This guest post is by Roy King, who is a professor of psychiatry at Stanford University and a research colleague of Stanford geneticist and 23andMe scientific adviser Peter Underhill. Roy and Peter have been using genetics to trace the spread of agriculture from the Near East to Europe.
<img loading="lazy" decoding="async" src="https://blog-api.23andme.com/wp-content/uploads/2008/07/germanvineyard.jpg" alt="" title="germanvineyard" class="alignright size-full wp-image-564" width="350" height="260" srcset="https://blogcms.23andme.com/wp-content/uploads/2008/07/germanvineyard.jpg 350w, https://blogcms.23andme.com/wp-content/uploads/2008/07/germanvineyard-300x223.jpg 300w" sizes="auto, (max-width: 350px) 100vw, 350px" />
The question of how agriculture first arose and spread in Europe has perplexed archaeologists and geneticists alike for decades. Evidence for farming communities in Greece, Crete, the Balkans, Southern Italy, and Mediterranean France and Spain first appears in the archaeological record eight to nine thousand years ago with the appearance of domesticated wheat, barley, sheep, goats and cows, and a related culture featuring pottery and anthropomorphic figurines. Before this period, most of the indigenous people of Europe fished, hunted small game or foraged for their livelihood.
But how did farming get to Europe in the first place? We know that 2,000 years before agriculture hit Europe, just after the end of the Ice Age, people living in the Near East had already developed farming, with the domestication of wild species of grasses, goats and cattle likely beginning in the fertile river valleys in present-day northern Iraq, Syria and southeastern Turkey. Near Eastern farmers also settled in villages and produced pottery and ceramic human figurines similar to the ones later found across Mediterranean Europe.
So did the first farmers of the Near East hop into boats with their domesticated plants, animals and artistic motifs and colonize Mediterranean Europe? Or did native Europeans learn about farming through trade with the Near East and decide to adopt this agricultural economy too? 
 
Genetic studies are starting to provide answers to this enduring question. Not only do genetic studies of sheep, goats, cows and wheat demonstrate that the European varieties are subtypes of the species found in the Near East, but data from the human Y chromosome suggest that people currently living in Southern Europe are descended in large part (at least through the paternal line) from the Near East. This suggests, at least for the Mediterranean areas of Europe, that the most probable scenario is that Near Eastern farmers did actually move into Europe, bringing farming with them.
23andMe has a Y chromosome marker on its custom chip, rs34126399, which captures the spread of agriculture from the Near East to Europe. The G state at rs34126399 is found in most individuals carrying paternal haplogroup J2a, whose origin can ultimately be traced to Turkey 15,000 to 20,000 years ago. Southern Turkey is the likeliest source for the initial domestication of wheat.
<img loading="lazy" decoding="async" class="aligncenter size-medium wp-image-559" title="rs34126399" src="https://blog-api.23andme.com/wp-content/uploads/2008/07/rs34126399.png" alt="" width="222" height="172" />
In the millennia after its appearance in Turkey, rs34126399G then experienced a population growth and spread westward into the eastern Mediterranean and eastward into Mesopotamia, Iran and northern Egypt. The map to the right shows the present-day distribution of rs34126399G in Europe and the Middle East.
In addition to its high frequency in the Near East, rs34126399G is present in 10 to 25% of the population of southern Greece and Italy, Crete, Sicily, Bulgaria and Romania. The concentration is an indication of the early spread of farming to these regions, where the climate of wet winters and hot dry summers suited the varieties of winter wheat that were first domesticated.
Since the initial movement of people associated with the origins of agriculture nearly 10,000 years ago, there has been persistent contact and trade throughout the Mediterranean. Just think of the Mediterranean diet – rich in olive oil, goat cheese, and red wine – all of whose origins can be traced to these regions. One archaeologist described the Mediterranean Sea figuratively as a giant bathtub that for millennia has permitted easy seafaring transit from one area to another. The genetic evidence appears to support that analogy.

