IT ISN'T AN EASY DRIVE from Alberta to Baja California, but Ruth Gruhn and Alan Bryan, archaeologists from the University of Alberta (and husband and wife), have been making the journey since 1991. The barren desert peninsula is the spot they chose to test the theory that the earliest settlers of the Americas traveled by boat, not on foot. Their excavations at two rockshelters have yielded tantalizing results. They have found evidence of human occupation at the early Holocene--about 9000 RCYBP (10,500 calendar years ago)--and they have hopes of pushing dates back even further.

Why walk when you can paddle?
The theory they are testing is the coastal-entry theory of migration, first proposed by archaeologist Knut Fladmark of Simon Fraser University nearly 30 years ago. Dr. Gruhn supported the theory more than a decade ago, before the collapse of the Clovis-First model--and even made a convert of Dr. Bryan. In recent years increasing numbers of North American archaeologists have become supporters of the theory.

The coastal-entry model cuts through complicated theories contrived to explain how humans crossed the Bering land bridge on foot, how they found a route through the Cordilleran and Laurentide Ice Sheets to the temperate areas of North America, and what they found to eat during their journey. Even enthusiastic Clovis-First advocates admit it wasn't an easy journey, and the timing was crucial, since their model depends on an Ice-free Corridor between the glaciers at the time of the supposed trek.

Why couldn't the first Asians have made the trip by boat instead? Dr. Fladmark contends that the trip would have been possible anytime during the last 60,000 years. Smithsonian archaeologist Dennis Stanford points out that "everyone knows boats have been around for 50,000 years" (MT 17-1, "Immigrants from the Other Side?"). It needn't have been an unremittingly arduous journey, since the coast along the Pacific Northwest had ice-free pockets that could have provided relief for southbound voyagers. And instead of relying on megamammals for food (that image of the Paleoamerican hunter with spear stalking woolly mammoths is a hard one to shake loose), the colonizers could have been conditioned to subsisting on bounty furnished by the sea--mollusks, fish, and the birds and mammals that fed on them.

The coastal-entry theory has an especially attractive advantage over models that have humans traversing the continent--and the entire hemisphere--on foot: speed. Paul Martin's prehistoric-overkill hypothesis, for example, contends that humans made the crossing from Beringia about 12,000 RCYBP (14,000 calendar years ago), then developed sophisticated stone-tool technology that made possible rapid population growth. Martin believes that, thanks to their efficient hunting tools, the first Americans reached the tip of South America as early as 1,000 years later. For Fladmark's boat people, that's a snail's pace. "Even primitive boats," he submits, "could traverse the entire Pacific coast of North and South America in less than 10-15 years."

Central and South American sites can't be ignored
"It is very clear that South America," Gruhn insists, "in all the major environmental areas, even the tropical forest and southern Patagonia, was already settled by Clovis time in North America." She points to Monte Verde, the site in Chile excavated by University of Kentucky archaeologist Tom Dillehay, which dates to 12,500 RCYBP, or about 14,700 CALYBP. (The validity of the Monte Verde finding is still contested by some archaeologists.)

Gruhn names other sites--Taima-Taima in Venezuela (which she excavated with Bryan), with a date of 13,000 RCYBP, or about 15,500 CALYBP; and several sites in Patagonia with dates around 12,000 RCYBP, or about 14,000 CALYBP. She speaks with authority. In 1969 and 1970 Gruhn and Bryan drove their brand-new Land Rover through Central America, then hopped a ship to Venezuela and drove to Patagonia and Brazil. They visited just about every early site known at the time, making connections and laying the groundwork for future research.

For a good overview of South American sites that show promise of expanding our knowledge of the peopling of the Americas, Gruhn recommends The First South Americans by Danièle Lavallée, whom Gruhn met at a conference in Belgium. Although Lavallée has explored sites in Peru, that isn't the topic of her book, nor is it her strength. "She is European," Gruhn explains, "and has a different perspective on American prehistory."

Why did Gruhn and Bryan choose Baja California as the place to test the coastal-entry theory? Glaciation during the Pleistocene produced great changes in sea level, down 130 m (450 ft) at the Last Glacial Maximum. Consequently, the Pacific Northwest as far south as Washington experienced radical changes in its coastline. Any evidence of early travelers would likely have been either submerged by elevated waters or obliterated by shifting and melting glaciers. (Archaeologist Daryl Fedje retrieved a stone tool from the ocean bed, 175 ft down, while dredging a riverbank 11,500 calendar years old in the Queen Charlotte Islands of Canada. It's certain he would be the first, though, to declare the working conditions less than ideal.)

