Timelines

Tracking when humans, Neanderthals, and Denisovans crossed paths—and what became of their offspring.

- Zach Zorich

IN 1856, QUARRY WORKERS IN GEMANY’S Neander Valley discovered the bones of what appeared to have been a strange looking man. This was three years before Charles Darwin published On the Origin of Species and 15 years before The Descent of Man, so there was very little notion at the time that there had ever existed humans who were not exactly “us.” “Valley” is tal in German, and the find became known as “Neanderthal man.” Since then, countless Neanderthal sites have been found across Eurasia, and countless questions have been asked about the relationship between these extinct homininsand modern humans. For every one of these questions that has been answered through archaeology—and, in particular, via the retrieval, sequencing, and analysis of ancient and modern DNA—several more arise.

In 2010, for example, scientists confirmed the existence of another extinct hominin, closely related to Neanderthals, in Denisova Cave in Siberia, and dubbed them Denisovans. The same year, the surprising news broke that our species, Homo sapiens, had interbred with both Neanderthals and Denisovans tens of thousands of years ago. Around 1 to 4 percent of the genome of modern humans (save for that of sub-Saharan Africans, who never interacted with Neanderthals) comes from these archaic hominins. Since then, the technology and methods used to study ancient DNA have improved so rapidly that we are now able to ask questions that were simply unimaginable before. How did interbreeding affect humans, Neanderthals, and Denisovans? What genetic debt do modern humans owe to their ancient hominin cousins? What, at a genetic level, makes us human? A flurry of new studies in this fastmoving field has begun to provide some insight.