Why did early humans have perfectly straight teeth?

Sure, we may have all of the amazing technology, but early humans had it made. Who needs the internet when you don't have to worry about a job or taxes? Hate lines at the DMV? May I present to you the idea of living in a community that has all of your necessities within walking distance? On the one hand, Diseases and wars back then were horrific, but at least you didn't have to worry about the constant threat of WW3. At that point, you just had to brace for the looming impact of the Crusades in a few centuries.

Obviously, I'm joking, but our early ancestors did have a few biological benefits that many of us would kill for in modernity. Take their preposterously straight teeth, for example. In the video linked above, you can find out why prehistoric humans had such perfectly straight teeth in opposition to the misaligned mouths we have today.