Abrigo Paredón is the space defined by three enormous bloulders. The largest dwarfs volunteer Jim Wilson. ~ photo by Alan Bryan
Baja California is a good fit. The peninsula is remote and sparsely populated. Because the ocean floor drops off sharply, changes in sea level had little effect on the contours of its coastline; the shore today looks quite the same as it did in the Pleistocene. Other scientists have made cursory explorations of Baja California since the 1950s and found intriguing artifacts. In 1952 Aschmann reported the discovery of fluted points in the northern part of Baja California Sur, and in 1957 Brigham Arnold found large bifaces on old lake beaches that he suspected might date to the Pleistocene. Don Tuohy, who had made several trips to the interior in the 1950s, accompanied Bryan on an exploratory tour of the entire peninsula in 1991. In 1997 Gruhn and Bryan received a permit from INAH (Instituto Nacional de Antropología e Historia, pronounced EE-nah, the Mexican national archaeological agency) and, with graduate student Loren Davis, launched a geoarchaeological study of the Laguna Seca Chapala basin, a dry lake bed (playa). The pilot project led to the discovery of Abrigo Paredón, the first of two rockshelters, and work in Baja has continued ever since.

Their work is highly focused. Previous finds were surface-collected, Gruhn notes, and therefore lack provenience and dating. What is more, the discovery of Clovis fluted points merits only passing interest. If their theory holds true, they expect to find evidence of a culture that predates Clovis, that of "generalists who had long exploited the productive Pacific coastal ecosystems with a relatively simple lithic technology." The earliest colonizers would probably have supplemented their tool kits with implements made of shell and wood; like boats of animal skin and wood, however, these objects are unlikely to have survived over the millennia.

Abrigo Paredón
The first rockshelter Gruhn and Bryan xplored isn't much to look at, just three enormous boulders at the foot of a slope overlooking Laguna Seca Chapala 100 m (330 ft) off to the northwest and 3.5 m (11½ ft) below. A small alcove could shelter one or two persons, "but it leaks," Gruhn notes wryly. Its best feature is shade, a precious commodity in the desert. Campers using it today have made a stone-lined firepit and strewn their garbage about.

Early people also welcomed relief from the sun. Excavations started in 1997 and continued in 1999 reveal that the rockshelter served as a flintknapping station. The entire basin is granitic, Gruhn explains. Weather exfoliates the boulders, crazing and pulverizing their surface. "In some places," she notes, "it looks as if someone backed up a truck and dumped a load of gravel." About 10 or 20 minutes' walk from the rockshelter are a series of felsite dikes that traverse the granite bedrock. Felsite is a very fine toolstone, fine grained and quite flakable. Knappers collected felsite blanks at the dikes, then brought them back to the rockshelter. In a comfortable setting they worked the blanks into smaller, thinner bifacial preforms, then into projectile points and knives.

Excavations carried to a depth of 55 cm (22 inches) below surface uncovered the products of long-term occupation: many foliate (leaf-shaped) projectile points and preforms, and "tons" of knapping flakes--about 25,000. Also found were thick scraper planes and humpbacked-core scrapers. A type common in the region, they have flat platform faces and steeply retouched peripheries, sometimes with noses or sharp graver spurs. Gruhn and Bryan suspect they were used to work wood or to process agave for fiber.

Gruhn (standing) and U.S. and Canadian student volunteers work at Abrigo Paredón in 1999. That's Laguna Seca Chapala in the background. ~ photo by Alan Bryan
Abrigo Paredón resists precise dating. The artifact-bearing stratum is brown sandy silt. The upper 20-25 cm (8-10 inches) has been extensively disturbed by burrowing rodents and insects; the texture of the silt suggests it was deposited by the wind and by slopewash, and high winds and heavy rains have likely scoured and eroded the site. Stratification is therefore absent, but charcoal samples from 20-50 cm (8-20 inches) date between 6800 ± 580 and 9070 ± 60 RCYBP. Sand and silt apparently began accumulating in the early Holocene.

Among the few animal remains found in the brown sandy silt at Abrigo Paredón are bones, mostly of hares, but also of large grazing animals like deer, evidence that Chapala once held enough water to support wildlife. "Certainly there were pluvial lakes in what is now desert in Baja," Gruhn remarks. She knows of several others besides Chapala. "Lakes, or even marshes, would have attracted wildlife and humans to exploit it in the late Pleistocene and early Holocene."

In recent times, Baja California has shown a tendency to revert to a wetter state. A few months before Gruhn and Bryan arrived for the 1997 season at Abrigo Paredón, a hurricane had crossed the peninsula and deposited about 8 inches of water in Chapala. "Normally we drove right across it to set up camp," Gruhn reflects. "Oh no, this time we had to work our way around it." Storms in November and December blew down tents and made mud so deep one of their vehicles got stuck. To live or even work in this land, you have to pay a price.

Abrigo de los Escorpiones
Excavations at Abrigo Paredón found sterile cemented gravel 55 cm (22 inches) below surface, and a backhoe trench 4 m away hit sterile cemented sediments at 1 m (3¼ ft). Convinced that Abrigo Paredón had no more stories to tell them, Gruhn and Bryan moved to the Pacific coast. They led a crew from the University of Alberta that started digging in 2000 at Abrigo de los Escorpiones, a rockshelter formed by the high overhang of a volcanic outcrop about 100 m (330 ft) from the rocky Pacific shore.

