved into what we think of as genitalia, but the progression was fairly straightforward.
"You say: What's more, why you[r] god, and not someone else's? Why your interpretation of how god works, and not mine? Why one god and not many?" Again, that's a theological question, not a scientific one. I have many reasons why I am trusting in God, I'm happy to elaborate based on logic and my experiences to anyone who wants to hear."
No, it's a scientific question. Science needs to know what it's testing for if it is to look for it. You don't just say "I am looking for a new particle". You do the legwork to figure out what the particle should look like, it's mass, behaviour, composition and decay vectors. Then you have something to look for and go look for it.
There are many different gods described. They're all different. Evidence to support their existence would therefor reasonably be different. Don't dodge the question just because it's uncomfortable, or try to make this about "science versus god" when you aren't presenting scientific evidence for both the existence of your deity and why your deity is the "correct" one.
Facts, not faith.