Between 9,000 and 13,000 years ago, bison were attracted to extensive wetlands to the west of what is now the city of Socorro, in central New Mexico USA.
     In the year 2000, archeologist Robert Dello-Russo and his team discovered a major archaeological site while surveying part of a 36 square kilometre field laboratory belonging to an explosives research company which has hosted several episodes of the Myth Busters television series.
     Since then, Dello-Russo and his colleagues have returned to the Water Canyon site repeatedly. Finds include spear and/or atlatl points from the Clovis people, who hunted here more than 13,000 years ago, from the Folsom people who hunted here more than 12,000 years ago, from the Cody Complex hunters who butchered bison and left the bones around 10,800 years ago, and from the late Paleo-Indian people around 9,200 years ago. Dello-Russo and his collaborators have also found gypsum points from the Middle to Late Archaic people.
     Blackwater Draw, the Clovis Site in eastern New Mexico, is the first in the state where it could be documented that generations of Paleo-Indian hunters killed their prey and returned to the place again and again. Water Canyon appears to be the second.
     The site may offer the opportunity to understand how bison evolved. "There is this evolutionary trajectory from the late Pleistocene where bison go from being Bison antiques, which is a species that was 10 to 20 percent larger than modern day bison, to the Holocene when they became the smaller, modern bison or Bison bison," says Dello-Russo.
     Dello-Russo also found something at the Water Canyon site called a "black mat" - a buried layer of sediment with a high degree of organic matter that represents the remains of the prehistoric wetland.
     "Today this land is what's called a juniper savannah. A very dry grassland. It gets about 8 inches [20 centimetres] of rain a year, maybe," Dello-Russo said. "Back then they probably got triple that amount of moisture. There was probably standing water in some places, flowing in other places. The vegetation included things that we don't have there today, such as versions of maple trees and birch, cherry. We used to think it was like a forest of actual trees, but we are beginning to think it was a more shrub-like environment."

Edited from PhysOrg (18 March 2016)