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Languages, Teeth, DNA, Boats, Beringia, and Controversy:
An Examination of the Debate Over Various Aspects of the Initial Peopling of the Americas
Ever since the arrival of Europeans on the North American continent people have been
curious about the origins of the Native Americans. Over the past few centuries, and especially in
the past one hundred or so years with the advent of professional archeology, a good many
questions surrounding the origins of these people have been asked and answered. However, even
as older questions, such as whether the Clovis settlement represents the earliest group of Native
Americans, appear to be answered, even more questions arrive. While today it is generally
accepted that the Native Americans are descended from people who originally came from Asia, a
number of questions over the specifics of their ancestors have arisen. Questions such as whether
there were multiple migrations of people, whether such migrations were made up of different
populations and gave rise to different groups of Indians, where exactly in Asia these people came
from, whether they crossed by land or water, and even whether the first inhabitants of the
Americas are the same people whose descendents inhabited the continents in 1492, are
continually posited. To try to answer such questions, archeologists today make use of various
types of evidence and some of the very latest in scientific techniques. Linguistic evidence may
agree with dental evidence yet come into conflict with the findings of researches that examine
mitochondrial DNA. As this controversy continues, new studies are constantly being done, old
research reexamined, and paper after paper is presented, published, and argued about.
One of the major bones of contention today is over the exact number of migrations that
took place from Asia. A related question, and one which has often been examined in an attempt
to answer the migration question, is how many distinct populations the Native Americans can be
grouped into. A variety of approaches have been taken in order to try to answer these questions,
including examinations of linguistic, dental, and genetic evidence. Regardless of how many
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migrations various archeologists believe have taken place, they have often assumed that all of
these people simply crossed the Bering land bridge, or Beringia, during the last ice age, and then
moved down into continental North America when the ice sheets receded. This model of New
World immigration was generally accepted, and is still accepted by many, in part because it
worked well with certain other theories about paleoindians, such as that of Clovis. However,
with the mounting evidence against Clovis as the earliest spot of occupation, and with mounting
evidence that areas of the Pacific Coast may have been the earliest places of settlement,
proposals for an initial migration by water instead of land have been advanced. This
controversy, though less written about so far, is also an important one that must be examined and
resolved in order for a complete model of the initial peopling of the Americas to ever be
constructed and agreed upon.
A landmark in the controversy over the number of migrations, as well as an excellent
case study in the use of a variety of scientific disciplines to answer archeological questions, is a
1986 article by Joseph Greenberg, Christy Turner, and Stephen Zegura entitled “The Settlement
of the Americas: A Comparison of the Linguistic, Dental, and Genetic Evidence.” This article
set forth the so-called Greenberg Hypothesis, which states that three separate lines of evidence
all point to the conclusion that the Americas were initially settled by three migratory waves,
which developed into three distinct groups, namely the Amerind, Na-Dene, and Aleut-Eskimo.
The article itself briefly outlines the ways in which the evidences were used to create and support
a three-migration model. Attached to the article are a number of comments from various
scholars which question and even attack the hypothesis as well as a reply from the three authors.
Together the article, commentary, and reply are an excellent illustration of the debate that has
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raged on in recent years over this and other questions about the initial peopling of the Americas,
as well as demonstrating the controversy over the Greenberg Hypothesis itself.
The Greenberg Hypothesis, while using genetics and dental data as support, rests largely
upon the linguistic evidence. Greenberg, the linguist of the group, begins his argument by citing
his own research on the classification of indigenous American languages, which he says leads to
the unmistakable conclusion that there are three and only three linguistic groups in the Americas.
He argues that “the oldest is probably Amerind, since it centers farther to the south and shows
greater internal division”. Additionally, he cites less differentiation in the north as evidence for a
“relatively rapid spread” from that area. The article argues that the Na-Dene grouping is the next
oldest since it “has deeper internal divisions and is geographically less peripheral than AleutEskimo,” which is viewed as the last group which arose from a third, later migration. Greenberg
subsequently restates his thesis and argues that the language groups are too different to come
from a single linguistic stock.
