Scientific American Frontiers . Coming Into America. Clovis First?


		Using broken mammoth bones, Steve Holen of the Denver Museum of Nature and Science believes he can push the peopling of America back as far as 18,000 years ago.

As Alan learns, several new discoveries have called the Clovis-First theory into question. One site, Monte Verde in Chile, has been controversial for many years. It's at least 1,000 years older than Clovis. Another site, Topper in South Carolina, offers evidence that people lived in the forests of eastern North America long before that.

In 1981 a local named John Topper told archeologist Al Goodyear about a source of flint he had found near the Savannah River. Al Goodyear has been working to uncover the history of the site ever since.

At first, the Topper site seemed a textbook story of early life in North America, with Clovis the earliest inhabitants. But in 1998, inspired by the Monte Verde discovery, Goodyear decided to look deeper, into a layer of Ice Age river sand.

The dig uncovered many ancient tools, with the prize find named the "Topper Chopper." Using a technique called OSL that precisely measures the light energy stored in sand, scientists dated the layers directly above where the tools were found at 15,000 years old. This means the Topper Chopper is even older.

Steve Holen of the Denver Museum believes he can push the peopling of America back even further--as far as 18,000 years--with the aid of broken mammoth bones uncovered at five sites in the US. Critics say the bones could have been broken by animals, but Holen shows Alan why he thinks that's impossible.

By studying the way a lion chews on a bone, scientists can ascertain that 18,000-year-old mammoth bones must have been crushed by humans.

At the Denver Zoo, Alan looks on as first lions, then hyenas chew on cow leg bones. After several hours, there's little damage. The hyenas, probably the most powerful bone crunchers around today, chew away the ends of the bones but can't get into the thick middle sections. Paleontologists say bigger prehistoric animals like the plains lion and the giant short-faced bear couldn't have done much better. Adult mammoth limb bones, they say, were just too heavy and thick.

Holen has Alan smash a cow bone using a hammer stone, as the early Americans would have. The pattern of the resulting "spiral fracture" matches those found on the ancient mammoth bones-proof, says Holen, that humans broke them 18,000 years ago.