by Dennis Stanford and Bruce Bradley
For half a century, archaeologists have assumed that ancestors of the Clovis people — long considered the first Americans — crossed the Bering Land Bridge from northeast Asia some 12,000 radiocarbon years ago (14,000 calendar years BP), then spread southward across the continent.
Solutrean seafarers may have followed the edge of an icesheet that covered the North Atlantic during the last Ice Age to reach the coast of North America. Years of research in eastern Asia and Alaska have produced little evidence of any historical or technological connection between the Asian Paleolithic (Stone Age) and Clovis peoples. Also, the southeastern United States has produced more Clovis sites than the West, and a few radiocarbon dates suggest some of them may predate those in the western states. If correct, that hardly fits the notion that Clovis technology originated in northeast Asia or Alaska.
Over the years, various scholars have noted similarities between Clovis projectile points and “Solutrean” points, the product of a Paleolithic culture on the north coast of Spain between 22,000 and 16,500 years ago. Little credence has been given to suggestions of a direct connection between these technologies because of the 4,500-year time gap between the last of Solutrean and the first of Clovis, and because of doubts that people of the Upper Paleolithic could navigate the Atlantic Ocean.
But indirect evidence for Paleolithic ocean travel has been mounting. Although no boats have been found, we now know that by at least 40,000 years ago, watercraft carried a founding population to Australia. By 28,000 years ago, flintknappers were collecting raw materials from islands far off the Japanese coast. And closer to Spain, Paleolithic peoples inhabited some of the Mediterranean islands at least 14,000 years ago.
Solutrean peoples could have used this knowledge of watercraft to travel and exploit marine resources, which would have been especially important during the last glacial maximum, about 18,000 years ago, when most of Europe was covered with ice and competition for diminishing land resources must have been intense. Given these facts, we believe the hypothesis of a western Old World ancestry for Clovis should be reconsidered.
To determine whether the idea was worth additional study, we examined archaeological collections in Spain, France, and Portugal, looking for technological affinities between the European Upper Paleolithic and Clovis. Our cursory examination revealed an amazing correspondence between Solutrean and Clovis; in fact, Solutrean has more in common with Clovis than with Paleolithic technologies that followed it in Europe.
Solutrean and Clovis flintknappers used nearly identical stoneworking technologies. We observed a high degree of correspondence between stone and bone tools, as well as engraved limestone tablets, and caching of extra large bifaces and other tool stock. The Solutrean toolkit is, with a few exceptions, nearly identical to that of Clovis. Although some of the Solutrean concave-base projectile points are heavily thinned, none that we saw exhibited a well-developed Clovis-style flute. Clovis assemblages lack shouldered points and the Solutrean laurel-leaf knife.
A Solutrean origin for the Clovis culture seems a more parsimonious explanation of the evidence than an Asian ancestry. Certainly, if Solutrean industries were found in Siberia, no one would question their historical relationship with Clovis.
The ultimate test of this hypothesis may be found in genetic research on ancient human remains. Michael Brown and colleagues reported in 1998 that mitochrondrial-DNA haplogroup X (a genetic marker of population groups) is found in low frequencies in both European and Native American populations, but not among Asians. This indicated to them that some of the American founders may have come from Europe between 36,000 and 12,000 years ago.
Regardless of whether a Solutrean-Clovis link is eventually proven, exploring this hypothesis should increase our understanding of the development of technological innovations and broaden our knowledge of early peoples of the New World.
DENNIS STANFORD is Chairman of the Anthropology Department at the National Museum of Natural History, Smithsonian Institution.
BRUCE BRADLEY is President of Primitive Tech Enterprises, Inc., in Cortez, Colorado, and Adjunct Professor at Augustana College in Sioux Falls, South Dakota.
by D. Gentry Steele
Early American skulls don’t fit neatly into any theoretical box. The skeletal remains of the earliest-known Americans tell a story that is far more complex than previously thought, and it is a story that is still being interpreted.
But statistical analyses of measurements of ancient skulls (10,000 to 9,000 radiocarbon years ago, or 11,350-10,185 calendar years) and more recent Native Americans show that Paleoindians display differences from current American Indians and from modern populations of northeast Asia, the region typically cited as Native Americans’ ancestral homeland.
