The theory known as Clovis First was the predominant hypothesis among archaeologists in the second half of the 20th century to explain the peopling of the Americas. According to Clovis First, the people associated with the Clovis culture were the first inhabitants of the Americas. This hypothesis came to be challenged by ongoing studies that suggest pre-Clovis human occupation of the Americas. In 2011, following the excavation of an occupation site at Buttermilk Creek, Texas, a group of scientists identified the existence "of an occupation older than Clovis." At the site in Buttermilk, archaeologists discovered evidence of hunter-gatherer group living and the making of projectile spear points, blades, choppers, and other stone tools. The tools found were made from a local chert and could be dated back to as early as 15,000 years ago.