These analyses show that around 12,900 years ago, a large lake covered this area, formed by glacial meltwaters. The surrounding vegetation was very sparse, comprising a few grasses and herbs. Around 12,700 years ago, steppe (known as prairie in North America) developed – with sagebrush, birch and willow. These enabled bison to roam the area by 12,600 years ago, followed by small mammals, mammoth, elk and bald eagles by 12,400 years ago.

The authors therefore argue that the corridor only became a viable passage for human travel around 12,700 years ago, meaning it couldn’t have been the first migration route into America. Instead, it became an alternative route slightly later on.