Ancient DNA Tells a New Human Story

Imagine what it must have been like to look through the first telescopes or the first microscopes, or to see the bottom of the sea as clearly as if the water were gin. This is how students of human prehistory are starting to feel, thanks to a new ability to study ancient DNA extracted from bodies and bones in archaeological sites.

A stone projectile point embedded in Kennewick Man’s 
right hip gave researchers the first clue that he belonged 
to an ancient human population; the spear point likely 
became lodged following an adversarial encounter.

Low-cost, high-throughput DNA sequencing—a technique in which millions of DNA base-pairs are automatically read in parallel—appeared on the scene less than a decade ago. It has already transformed our ability to see just how the genes of human beings, their domestic animals and their diseases have changed over thousands or tens of thousands of years.

skeleton of Kennewick Man is represented 
by nearly 300 bones and bone fragments. 
Photo: Chip Clark, Smithsonian Institution

The result is a crop of new insights into precisely what happened to our ancestors: when and where they migrated, how much they intermarried with those they met along the way and how their natures changed as a result of evolutionary pressures. DNA from living people has already shed some light on these questions. Ancient DNA has now dramatically deepened—and sometimes contradicted—those answers, providing a much more dynamic view of the past.

It turns out that, in the prehistory of our species, almost all of us were invaders and usurpers and miscegenators. This scientific revelation is interesting in its own right, but it may have the added benefit of encouraging people today to worry a bit less about cultural change, racial mixing and immigration.

A tooth from Denisova Cave in the Altai Mountains of Siberia, 
which DNA shows belonged to a previously unknown archaic 
human population, now called the Denisovans. 
Photo: Max Planck Institute

Consider two startling examples of how ancient DNA has solved long-standing scientific enigmas. Tuberculosis in the Americas today is derived from a genetic strain of the disease brought by European settlers. That is no great surprise. But there’s a twist: 1,000-year-old mummies found in Peru show symptoms of TB as well. How can this be—500 years before any Europeans set foot in the Americas?

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