Hank Green, from SciShow, explains how researchers got the idea that an asteroid killed the dinosaurs 65 million years ago and why that is not the whole picture. It seems that the asteroid was the last drop in the bucket and that climate change, volcanic eruptions were the ones that started the extinction.
The asteroid came to finish a job that was already started by Earth changes. While the asteroid theory seems compelling we need to look at the bigger picture. Could we survive should such an asteroid hit Earth again? Some of us yes as we have the tech to live underground for many years, but it would be a big cost for humanity.