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23andMe Blog Team

The Origin of Farming in Europe: A View from the Y Chromosome

<img loading="lazy" decoding="async" width="290" height="400" class="right size-full wp-image-281" style="float: right;" title="jessejamessmall" src="https://blog-api.23andme.com/wp-content/uploads/2008/06/jessejamessmall.jpg" alt="" srcset="https://blogcms.23andme.com/wp-content/uploads/2008/06/jessejamessmall.jpg 290w, https://blogcms.23andme.com/wp-content/uploads/2008/06/jessejamessmall-218x300.jpg 218w" sizes="auto, (max-width: 290px) 100vw, 290px" />Jesse James

Editor&#8217;s note: This post has been corrected from the original, which gave the incorrect location of Jesse James&#8217; grave. 


One of the most engaging features of 23andMe’s Personal Genome Service is a customer’s ability to trace his or her genetic ancestry using the mitochondrial DNA and the Y-chromosome.
Once customers learn their own ancestry, the Genome Sharing feature allows them to see how they compare with friends and family.
However, the ancestry section of 23andMe also allows customers to see how they compare to well-known individuals. In the maternal and paternal ancestry features, customers can view the haplogroup assignments of such figures as Thomas Jefferson, Genghis Khan and Bono.
<h6>Am I Related to Someone Famous? Sort of.</h6>
But how can anyone know the ancestry of someone like Thomas Jefferson, who has been dead for a few hundred years, or Genghis Khan, who has been dead for close to a thousand?
It turns out there are several ways to find out these well-known figures’ ancestry. The most obvious: Celebrities can sign up for 23andMe’s Personal Genome Service, just like the rest of us! For example, Jimmy Buffett and Warren Buffett have been interested for years in finding out whether their shared surname was an indication of common genetic ancestry. Unfortunately, their genetic profiles show the two are not closely related.
<h6>
 Founding Fathers&#8217; Haplogroups</h6>

But what about people like Thomas Jefferson?
He is no 23andMe customer, but this does not mean that scientists cannot trace his ancestry by other means. Tracing the maternal or paternal ancestry of any deceased individual is usually done by one of two ways: either getting DNA from the physical remains of the individual, or getting DNA from direct descendants of a relevant lineage.
He is no 23andMe customer, but this does not mean that scientists cannot trace his ancestry by other means. Tracing the maternal or paternal ancestry of any deceased individual is usually done by one of two ways: either getting DNA from the physical remains of the individual, or getting DNA from direct descendants of a relevant lineage.
In the cases of Thomas Jefferson and Benjamin Franklin, scientists used DNA from direct descendants of their ancestors. For example, in 1998 scientists inferred Jefferson’s paternal ancestry by analyzing the Y-chromosome of direct descendants of Jefferson’s paternal uncle (Jefferson had no confirmed sons).
<h6>Marie Antoinette and other Royal Haplogroups</h6>
Likewise, in the case of historical royalty such as Tsar Nicholas II of Russia or Marie Antoinette of France, extensive and detailed royal pedigrees make finding direct descendants a breeze.
Likewise, in the case of historical royalty such as Tsar Nicholas II of Russia or Marie Antoinette of France, extensive and detailed royal pedigrees make finding direct descendants a breeze.
In the case of the infamous outlaw Jesse James, a more direct approach was used. It had been widely believed that after James died in 1882, his body was buried at Mt. Olivet Cemetery in Kearney, Missouri. In order to test this hypothesis, scientists exhumed the body, extracting a few teeth. They compared DNA from the teeth to that of the great-grandson and great great-grandson of James’ sister. Scientists found an exact match between the extracted teeth and James’ sister&#8217;s descendants, thus confirming that the body in Mt. Olivet Cemetery was most likely that of Jesse James and establishing his ancestry to boot.

