A new study suggests that a series of environmental changes in East Africa some 320,000 years ago challenged a previous long-standing way of life for proto-humans, and produced a more adaptable culture.

A thousand years ago, powerful Viking chieftans flourished in Norway’s Lofoten Islands, above the Arctic Circle. In an environment frequently hovering on the edge of survivability, small shifts in climate or sea level could mean life or death. People had to constantly adapt, making their living from the land and the sea as best they could.

The rise of the Vikings was not a sudden event, but part of a long continuum of human development in the harsh conditions of northern Scandinavia. How did the Vikings make a living over the long term, and what might have influenced their brief florescence? Today, their experiences may provide a kind of object lesson on how changing climate can affect civilizations.

Who were our earliest ancestors? How and when did they evolve into modern humans? And how do we define “human,” anyway? Scientists are exploring Kenya’s Lake Turkana basin to help answer these questions.