The traditional story of the peopling of the New World holds that ancient migrants out of northeast Asia slipped into the Americas bearing finely shaped stone projectiles, so-called "Clovis points," after the town in New Mexico where they were first uncovered. This Clovis culture rapidly spread throughout the empty continents and by 1,000 years after their arrival had reached the southernmost tip of what is now South America, making them the original ancestors of indigenous Americans. A number of controversial archaeological sites have challenged this theory and now, by using more advanced dating techniques, researchers may have killed it, throwing the original population of the Western Hemisphere into question again.

Geoarchaeologist Michael Waters of Texas A&M University and radiocarbon specialist Thomas Stafford of Stafford Research Laboratories reexamined 22 Clovis sites that had previously been dated. Half proved suspect because they lacked direct evidence or had other conflicting data. "Over the years, scientists, if they have a site that dates 11,000 years ago, even if they just found a few flakes and a scraper, they automatically called it Clovis," Waters explains.

That now appears in doubt, as Stafford and Waters have succeeded in dating five of the remaining sites more accurately thanks to improvements in the technology of radiocarbon dating. Using atomic accelerators and collagen purified in molecular sieves, the two found that the Clovis artifacts they dated all occurred within 11,050 radiocarbon years to 10,800 radiocarbon years before present. "Just a duration of about 200 years with a maximum duration of 350," Waters says.

That means Clovis sites are contemporaneous with some undisputed sites in South America and younger than some in North America. It also makes it difficult to understand how an ancient people could have spread so far in such a limited amount of time, let alone how the Clovis point [see image above] people could have spread throughout the U.S. "That raises the question: Is it a people or a technology?" Waters asks. "That kind of rapid spread of technology is almost unprecedented. Metallurgy moved very quickly, gunpowder and things like that, but that was a different time."

"This revives the old concept of a technology spreading across a population base," he continues. New evidence seems to point to humans populating the Americas as far back as 25,000 years ago and it may be that the Clovis points were simply a superior weapon that spread rapidly from people to people. But scientists need to come up with a new explanation for the original American settlers that incorporates this new archaeological data as well as genetic and geologic evidence. "I think we need to stop thinking about the peopling of the Americas as a singular event and start thinking about it as a process," Waters says. "I think there's enough evidence now to say that there were pre-Clovis people in the Americas."