I am but a simpleton. Here's my take on this issue:
Be a good steward; don't waste resources, do the things that make sense for everyone, not just yourself. Take care of your trash, and keep your car/ furnace/ other fossil fuel engines in good condition. Yes, it costs time and money to do so, but do it.
As long as we keep having babies, and utilizing medicine to live longer, we have to accept a certain amount of these issues. The population will continue to grow. People will use more space, energy, etc.
No one knows what happened 500,000 years ago, nor do we know what will happen 500,000 years from now. Live responsibly now, and teach the next generation correctly.