<h6>
How about Genghis Khan?</h6>
He is listed in our famous people sidebar as being a member of Y-chromosome Haplogroup C. But we do not have any information on his direct descendants alive today, nor do we have any preserved remains of his body. However, scientists have examined the Y-chromosomes of many present-day inhabitants of Mongolia (the ancestral home of Genghis Khan).
In doing so, they have found that about 8% of Mongolian males share the exact same DNA pattern in a highly variable part of their Y-chromosomes. Further analysis has revealed that this particular Y-chromosome type, which falls into haplogroup C, originated about 1,000 years ago and that its dispersal across Central Asia corresponds to the boundaries of the Mongol Empire. Historians have long noted Khan’s prolific nature; he is rumored to have fathered more than 40 sons, with some of his descendants also fathering many sons of their own. So it&#8217;s a good bet that we&#8217;re seeing Genghis Khan&#8217;s legacy in the 8% of Mongolian males alive today who have identical Y-chromosome signatures.
There are a number of ways we can determine the haplogroups of well-known figures — both past and present — and displaying information about these individuals adds to the fun of understanding and comparing the genetic ancestry of ourselves, our friends and family, and the rich and famous (or infamous).
Explore the origins of your ancestry at <a href="https://www.23andme.com/dna-ancestry/">23andMe.com</a>.

Haplogroups of the Rich and Famous

Roy King is a clinical psychiatrist at Stanford University. He’s also a scholar who uses genetics and archaeology to figure out how agriculture spread through Anatolia and the Mediterranean region of Europe more than 10,000 years ago.
Now Roy has another genetic puzzle to consider — himself.
With the help of 23andMe, he can now see how his own family tree — which has African American, Native American and Ashkenazi Jewish branches — is reflected in his genome.
Roy recently sat down with some of 23andMe’s scientists to look at his Ancestry Painting. (You can watch video of his conversation with 23andMe’s Matt Crenson below.)


An element of our Personal Genome Service, Ancestry Painting examines the 22 bi-parentally inherited chromosomes one segment at a time and determines for each stretch whether it was most likely inherited from ancestors in Africa, Europe or Asia. Roy’s painting is one of the most colorful our scientists have ever seen — an intricate patchwork of blue, orange and green. The colors indicate which segments of Roy’s DNA he inherited from ancestors in Europe, Asia and Africa respectively.
Though the pattern may look random to the untrained eye, it actually reveals a wealth of information about Roy’s ancestry. It also confirms a lot of what he has discovered in researching his genealogy.

For example, Roy has found records indicating that two 19th-century ancestors on his mother’s side were Native American. The orange stretches in his Ancestry Painting support that account. Native Americans tend to have predominantly orange paintings, with a smattering of blue indicating their descent from Ice Age hunters who lived in Siberia, a part of Asia with some European genetic influence.
According to Roy’s family tree about one-quarter of his ancestry should trace to Europe, because his paternal grandfather was an Ashkenazi Jewish man from New York City.
His other three grandparents were African American.
So why does his Ancestry Painting indicate 51% European ancestry, rather than something closer to 25%?
The reason is that like most African Americans, Roy has some European ancestry from the pre-Civil War era. Roy’s genealogical research suggests, for example, that his great-grandmother may have been the daughter of a white man who raped his great-great-grandmother. Another of Roy’s great-great grandmothers came from New Orleans, where research has shown that the African Americans average about 20% European ancestry.
For an illustration of how a person’s Ancestry Painting and family tree match up, take a look at this illustration of Roy’s pedigree.
Instead of labeling each oval (indicating a female) or square (male) with names and birthdates, we’ve given them colors. Green indicates a person who would typically be considered African American, blue a person of European descent and orange a Native American.
There appears to be more green in Roy’s family tree compared to his Ancestry Painting, due to the presumed presence of European ancestry among some of Roy’s African American ancestors. But other than that, the two illustrations of his ancestry look remarkably similar.

