To live forever would to never be happy with another person. How could one ever find that perfect person when you are going to never age ... never die ... bury all your loved ones...

Sounds like a nightmare to me.

then have the world overrun with animals? Humans are the biggest consumer of meat in the world. Get rid of that and what do you have?

If we got rid of spiders we'd be overrun with insects. The idea is ludicrous and flat out stupid.