Besides inventing the dog, the Upper Paleolithic people of East Asia made another historical contribution: they discovered and colonized the two major continents of North and South America. Genetic comparison of present day Siberians and American Indians may at last be bringing some resolution to two long running academic disputes about the settling of America. One is linguistic, the other archaeological.
More than 600 languages are spoken by American Indians and they are so different from each other that most linguists have regarded them as being derived from several different language stocks. In many disciplines there are lumpers, who see patterns and commonalities, and splitters, whose preference is to define differences. In historical linguistics, the splitters have the majority. A leading, and generally lonely, lumper is the late Joseph Greenberg of Stanford, a maverick with a fundamentally different view on how to establish the relationship among groups of languages.
In 1987 Greenberg caused more than usual distress among his fellow linguists when he announced his finding that all American languages fell into just three major families. There was Eskimo-Aleut, a group of 10 languages spoken by Eskimos and the inhabitants of the Aleutian islands off Alaska. There was Na-Dene, a family of 32 languages spoken only in North America, by the
Apache, the Navajo and tribes in Canada and Alaska. And finally there was Amerind, a group to which in his view all 583 other languages of North and South America belonged.
Greenberg well understood that the specialists in various Indian languages would not embrace the idea that their beloved tongues were all splinters off the same block. "I am therefore well aware that what is attempted in this work runs against the current trends in Amerindian work and will be received in certain quarters with something akin to outrage," he wrote. "Given the investment in time and energy that has led to results different from mine, such a reaction is 135
wholly understandable."_The implication that his opponents' ardor was more substantial than their acumen reflects the general state of relations between Greenberg and his critics.
Greenberg broadened his linguistic classification into a sweeping and attractively elegant hypothesis. He suggested that the three language groups he had defined represented three separate waves of migration into the Americas from Siberia. There were independent reasons, he noted, from study of teeth and of immunology, for assuming there had been three distinct waves of immigrants. As might be expected, the three migrations are packed into the Americas in order of arrival. The Amerind-speakers, who reach to the tip of South America, were clearly the first. Greenberg suggested they entered America from Siberia about 12,000 years ago and he linked their arrival with the appearance of what archaeologists call the Clovis culture, the earliest indisputable evidence of human presence in the Americas. The Clovis people lived on the Great Plains and hunted mammoth and bison from 11,500 until about 11,000 years ago. At this date the mammoth and several other larger American species became extinct, a customary indicator of human arrival, although in this instance the ending of the Pleistocene ice age may also have been a factor.
Several thousand years after the Amerind migration came the Na-Dene speakers of northwest North America, Greenberg supposed, and last to arrive were the Eskimo-Aleut of the circum-Arctic.
The relatively recent date adduced by Greenberg for the first entry to the Americas supported his position that it should be possible still to see links between the various Amerind languages. But archaeologists have long been seriously divided over the question of first entry. No human remains older than those of the Clovis culture have yet been discovered, but there are hints of an earlier presence, notably at the Monte Verde site in southern Chile. One layer of apparent artifacts, mostly plant remains and wooden objects possibly associated with tents, has yielded radiocarbon dates of 12,500 years ago, while a deeper and more doubtful layer has produced dates of 33,000 years ago. After initial rejection and long debate, archaeologists have finally accepted the 12,500-year layer, though not the older stratum, as evidence of a pre-Clovis presence, according to a recent review.^ This gives a date slightly before
Clovis, but still leaves the impression, at least on archaeological grounds, that the two continents were empty of people prior to 14,000 years or so. When the geneticists first arrived on this particular academic battle-ground, they generally favored the idea of a few migrations, though not necessarily just three. But mitochondrial DNA, the genetic element they were first able to analyze, pointed to much earlier dates for the colonization of the Americas, lending preliminary support to the archaeologists who favored seriously pre-Clovis dates of settlement such as 30,000 years ago. There are five groups of mitochondrial DNA lineages in the Americas, the groups known as A, B, C and D, as well as the small lineage X, which has a special history. A, C and D are also found in northern latitudes of Asia and in northeastern Siberia but B has a different distribution, being found in southeastern Siberia. That led Douglas Wallace, of the University of California at Irvine, to suggest that the first entry into the Americas occurred 34,000 years ago and consisted of people carrying lineages A, C and D migrating from Beringia. There was then a second migration, 16,000 to 13,000 years ago, according to mitochondrial DNA evidence, that brought lineage groups B and X to the Americas. The Eskimos and Na-Dene speakers appeared on the scene
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