No, it’s true. All humans (and that means you) are descended from just one woman and just one man, but they missed each other by thousands of years.
No, really, it is possible. It happened like this.
Imagine a band of humans, the only ones in the world. There are only three women in this band, and, as the fates decree, only one of them has grandchildren.
That soon means, of course, that everyone in the world is descended from a single woman.
Thousands of years later, humans are again reduced to a very few individuals. There are only a couple of men in the world, and only one of them has grandchildren.
That soon means, of course, that everyone is descended from one man.
It also means we’re all very, very, very lucky to be here.
Aren’t we, cousins?