A Beautiful Ancestry Painting

<img loading="lazy" decoding="async" class="alignright size-medium wp-image-231" src="http://35.88.189.111/wp-content/uploads/2008/05/istock_000005569535xsmall-300x225.jpg" alt="" width="300" height="225" srcset="https://blogcms.23andme.com/wp-content/uploads/2008/05/istock_000005569535xsmall-300x225.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2008/05/istock_000005569535xsmall.jpg 400w" sizes="auto, (max-width: 300px) 100vw, 300px" />One of the most exciting aspects of archaeology is how new research can alter previously held notions about prehistoric events.
One of the most hotly debated events is the peopling of the Americas. Theories on the timing and specifics of the arrival of the first Americans are continuously modified as new evidence from fossil, paleoclimatic, and genetic records is examined.
<h2>First to the New World</h2>
A study in last month’s <a href="https://blog.23andme.com/2008/03/07/the-amazing-journey-a-new-synthesis-for-the-peopling-of-america/">American Journal of Human Genetics</a> argued for an ancient and fast migration of prehistoric humans across the Bering Strait and down the Pacific Coast based on a genetic analysis of present-day Native Americans. That study was provocative because it significantly pushed back the arrival date of humans to the New World to 18,000 years ago from the previous estimate of 13,000 years.
Now, results from a new study in this week’s Science further bolster that theory, using the prevalence of preserved seaweed as an indicator.
Anthropologists at Vanderbilt University excavated a South American archaeological site, Monte Verde II. In southern Chile, Monte Verde II is midway between the Pacific Coast and the Andes mountains. It dates to approximately 14,600 years ago, making it one of the oldest archaeological sites in the New World. The age of Monte Verde II, combined with its extreme southern location, lends additional support to the hypothesis of an early arrival of humans into South America.
<h2>Seaweed</h2>
The sheer abundance of preserved seaweed in various huts at Monte Verde II lends additional support for the initial migration occurring down the Pacific Coast rather than further inland. Seaweed is an incredibly fragile material and does not preserve well. However, remains of seaweed are found all over Monte Verde II. The authors think the seaweed was probably used extensively for food and medicinal purposes, which still continues in present-day coastal communities.
The presence of some foods from inland areas indicates that the inhabitants of Monte Verde also traveled inland at some point during the year or else mingled with other communities that did so.
So, how do these findings help us to understand the earliest inhabitants of the Americas? Most importantly, this study supports the idea that the first Americans traveled down the length of the Americas via the Pacific Coast. However, it also shows that there seems to be some relationship between coastal communities, such as Monte Verde, and those more inland groups.
In fact, the authors of this study use this possible relationship to propose a slight variation on the theme of a coastal migration route, saying that the first inhabitants may have taken a slower journey down the coast, spreading out in the interior along the way. Although this hypothesis needs additional support, it is clear that the debate on the people of the Americas is far from over.

It’s All About the Seaweed: New Theories on the Peopling of the Americas

Editor&#8217;s Note: This post does not reflect our current product offering. 23andMe&#8217;s ancestry product looks at the autosomes (chromosomes 1-22), the sex chromosomes (XY), and mitochondrial DNA (mtDNA). For more information about how results are different for men and women go here.
One of the most exciting parts of 23andMe’s <img decoding="async" class="right alignright" src="https://blog-api.23andme.com/wp-content/uploads/2008/05/gus.jpg" alt="gus.jpg">
<h6>Paternal vs. Maternal</h6>
At present, 23andMe customers can trace two branches of their genetic family tree — one that follows the all-female line on the maternal side (through mitochondrial DNA) and another the all-male line on the paternal side (through the Y chromosome).
Not all DNA is created equal, however: males have both mitochondrial DNA AND a Y chromosome, so they can trace both their maternal and paternal ancestry. Females, who have mitochondrial DNA but no Y chromosome, can trace only their maternal ancestry.
So how can females discover their paternal history? One solution is to ‘borrow’ the Y chromosome of her most immediate paternal ancestor — her father. A female can have her father send his own DNA sample to 23andMe, then examine his Y chromosome as a way of understanding his paternal ancestry and her own.
<h6>Discovering Paternal Ancestry</h6>
But what if a woman&#8217;s father can&#8217;t or won&#8217;t share his DNA? By sharing 23andMe accounts with the right male relative, a woman can still discover both her maternal and paternal ancestry.
So whose DNA can a female customer use, besides her father&#8217;s? It could be anyone who shares his Y chromosome — her brother, paternal uncle (father’s brother), or even paternal grandfather (father’s father). The chart below illustrates some of the possibilities in one woman&#8217;s family tree; male relatives who share her father&#8217;s Y chromosome are depicted in blue.
You may look at the chart and ask: Why not her son’s Y? After all, he&#8217;s a male relative, too. But even though a mother shares 50% of her genes with each of her children, only fathers pass Y chromosomes to their sons. So any examination of her son’s Y chromosome would yield not her father&#8217;s paternal history, but her husband&#8217;s.
<img decoding="async" src="https://blog-api.23andme.com/wp-content/uploads/2008/05/erinpaternal33.png" alt="erinpaternal33.png"> 
The woman whose family tree is shown here (&#8220;Me&#8221;) could determine her paternal ancestry using the Y chromosomes of males who are colored blue.

