Ancient American site identified in Alaska.

Radiocarbon evidence pegs a prehistoric hunting outpost situated atop a mesa in northern Alaska as the oldest "well-documented" site of human activity in North America, dating to 11,700 years ago, archaeologists announced last week at a press conference held by the Interior Department's Bureau of Land Management (BLM) in Washington, D.C.

Artifacts at the site, including about 50 expertly sharpened stone spear points, belong to a culture previously unrecognized by archaeologists, contends BLM's Michael Kunz, who discovered the "Mesa site" in 1978. This supports the theory that groups with different cultural heritages crossed a land bridge from Siberia to Alaska around 12,000 to 14,000 years ago and led distinctive ways of life in their new homeland, Kunz says.

His interpretation of the Mesa site enters an often fractious scientific debate regarding when the first people arrived in North America and how they got here (SN: 6/9/90, p. 360).

"The Mesa site is important and deserves further investigation," notes Robert Ackerman, an archaeologist at Washington State University in Pullman. "But it's an open question whether it's the oldest human site in North America or contains the remains of a distinctive culture:'

Kunz discovered the Alaskan site while conducting a federally mandated archaeological survey of the area prior to oil and gas exploration. Richard Reanier, an archaeologist at the University of Washington in Seattle, joined him for excavations.

Along with the spear points, Kunz and Reanier recovered stone tools associated with the manufacture of hunting weapons. For instance, a "graver" with a sharpened edge was probably used to cut strips of rawhide for fastening spear points to wooden shafts. And hunters may have fashioned spear shafts with stone flakes found at the Mesa site.

"Ancient hunters probably climbed up the 200-foot-high mesa to get a good view of game animals on the landscape and worked on their weapons there:' Kunz asserts.

Kunz delayed announcement of the Mesa finds until he received what he calls "bulletproof" age estimates for the site. A series of 13 radiocarbon dates for bits of charcoal found by the researchers, including 11 dates produced by a technique that relies on a high-energy mass spectrometer to separate and count carbon atoms of different mass, range from 9,700 to 11,700 years old.

The latter date exceeds by several hundred years the oldest remains of Clovis hunters, long regarded as the first inhabitants of North America, Spear points at the Mesa site differ significantly from those found at Clovis sites, Kunz maintains, and represent the handiwork of an unknown culture.

Several Alaskan sites contain stone tools of the 11,000-year-old Nenana culture; these tools show similarities to implements once used by eastern Siberian peoples. No Siberian parallels exist for Mesa or Clovis remains, Kunz says.

"The settling of the New World was more complex than many archaeologists thought," Kunz argues. "Two very different cultural groups were present very early on, and there may have been more:"

Rather than migrating to North America in several waves, as some investigators have theorized, nomadic hunters probably "dribbled" across the ancient land bridge in pursuit of game and ended up on the new continent by accident, Kunz proposes.

However, it remains unclear when people first reached the New World, Ackerman says. Human remains in Pennsylvania and Chile date to 12,000 years ago, and another Alaskan site dates to 11,750 years ago. Ackerman considers these estimates as valid as those for the Mesa site. Even earlier sites may exist, especially in poorly explored regions of Alaska, he says.

Archaeologists must find more Alaskan and Pacific Northwest sites to determine whether the Mesa weapons hail from a separate culture, Ackerman adds.