Fossil fuels have powered human growth and ingenuity for centuries. Now that we're reaching the end of cheap and abundant oil and coal supplies, we're in for an exciting ride. While there's a real risk that we'll fall off a cliff, there's still time to control our transition to a post-carbon future.

Here's a look at how the massive population growth over the past 60 years has impacted the world we live in and what to expect as the world population continues to grow. Why we need so many people on the earth?