The dental evidence, Turner’s contribution, is the next to be presented, and is utilized so
as to lend support to the hypothesis which was constructed on linguistic grounds. Turner begins
by presenting four observations, the last of which suggests that the Na-Dene, Aleut-Eskimos, and
“all other Indians form three New World dental clusters.” From this and other evidence he
creates a dental hypothesis that, like the linguistic one, “envisions three distinct late Pleistocene
migrations from Siberia.” Turner also suggests that since dental variation is greater in the North
than in the South, that population movement “proceeded from Alaska southward.” To his credit
then, but not so now, Turner than argues that his evidence “corresponds well with the widely
held view that the first Americans were the Clovis culture”, basing this statement on the
agreement on his own dental divergence rates and mainstream archeological evidence. Turner
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also discusses the ways in which his dental evidence agrees with Greenberg’s linguistic
evidence. He states that there is “a good fit between Greenberg’s Macro-Indian (Amerind) and
Aleut-Eskimo linguistic divisions and the dental clusters” but that there is less agreement
between the two types of evidence when it comes to the Na-Dene. He then proceeds to offer
some possible explanations for this disagreement, as well as restating that regardless of it, the
dental evidence also points to three separate migrations.
Zegura next discusses the genetic evidence, based upon the examination of mitochondrial
DNA, as it relates to the Greenberg hypothesis. It is stated that the three authors “view the
interpretation of the genetic data as secondary support for the primary inferences based upon
linguistic and dental data.” While the lack of development of DNA technology in the mid
nineteen eighties is one reason for this qualifier, another is that the genetic evidence does not
lend strong support to the Greenberg Hypothesis. The article itself discusses other possible
interpretations of the genetic evidence and even states that “from a genetic perspective the
hypothesis of three separate migrations leading to a tripartite division of modern Native
Americans is still without strong confirmation.” Thus, while the linguistic and dental evidence,
despite some minor disagreement, tend to lend strong support to the Greenberg Hypothesis, the
genetic evidence presented in the article is significantly weaker.
The Greenberg Hypothesis created controversy immediately after it was published. A
number of commentaries published with the article question the their evidence as well as their
interpretation of that evidence. Lyle Campbell argues that “Amerind is discounted by nearly all
specialists” and that the dental and genetic evidence used to support the linguistic hypothesis are
unconvincing and open to alternate interpretation. He views the entire hypothesis as a sort of
house of cards, and even chastises Greenberg for his use Amerind classifications. James Fox
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grants the three groups, but points out that Greenberg use the absence of variation while Turner
uses large variation in the North in order to support views of rapid migration. W. S. Laughlin
argues that, contrary to the conclusions of Greenberg, Turner, and Zegura the “differences
between American populations are not large enough to postulate more than one migration.”
Szathmary questions of the interpretation of the genetic evidence, while Weiss and Woolford are
concerned with the validity of some of the methods used in the study, as well as why the dental
data, which is ultimately based upon genetics, is weighed more heavily than the DNA evidence.
The authors of the article responded to these criticisms, accepting some as valid, while flatly
disagreeing with others. The pointed out that nearly all the commentators agreed on one to three
waves being necessary to explain the variation and then went on to state that Turner had
“evaluated models of one to four migrations” but had come to the conclusion that only the
“three-wave scenario stands up” to scrutiny. Despite the immediate criticisms the authors stuck
by their hypothesis, but the controversy present within the debate over one article was only an
indication of what was to come
A number of more recent articles, many of them making use of more modern genetic and
other biological technologies and the evidence derived from the use of such techniques, have
challenged the Greenberg Hypothesis. A 1992 article by Steele and Powell concluded that “the
number of founding populations [could not] be discerned” from an examination of fossil
remains. A 1996 article by Ann Gibbons goes much further. She presents genetic evidence
which creates a model whereby the ancestors of Native Americans migrated to North America in
either one or two waves, but not three, thus contradicting the Greenberg Hypothesis. The article
spends a great deal of time discussing the merits and the legacy of the Greenberg Hypothesis,
outlining the history of controversy surrounding it and stating that genetic evidence of the early
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nineties had lent further support to it. The new genetic evidence presented in the article, based
on new DNA findings and heightened technology, undercuts the Greenberg model, however. In
the article geneticist Ryk Ward argues that the genetic evidence illustrates that “there isn’t a
relationship between genetic signatures of migrations and language" which further calls into
question the Greenberg Hypothesis. According to geneticist D. Andrew Merriweather, who also
appears in the article, the presence of certain genetic markers in all three of the proposed
linguistic groups “makes it unlikely that the groups’ ancestors came in different migrations.” A
new model put forth in this article proposes that one population gave rise to all three linguistic
groups. This model argues that the ancestors of the Amerinds moved south first, while the
ancestors of the Na-Dene and Eskimo-Aleuts stayed back and lost some of their genetic diversity
due to population decreases. Later these groups rebounded, spread out, and gave rise to the
linguistic groups of today. This model has alternately been called both a one or two migration
model but is called by its proponents one of a single migration followed by “a re-expansion.”
