One ancient language transformed our world. This is its story. As the planet emerged from the last ice age, a language was born between Europe and Asia. This ancient tongue, which we call Proto-Indo-European, soon exploded out of its cradle, changing and fragmenting as it went, until its offspring were spoken from Scotland to China. Today those descendants constitute the world's largest language family, the thread that connects disparate cultures: Dante's Inferno to the Rig Veda, The Lord of the Rings to the love poetry of Rumi. Indo-European languages are spoken by nearly half of humanity. How did this happen? Laura Spinney set out to answer that question, retracing the Indo-European odyssey across continents and millennia. Spinney meets the scientists on a mission to retrieve those lost languages: the linguists, archaeologists and geneticists who have reconstructed this ancient diaspora.