The late esteemed English actor Christopher Lee traced his ancestry directly to Charlemagne. In 2010 Lee released a symphonic metal album paying homage to the first Holy Roman emperor—but his enthusiasm may have been a tad excessive. After all, says geneticist Adam Rutherford, “literally everyone” with European ancestry is directly descended from Charlemagne.

The family tree of humanity is much more interconnected than we tend to think. “We’re culturally bound and psychologically conditioned to not think about ancestry in very broad terms,” Rutherford says. Genealogists can only focus on one branch of a family tree at a time, making it easy to forget how many forebears each of us has.