Ok, this is a good one to start my Saturday morning here.... (9am local time).
First the second question, for that is the easiest one.
Whether the glass is half full or half empty depends on the situation. Of course, psychologists would state that (s)he who says that the glass is half full, is an optimist, whereas (s)he who says the glass is half empty, is a pessimist.
However, when you add the word 'only' to it, what is seen as optimistic first, can turn into something negative. Let me explain:
When you are enjoying a nice glass of, let's say, beer. Someone just filled it up, but only filled it up half. You would say "that glass is only half full", implying that you didn't get what you wanted and want more, hence, a negative remark.
I always look at this from the original situation. Hence, when the glass was empty first and is now refilled to half its contents, it is half full; when the glass was full and someone drank half its contents, the glass is now half empty.
As to your first question, that answer is not really that hard and can easily be found by using google...sorry to disappoint you.
Here are a few links that turned up when entering the question in the google search bar (yeah, search rules everytime ):
But then again, there are so many different views to this question, a scientific one, a Darwinist one, an an evolutionistic one etc. So in a sense you asked a question to where different people have different answers and it is not as easy as I stated earlier.
But since I believe in science and not in one God who created all and feel that the Darwinist view is the evolutionist view and they are both based on a scientific view, the answer explained in the first link is the true answer to the question "What was first, the chicken or the egg".
Sorry if I have spoiled it for the rest of you now