This is awesome of him to do. And as an aside, Robert J. Sawyer’s Neaderthal Parallax trilogy is one of my favorite sci-fi trilogies ever. It’s about a team of Canadian physicists who accidentally open a portal to an earth in a parallel universe where Neanderthals became the dominant species on the planet. The series explores how their modern society may have evolved and how their technological and social development may have differed from our own. I highly recommend it for fans of hard sci-fi and alternative history.