The Gibbons article also points out that linguists, stemming back all the way to Campbell, have
questioned the validity of the Amerind grouping. Thus in 1996, this new model, based upon
genetic evidence, was only one of a series of challenges to the Greenberg Hypothesis.
More recent genetic evidence also supports a single migration hypothesis. A 1997 article
by Bonatto and Salzano utilizes mitochondrial DNA evidence as well as geologic data to propose
a model similar to that which appears in the Gibbons article. In this model the Amerind groups
arose out of the larger Native American population occupying Beringia over 20,000 years ago.
Between 20,000, and 14,000 years ago part of the population was isolated in the South by the
collapse of the ice-free corridor they had used to move southward. The groups that remained
gave rise to the Na-Dene and Aleut-Eskimo. Recent articles by Mark Stoneking and others have
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also proposed a single migration model. A February 1998 article authored in part by Stoneking
presented three genetic groups for the Americas which were divided largely by geography, rather
than by linguistic or dental variation. This article argues that for one of two interpretations
which include the provision that there was only one founding population. Either the various
genetic differences among groups of Indians arose due to “a single migration to the New World
followed by partial isolation and genetic drift” or “instead of a single migration wave, several
migration waves from the same source population took place.” In another 1997 article, coauthored with Anne Stone, Stoneking again reasserts that “a single migration of a population
with significant mtDNA diversity” is suggested by the mitochondrial DNA evidence, while the
Greenberg Hypothesis of three migrations has no such support. A 1999 article by Stuart Fiedal
argues that the sum of the genetic evidence goes against the Greenberg Hypothesis while stating
that new, earlier dates for the initial peopling of the Americas mean that, contrary to Greenberg’s
earlier conclusions, the linguistic differences between the Amerind, Na-Dene, and Aleut-Eskimo
groups need not indicate three separate migrations.
Another theory concerning initial peopling of the America’s was put forth not long after
the Greenberg Hypothesis, though it is not necessarily in conflict with the earlier theory. In 1988
Ruth Gruhn, put forth evidence supporting a model whereby the initial migration to the Americas
would have taken place by sea rather than by land over Beringia. Like Greenberg, Gruhn uses
largely linguistic data. She cites research by Richard Rogers, which suggested that the great
linguistic diversity found in the Pacific Coast area of North America indicates that the peopling
of the Americas took followed “an initial coastal entry route, and only secondary occupation of
the interior.” Gruhn states that her scenario, in which the first settlers of the Americas moved
south along the Pacific coast, is “hypothesized on the basis of the linguistic evidence,” but she
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also uses evidence of early coastal area occupation, such as Monte Verde, to support her model.
She points out that, with the Clovis model faltering, her hypothesis could be used to explain how
people had arrived in the Americas at a time when the ice sheets were still blocking land entry.
In the time since this model was proposed it has received both some support and some
opposition.
