It's easy to forget sometimes that science is a process. It's a methodology for understanding the world as best we possibly can, through evidence, data, testing, re-testing, analysis, and following the leads that evidence and facts provide.
For scientists, making a discovery that upends much of what was previously known has to be one of the most exciting things that can happen. For the rest of us, it can be a bit frustrating. Just when we thought we knew something, we find out it's not the case. But that's just how it goes with science - new data can really change things.
Now, one new discovery has scientists re-evaluating a pretty major belief about how and when humans started spreading around the world.