Arrowhead battles

Does your heart swell with pride every time you think of those sturdy first immigrants, ancestors of today's Amerindians, who walked over the land bridge from Siberia hunting wooly mammoths with stone-tipped spears as they came? Would it deal a serious blow to your sense of self-worth to discover that those first comers took a boat and dug clams, instead?

Brace yourself: A corps of archaeologists armed with spades and obsidian spear-points is preparing to overturn the received wisdom regarding the peopling of the Americas. And they're facing stiff opposition.

In "Lost World," journalist Tom Koppel gives us not merely good reporting on field archaeology in action, but a blow-by-blow account of a major scholarly battle in full spate. When it comes to landing knockout punches, Mike Tyson has nothing on Koppel's account of archaeologists dealing near-fatal blows over dating methods.

The archaeological record in the Americas begins with a scattering of stone spear tips known as Clovis points. These distinctive artifacts have been found from the Atlantic to the Pacific in such numbers that you can easily see one in a nearby museum. Even a brief inspection separates the distinctively fluted Clovis points from the arrowheads in the display case. Indeed, their distinctiveness establishes that all Clovis points were made by a single, big-game-hunting culture.

The charcoal and bones found with them prove that Clovis culture was spread rapidly across North America from 12,800 to 13,200 years ago by hunters who used stone-tipped spears to kill animals like the giant buffalo and mastodon.

The great question is: Did the Clovis walk over the land bridge, or did they evolve from an earlier Amerindian culture, possibly a population that moved along the Pacific coast in canoes?

Koppel, a strong partisan of the canoes-along-the-coast theory, lays into the "stubborn, hidebound" academic proponents of the walked-over-the-land-bridge hypothesis with the vigor of a hungry Paleo-Indian attacking a woolly mammoth.

The advantage of the coastal migration theory is that it makes sense. Life along the littoral is easy. Oysters, after all, just lie there waiting for someone to eat them, and even an animal as large as a sea lion makes easy prey when it hauls itself onto a beach. When the coasts of Alaska and British Columbia got overpopulated, it would have been the easiest thing in the world to climb into a canoe and move on to an empty beach along Puget Sound, or San Francisco Bay, and so on right down to the tip of South America.

Well and good. But the question that troubles those "stubborn, hidebound" academics is that despite the compelling logic of the coastal migration theory, its proponents have turned up very little in the way of evidence.

To argue that the first Americans followed the coastal route is to assume that people lived at the shore for some period of time before developing the Clovis hunting technology and moving inland. Yet no human bones older than Clovis have ever been found in the Americas. And there are only two archaeological sites believed to pre-date Clovis: Monte Verde in Chile and Meadowcroft in Pennsylvania. What's more, most archaeologists have serious doubts about Meadowcroft.

This raises critical questions since sites this old are not rare in the rest of the world. Australia alone has 200 well-dated sites older than Clovis.

In recent years, archaeologists intrigued by the coastal theory have headed for the rain-swept northwest coast to reconstruct prehistory, piece by soggy piece.

Koppel follows archaeologist Tim Heaton deep into a narrow cave on an island off the coast of British Columbia. We see Heaton reaching under a rocky ledge, "digging in soupy sediments, working mainly by feel. Suddenly, nudged by his trowel, a long, narrow piece of bone flipped into view" - the oldest human bone yet found on the Pacific coast.

It turns out to be not quite old enough. Yet I finished "Lost World" excited by the prospect that this summer or next, an archaeologist on an island off Vancouver will reach into a layer of damp sediment to pull out the definitive piece of evidence. Koppel's book will prepare you for that round.

• Diana Muir is the author of 'Reflections in Bullough's Pond: Economy and Ecosystem in New England' (University Press of New England).