One of the lines that has always struck me is when Jeff Goldblum character said " Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should."

I read a news article today how scientists have taken DNA from 20 year old refrigerated mice and cloned them. They say it heralds the way to bring back woolly mammoths and other extinct species. I always think of that quote when i read about cloning of animals that have long past. They died for a reason and regardless of whether we agree or not they should stay dead. Nature moved on and selected the best for that distinct moment in time.