The Ancient Girl Whose DNA Revealed Her Parents Were Two Different Human Species

The discovery of Denny has implications that extend far beyond her individual existence.

She is a single data point — one individual, one moment in time, one cave in Siberia — but the implications of that data point ripple outward into questions about the nature of ancient human species and the process by which modern humanity emerged.

The first implication concerns the definition of species.

In biology, the most commonly used definition of a species is a group of organisms that can interbreed and produce fertile offspring.

Groups that cannot interbreed — or that produce sterile offspring when they do — are considered different species.