Re: Native Americans (was: Out of Africa, Not Once But Twice)

On Mar 20, 10:01 am, g-hor...@xxxxxxx (G Horvat) wrote:
On Thu, 20 Mar 2008 05:04:56 -0700 (PDT), Jack Linthicum

<jacklinthi...@xxxxxxxxxxxxx> wrote:

[...]

Which is why, of course, the characteristics recently outlined for the
people who populated the Americas no longer exist in Siberia, a place
they are considered to have come from.

There's more involved than loss of characteristics:

"Consistent with this hypothesis are the younger coalescent dates for
modern Siberian populations relative to modern New World populations
[15,35], which indicate that the New World migrants passed through
Siberia before other East Central Asian population(s) settled
permanently in this region at a later date." (Kitchen et al., 2008,
PLOS)

I think it's time for a reassessment of what we really know.

Gisele

You have to define your terms. Here is a 12 year old statement from
Archaeology that is probably as true today as it was then. But there
are those who would argue that much has happened in the discipline of
archaeology and yet the overall and individual pictures are not clear.

The Great DNA Hunt Volume 49 Number 5, September/October 1996
by Tabitha M. Powledge and Mark Rose

Genetic archaeology zooms in on the origins of modern humans.

[image] (Illustration by Carlyn Iverson) [LARGER IMAGE]

DNA can be used to understand the evolution of modern humans, trace
migrations of people, identify individuals, and determine the origins
of domestic plants and animals. DNA analysis, as one scholar put it,
is "the greatest archaeological excavation of all time." Because
ancient DNA molecules are normally so few and fragmented, and
preserved soft tissues so rare, scientists had little hope of finding
and analyzing it. But two breakthroughs have made this possible: the
polymerase chain reaction (PCR), a method for copying any fragment of
DNA, and the successful recovery of DNA from preserved hard tissues,
bones and teeth, that are durable and relatively abundant.

DNA analysis traced human ancestry back to an African "Eve," setting
off debate about how modern humans evolved. While there was general
agreement that Homo erectus dispersed from Africa across Asia between
1 and 2 million years ago, what happened next remained a question. The
"out-of-Africa" hypothesis contended that modern humans developed in
Africa and migrated from there recently, driving H. erectus into
extinction. Proponents of a "multiregional" hypothesis held that H.
erectus populations evolved into modern humans in many regions, and
that these groups later bred with each other and with groups that
emigrated from Africa. The Eve study examined mitochondrial DNA
(mtDNA), which is passed only by mothers to their offspring. The
researchers, Rebecca Cann, Mark Stoneking, and the late Allan Wilson,
estimated that the ancestor of all surviving mt DNA types lived
between 140,000 and 290,000 years ago. When did the migrations from
Africa take place? They dated the oldest cluster of mtDNA types with
no modern African representation to between 90,000 and 180,000 years
ago. These populations might have left Africa at about that time, but
the mtDNA data could not determine exactly when.

Geneticist Alan Templeton pointed out statistical and sampling flaws
in the study. Its results, he argued, were in part dictated by the
order in which the data were fed into the computer. Others questioned
the reliability of "molecular clocks" and the rate of mutation in the
human mtDNA used in calculating Eve's date. The genetic diversity of
African populations was confirmed by later studies and is now
generally accepted, but, according to Templeton, proponents of the out-
of-Africa hypothesis assumed that genetic diversity reflected only the
age of a population rather than population size. He contends that
Africa has greater genetic diversity because its prehistoric
population was probably larger than elsewhere. Recently John
Relethford and Henry Harpending have argued that differences in
ancient population size could mimic a recent African origin of modern
humans. The data reflect population dynamics, they say, and do not
support one model of modern human origins over another.

Scientists are also studying DNA from the Y chromosome, which is
passed only from father to son and is not recombined with the mother's
genes. Because changes in the Y chromosome are caused only by
mutations, as in mtDNA, it may be used as a clock. Assuming that all
living humans share a common male ancestor, it should be possible to
estimate when he lived. According to geneticist Robert Dorit, the
first modern human male lived some 270,000 years ago. The most recent
research on modern human origins, by John Armour, examined nuclear DNA
of populations from around the world. Armour and his colleagues
conclude that the evidence fits with the development of modern humans
in Africa and an emigration by a small number of them that became the
basis for non-African populations. These observations, they say, are
more difficult to reconcile with a multiregional model for the origin
of modern humans.

New DNA studies by Bryan Sykes have challeneged the leading theory
about the spread of agriculture into Europe. In 1984 Albert Ammerman
and geneticist Luigi Luca Cavalli-Sforza of Stanford University
proposed that it was people practicing agriculture who spread into
Europe, rather than the idea of agriculture. They argued that
agricultural productivity led to population growth, and that, as the
population grew, early farmers gradually moved into new land inhabited
by fewer hunter-gatherers. Thus the practitioners of agriculture
spread from Anatolia, beginning about 7000 B.C., to Greece and across
all of Europe, ending in Britain and Scandinavia about 4000 B.C. Using
mtDNA analysis, Sykes claims that the ancestors of most modern
Europeans arrived at least 20,000 years ago, long before the supposed
arrival of Neolithic farmers. In analyzing mtDNA from more than 800
modern Europeans, Sykes and his colleagues identified at least five
main groups. Four of the five groups date to well before the last
glacial peak, with ages ranging from 35,000 to 25,000 years ago. The
fifth group is much younger in Europe (6,000 to 10,000 years ago) and
has clear affinities to Near Eastern mtDNA. Sykes and his colleagues
accept this as the genetic echo of the spread of agriculture, but note
that it is fairly weak. They conclude that, far from being overwhelmed
by incoming farmers, the indigenous hunter-gatherer population
remained intact and learned how to farm.