One example of the opposition that this model has provoked comes from a 1996 review
by Robert Kelly that appeared in American Antiquity of a volume of essays on various aspects of
the peopling of the Americas. Kelley’s criticisms of Gruhn specifically center around her
interpretation of some data and her “premise that geographical areas occupied longer will show
greater language diversification.” He points out that those who use linguistic data tend to ignore
the fact that “language is behavior and behavior is adaptive,” and that linguistic change over time
may thus not be a good indicator of when certain things, such as migrations, took place. He also
points out that Goddard and Campbell do not feel that “linguistic diversity on the coast
necessarily indicates” longer term occupation and that Gruhn's demonstration of the possibility
of a seaward migration “in now way proves the claim.” A 1996 article by Carles Fox does lend
support to Gruhn’s model, however. Along with supporting a multiple migration model, this
article also postulates that “a coastal route along the Pacific Ocean” could have given rise to
certain tribes, while others may have arrived by land. However, it should be noted that nearly all
of the migration models which were presented earlier, whether agreeing with or disputing the
Greenberg Hypothesis, tend to take a land based initial migration forgranted.
Having presented the evidence and arguments on both sides of these controversies, the
question of what to conclude comes to the fore. What model, or combination of models, of the
initial peopling of the Americas can be supported by the greater weight of the available
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evidence? In short, what, if any, conclusions can be reached about the number of migrations that
it took to populate the New World and whether these any of these migrations could have been by
boat rather than across Beringia and through the ice free corridor into central North America? I
will turn first to the Greenberg Hypothesis and the controversy over the number of migrations
and then quickly attempt to draw a conclusion about Ruth Gruhn’s ideas concerning a possible
water based initial migration.
What, if any, determination can we make about the validity of the Greenberg Hypothesis,
especially in light what appear to be waves of new and contradictory evidence coming out of
genetics laboratories? In order to make a fair assessment of Greenberg it is necessary to boil
down the controversy as much as possible. In essence, the debate is over there where three
migrations, which were the ancestors of three distinct populations, or fewer than that. It must be
remembered that Greenberg did not base his theory on nothing, and while others have and will
likely continue to dispute some of his linguistic classifications, it must be remembered that he is
an eminent scholar in his field and that, to him, the evidence points to a three wave migration
scenario. Furthermore, it should be noted that Turner’s data, while not agreeing exactly with
Greenberg on all points, also points to three distinct populations and, by extension, three separate
migrations. So the Greenberg Hypothesis was based on conclusions from scholars in more than
one discipline. In addition, those who disputed Greenberg’s linguistic classification (and his
theory) originally did so on the grounds that Amerind was too diverse to be from one migration,
while the arguments against his theory today are in favor of even fewer migrations. Therefore, if
one is to dispute this theory today, one really ought to do so on exclusively genetic grounds.
And, indeed, this is where most recent opposition has come from. While most of this evidence
does seem to go against the Greenberg Hypothesis, it is open to interpretation and to such
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questions as whether the fact that all of Greenberg’s populations seem genetically related can
actually be used to prove that they all came over in one migration. Questions of on which
continent such divergence may have taken place will hopefully be resolved in the near future,
especially with the opening of Siberia to scientific study. Yet even after such study it may still
prove impossible to answer this vexing question to everyone’s satisfaction. I believe, though the
genetic evidence may push some to do so, that Greenberg’s model cannot be thrown out at
present. However, as an absolute answer to the question of how many migrations there were to
the Americas, the hypothesis seems to be losing ground and may eventually have to be
abandoned.
If anything it is even tougher to make a determination on Ruth Gruhn’s theory concerning
initial migration by water. While there are arguments on both sides of this issue, the evidence
used to back up such arguments is even less tangible than that used in the debate over
Greenberg’s theory. While it has been pointed out that demonstrating the possibility of water
travel does not prove it, there is much to be said simply for her showing that such a scenario
could have occurred. As always, more research should be done, and one hopes that the
controversy is interesting enough to provoke such research. It must be remembered that this
model goes against one of the longest held, and longest taken forgranted, views on the peopling
of the Americas, and is bound to meet much opposition. Still, with the date for the initial arrival
of migrants thrown back into question, and especially with such sites as Monte Verde indicating
very early coastal settlement, I believe that her theory must be taken seriously, and must be
considered as any new model of the initial peopling of the Americas is constructed. Indeed, with
the fall of the Clovis model, old theories are being questioned, new models proposed, more
research done, all with the hope of someday finding an answer to a 500 year old question.
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