Unlike Abrigo Paredón, which played out when only 2 ft deep, Abrigo de los Escorpiones didn't get exciting until they reached 6 ft deep!

Abrigo de los Escorpiones. The volcanic outcrop forms an overhang; much of the recess underneath in the northwest corner (marked by the test pit and ladder) has been filled by vast deposits of shells. By excavating back under the overhand, Gruhn and Bryan hope to find evidence of Pleistocene occupation. ~ photo by Alan Bryan
The sheltered area of Abrigo de los Escorpiones, about 1-3 m wide (3.3-10 ft), extends 35 m (115 ft) and slopes down to the west (toward the ocean) and south. Most of the sheltered area surface is rock rubble except for the northwest quarter, which is a shell midden. Shell fragments are exposed on the surface far down the slope. The excavations in 2000 were made at the northwest end of the rockshelter through the midden deposit. One test pit was dug in increments of 10 cm (4 inches) to a depth of 5.3 m (17½ ft). Although there was at least another 2 m (6½ ft) of rock rubble overlying bedrock, no more undistrubed cultural materials were found, and the excavations were filled with hay bales and covered with dirt in anticipation of resuming work in 2001.

Vandals visited the site, however, and disturbed the upper 6 ft of the excavations. The mischief-makers unwittingly did Gruhn and Bryan a favor, because in digging out to the north to stabilize the walls of the test pits, they found that the rockshelter opened up--the sheltered area expands toward the north under the overhang. Excavations in 2001 reveal that Abrigo de los Escorpiones, a much larger rockshelter than was first apparent, has been completely filled by a shell midden that overlies sterile silt and heavy rubble.

The shell midden has three distinct stratigraphic zones. The uppermost, to a depth of 2.8 m (9¼ ft), consists of mottled brown silt containing shells (mussel, abalone, and marine snails) and fish bones. Since the area lies directly under a raptor's perch, there are also bones of small mammals and birds that were the bird's prey; identifying them will inform us about the paleoenvironment. The uppermost zone also yielded many lithic artifacts including large unmodified flakes (most common), flaked cobbles, cores, choppers, hammerstones, manos, milling stones, and retouched or utilized flakes.

The middle zone is compact black/brown ashy silt about 1.5 m (5 ft) thick that slopes down to the north and west under the overhang into an area not yet excavated. Distributed throughout this zone are the same kinds of shells found in the uppermost zone, besides clams, giant chitons, and limpets in the lower levels. Besides lithic artifacts like those in the uppermost zone, Gruhn and Bryan also found several large lanceolate projectile points and substantial flaking debitage. Samples from the middle zone were dated at 6340 ± 100 RCYBP at a depth of about 2 m (6½ ft), and 8040 ± 70 RCYBP at a depth of about 3.5 m (11½ ft).

Working at Abrigo de los Escorpiones in 2000, the first season. Ruth Gruhn is doing a profile in the test pit, about 16 feet deep at the time. (Just visible is a bucket at the bottom.) ~ photo by Alan Bryan
The lowest midden zone, brown loamy silt with rubble about 1 m (3¼ ft) thick, slopes under the overhang into an area not yet excavated. It is rich in shell fragments, flakes and lithic artifacts, and charcoal. It is worth noting that the shells include those of clams and giant chitons, species not found in the region today. Among the artifacts found are many large flakes, some retouched to form scrapers, along with flaked cobbles, cores, hammerstones, and abundant flaking debris. Charcoal samples from the lowest zone were dated between 8240 ± 160 and 8870 ± 60 RCYBP. Beneath the lowest stratigraphic zone is reddish brown loamy silt with coarse rubble, which overlies volcanic bedrock about 8 m (26¼ ft) below surface. Since charcoal fragments in this stratum had clearly intruded from above, no attempt was made to date this layer.

So far Abrigo de los Escorpiones has yielded about 800 artifacts (not counting unmodified lithic flakes still to be analyzed). Fine bifacially flaked specimens are rare; most artifacts are simple, chiefly large, heavy tools like flaked cobbles, hammerstones, and choppers.

Clearly the site has been used as a shellfish collecting station since at least the early Holocene, some 9000 years ago. The enormous shell deposits, however, obscure the vast interior of the rockshelter, where Gruhn and Bryan hope to find evidence of an even earlier occupation dating back to the Pleistocene.

They plan to resume excavating Abrigo de los Escorpiones this May and June. They're wiser now about the unique conditions at the coastal site. Fog commonly rolls in during the evening and lasts until mid morning, sometimes until noon. Condensation is a problem. "When we first went there," Gruhn remembers, "we stayed at a campground. In the morning tents, sleeping bags, everything would be soaked. You need a permanent shelter if you plan to be there for an extended period." Now they rent a house a few miles from the site.

They'll travel in a Chevy pickup. The Land Rover is in their garage, "not exactly in running condition," Gruhn admits. They just can't bring themselves to part with it. It's an old friend, like a faithful draft horse past its working years they won't send to the glue factory.

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