Documentation of the early presence of Caucasian people in
northwestern China, and information about their affinities with either
modern European or Indo-Iranian populations, could contribute to the
debate about the spread of Indo-European languages. Chinese and Uyghur
archaeologists have been excavating naturally mummified bodies there
since the 1970s. Paolo Francalacci of the University of Sássari,
Sardinia, took samples from several of the bodies, dated to 3,200
years ago DNA analysis for these mummies suggest a possible European
origin, although further research is needed to identify them more
precisely. As part of a larger project, Chinese geneticist Du Ruofu
has been collected samples of mtDNA from modern Tarim Basin
populations. Comparison will determine how much of the ancient genetic
composition survives.

Most scholars believe that people from the Asian continent came to the
Japanese archipelago in two migrations. An early wave brought the
Jomon culture--hunter-gatherers who made pottery--to Japan more than
10,000 years ago. A second migration began about 2,300 years ago, when
the Yayoi people, entering from the Korean Peninsula, brought weaving,
metalworking, and rice culture to Japan. First appearing on the
southwestern island of Kyushu, by ca. A.D. 300 Yayoi culture had
spread throughout most of Japan, altering all local cultures south of
Hokkaido, the northernmost island. Michael F. Hammer and Satoshi Horai
are examining the extent to which the Jomon did or did not contribute
genetically to the modern Japanese. Current hypotheses can be
classified as replacement, hybridization, or transformation. In the
first, Yayoi immigrants replaced the Jomon people. Hybridization
theories claim that modern Japanese are descended from both groups, in
which case they should have genes deriving from both the Jomon and
Yayoi people. Transformation theories posit that modern Japanese
people gradually evolved from the Jomon. Hammer and Horai, based on
their study of the Y chromosome, conclude that hybridization, a mixing
of Jomon and Yayoi stocks, is the most likely explanation for the
origin of modern Japanese.

Nonhuman DNA has great potential for shedding light on cultural
practices. Recent work by Daniel Bradley is a case in point. Before
now it was assumed that cattle were first domesticated in the Near
East. African, European, and Indian cattle were all thought to be
descended from a domesticated Near Eastern progenitor, and to have
developed into characteristic breeds afterward. Bradley and his
colleagues have determined that Indian cattle broke off from an
ancestral lineage between 117,000 and 275,000 years ago. The lineage
split again about 22,000 to 26,000 years ago into groups that gave
rise to modern African and European cattle. These are startling
results because cattle in the Near East were not domesticated until
about 9,000 years ago, and cattle in India and Africa were genetically
distinct before then. The latter two could not possibly be descended
from domesticated Near Eastern cattle, as was thought, but must have
been domesticated independently.

Geneticist Terence A. Brown and his colleagues have devised a way to
identify types of wheat using DNA analysis. This will make it possible
to determine whether primitive wheats or modern varieties were grown
at a site. The higher productivity of modern varieties means that a
larger population could be supported, and fewer people had to be
involved in farming. This may have been a factor that sustained the
rise of classical civilizations. Brown also hopes to use similarities
and differences in wheat DNA to investigate the relationships between
Celts and Romans in Britain. Did the Romans bring their own wheat, or
did they rely on indigenous agriculture to support the Roman
community?

This is the first in a two-part series on genetic archaeology. Our
second installment, in the November/December issue, focuses on DNA
investigations that challenge the most widely accepted model of how
the New World was colonized.
http://www.archaeology.org/9609/abstracts/dna.html

The Great DNA Hunt, Part II Volume 49 Number 6, November/December
1996
by Tabitha Powledge and Mark Rose

Colonizing the Americas

[image] Recent theories held that Native Americans colonized the New
World in three migrations. New DNA studies suggest there was only one
migration that lasted perhaps thousands of years. Key Paleoindian
sites are indicated on map along with ice sheets, glaciers, and now
submerged lands during the last glaciation.(Lynda D'Amico) [LARGER
IMAGE, 36K]

The latest DNA investigations are challenging a widely accepted model
of how the New World was colonized. While scholars agree that people
entered the Americas via a land bridge linking Siberia and Alaska,
there has been debate on when they crossed and whether they came at
one time or in several waves. An initial consensus held that
Paleoindians came to the New World about 14,000 years ago and that
most Native Americans are descendants of these people, with the
exception of Eskimo-Aleuts, who arrived much later. In the mid-1980s a
revolutionary model claimed three distinct migrations, including the
Eskimo-Aleuts, based on linguistics, dental morphology, and genetic
markers such as blood types. Studies of DNA in Native American and
Siberian populations in the early 1990s supported this model, but the
latest DNA analyses indicate the single Paleoindian migration might be
right after all.

Not all New World DNA studies focus on the colonization of the
Americas. Many investigations deal with individual sites and the
development of cultures in particular regions. Here the questions are
about such matters as social status, diet, and gender roles.

The use of DNA analysis to answer archaeological questions is little
more than a decade old, and has vast potential. Archaeology will
change with the development of this new discipline. Anne Stone of
Pennsylvania State University notes that DNA analysis in archaeology
"is probably going to remain a small, specialized field because of the
slow, frustrating, and fairly expensive nature of the work," but she
adds that "ancient DNA is very exciting because we have the
opportunity to address questions about human population history
ranging from local questions, such as whether a group of people in a
tomb are related, to larger questions, such as the history of the
migration into the New World."
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© 1996 by the Archaeological Institute of America
www.archaeology.org/9611/abstracts/dna.html

and Part I

.