Specifically, the early skulls consistently have longer, narrower faces; longer, narrower braincases; a more projecting, mid-facial region; and cheekbones that slope to the rear.
Paleoindian cranio-facial features more closely resemble central and southern Asians, Polynesians, Australians, and some European samples than do most current American Indians. Walter Neves’ study of South American Paleoindian skulls found similar degrees of distinctiveness from recent populations in North and South America. He notes structural similarities of South American Paleoindians to Australoasian groups.
It should also be noted that American Indian populations across the Americas show at least as much cranio-facial variation as populations of other continents, based on W.W. Howells’ database of cranial measurements from populations throughout the world. Native Americans are, therefore, not so similar that colonization of the New World must have been a very recent event or have involved a single population.
My colleagues, especially Joseph Powell of the University of New Mexico, and I have been exploring this issue for over a decade. Our results are consistent, but limited by the paucity of very early remains. By 1994, fewer than 25 individuals could be considered at least 8,500 years old (9,509 cal BP), and only four skulls (from two males and two females) were complete enough to permit comparisons of more than one or two traits.
The sample improved recently with two virtually complete male skeletons, both from Nevada — Spirit Lake and Wizards Beach — and dated to about 9,200 years ago (10,335 cal BP).
To recognize and confirm the distinctiveness of the earliest-known human populations, we have applied an assortment of statistical analyses on various combinations of data from these samples and compared them with modern and prehistoric populations around the world.
The question now becomes this: What caused this distinctive cranio-facial pattern among Paleoindians, and why does it differ from modern Native Americans?
The most common explanation is gene flow: Current Native Americans physically resemble their geographically close northeast Asian neighbors because they are descended from them, while earlier American populations, with other ancestors, were absorbed or displaced. This process could have involved a recent population expanding out of northeast Asia, replacing some existing populations and pushing others into less-productive environments and genetic obscurity.
Another gene-flow model suggests a longer, less-intensive process: The variation in today’s Native Americans could result from mixing genes of a founding population with, in local populations, varying amounts of genes from later colonizers.
The original founding population for Paleoindians has been proposed by various researchers, based on physical/genetic characteristics, as early Asian (sometimes referred to as Protoasian or Protomongoloid), southern Asian (similar to the Jomon, an early population of Japan), Australoasian (most notably for South American Paleoindians), and European.
The principal limitation of the gene-flow model is its beguiling simplicity. By relying exclusively on this as the complete explanation of the differences between current Native Americans and the early North American remains, we ignore potentially powerful forces such as genetic drift (the random changes that alter a group’s gene frequencies over generations) and natural selection acting on populations as they adapt to local environments. Both processes, after all, have had thousands of years to work on the first Americans. At this stage, none of these three forces — gene flow, genetic drift, and natural selection — can be ruled out as a cause of the differences between early Paleoindians and later Native Americans.
The weight of the evidence, however, suggests the difference between early American populations and those of more recent times reflects a strong component of gene flow, from either small but rather constant trickles or waves of immigrants, or a short but expansive colonizing event.
Identifying the founding population of Paleoindians is much more difficult because the features that distinguish Paleoindians from more recent Native Americans are shared, at least in part, with a number of populations from the Old World, particularly those of its eastern margins.
Current data are not robust enough to identify precise ancestors of the earliest known colonizers of the New World. But the weight of the cranio-facial evidence clearly indicates we can no longer assume recent Northeast Asians were the first colonizers. I suspect the first colonizers will prove to be populations from southern or central Asia, such as the Jomon of Japan, although the evidence is as equivocal for this as for other views.
More importantly, we must recognize that in the biological world, processes and events are far more complex than our intentionally simplified models. For the peopling of the Americas then, the challenge we face in the future is to develop ways to verify that multiple forces are at work in a population and to tease out the role each plays in the process.
D. GENTRY STEELE is a Professor in the Anthropology Department at Texas A&M University and serves as Faculty Advisor to Texas A&M University Press.