To Africa, for a Family Reunion

There was once a man, says geneticist Spencer Wells, who roamed his patch of paradise in Africa some 60,000 years ago and it is to him each and every one of us today can trace common ancestry. His humble abode may have been elsewhere in the African continent, and his family tree could snake back anything from a few hundred to hundreds of thousands of years before that, we cannot be sure. What can be said for certain, says Wells in this work of population genetics, is that “all of the genetic diversity present today coalesces to a single ancestor”.

This may be an account of cutting-edge science but early enough Wells acknowledges companionship with that other connoisseur of footprints in the sands of time, Bruce Chatwin. Indeed, he likens his quest to that of the golden boy of 20th century literature. Chatwin investigated the “songlines” maintained by Australian Aborigines, a musical story etching their history before memory began. Wells says, by threading together breakthroughs in genetics, he is seeking to “resurrect a global songline”. His storytelling may be more direct, with gracious curtsies to old gods like Charles Darwin and young fellow contributors to Nature Genetics; his propensity to liken genetic diversity to variations in family soup recipes may not have passed muster with the dreamy Chatwin — but the final volume is just as enthralling, opening up our universe just that little bit more.

The stunning part is that the journey of humans — their common ancestry in Africa, then the many migratory routes they took as they spread out, beachcombing their way to varied corners of the earth — is chronicled on a microscopic patch of the Y chromosome. (Thus the title, there’s nothing sexist about it!) On little bits of junk DNA those who preceded us left chronicles of their wanderings, little imagining that genetics would enable us to translate their detours. Fascinating stuff.