Ric asks:
" If there is a "God"-- an omnipotent being who had the power to create the whole universe singlehandedly-- why wouldn't he have the power to create all the complexities we discover in it?"

Well of course he would. No question about it. But if he did then he would know about penicillin. He would therefore have the opportunity to make one of the following two conscious choices.

1. Tell people to prevent the unnecessary painful suffering and death of billions.

2. Keep it a secret and let people, thousands of years later, find it for themselves.

The first choice would demonstrate a god that cared about his creations, valued life, and saw as horrible the suffering of innocent young children.

The second choice would demonstrate an unfeeling, uncaring, or malicious monster.

Choice is yours. Knew and didn't tell, didn't know, or doesn't exist. There are only three possible choices. Pick yours with care.
DA Morgan