Just listened to an interview with Ridley Scott. Couple of things I didn't come away from the film with, but maybe I would on another viewing.
1) The goo kills the town square full of Engineers instantly. It's basically a plague and kills all animal life on the planet, including all of the Engineers not right there. That's why there's no animal life when they arrive.
2) It's an anti-religious message. The acting captain, who talks about his faith a lot, is the one who makes most of the stupid decisions. His second in command is much more competent and objects to his decisions.
3) He believes David because until that point he still instinctively trusts synthetics.
4) I don't think he's seen Alien 3 and Resurrection from what he was saying, and isn't too keen on the lore that Cameron added. I suspect we won't see another Queen.
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