Whose Y to Use? Paternal Ancestry for Ladies

<img decoding="async" src="https://blog-api.23andme.com/wp-content/uploads/2008/04/siegeofacre1291.jpg" alt="siegeofacre1291.jpg" class="right alignright" />Generally, the DNA in a man&#8217;s Y-chromosome contains information about prehistoric migrations that happened many millennia in the past. But a recent study of men in Lebanon shows that genetics can be a reflection of more recent events as well.
A paper published in the April issue of the American Journal of Human Genetics shows that two major events in the history of religion — the spread of Islam and the Crusades — have left their mark on Lebanon&#8217;s male population.
The authors of the AJHG paper showed that a disproportionate percentage of Muslim men in Lebanon have Y-chromosomes of a type that is common on the Arabian peninsula. Migrants from Arabia brought Islam to Lebanon during the 7th century.
Similarly, a disproportionate number of Lebanese Christian and Druze men have Y-chromosomes similar to those found in western Europe. In fact, the most common Y-chromosome signature in Lebanon is most abundant in France, Spain, northern Italy and the Low Countries. But it is found nowhere else east of Hungary.

The authors of the AJHG paper attribute that remarkable genetic connection to the Crusades, a series of military campaigns by European invaders against Jerusalem and other cities of religious significance in the Near East.
There is also an indication that men from Turkey introduced their genes into the Lebanese population during the time of the Ottoman Empire, which ruled Lebanon from the 16th to 20th centuries.
In most countries, geography is the most significant factor influencing the genetic variability of the population. But in Lebanon, religion accounts for more than three times as much genetic variation as geography.
&#8220;Such structure might arise only when several unusual criteria are met,&#8221; the AJHG paper concludes. &#8220;Migrations based on religion must take place between areas with different representative Y-chromosomal types, and they must establish genetically differentiated communities that remain stable over long time periods. In Lebanon, these conditions appear to have been met for over 1,300 years.&#8221;
&#8220;The Siege of Acre&#8221; by Dominique Louis Papety (1815-1849)

Historical Genetics: Researchers Find Traces of Crusades, Spread of Islam in Lebanon

<div style="width: 435px" class="wp-caption alignright"><img loading="lazy" decoding="async" src="https://blog-api.23andme.com/wp-content/uploads/2008/03/birthcertificate.jpg" alt="birthcertificate.jpg" class="right" width="425" height="282" />Photo by Nancy Catherine Walker/iStockphoto</div>
If you were adopted, conceived through sperm donation or don’t know your parents for some other reason, 23andMe can give you a glimpse into your genetic legacy. Our service can’t help you locate your biological parents or reveal their medical histories — but it can provide some information about their heritage, and maybe even offer a few hints at some of their traits
Click <a href="https://www.23andme.com/dna-health-ancestry/">here</a> to learn more about what 23andMe&#8217;s Personal Genome Service can and can&#8217;t do with regard to unknown parents:
<h6> 
Ancestry</h6>
23andMe’s Personal Genome Service offers a number of different tools for probing your ancestry. The broadest view comes from the Global Similarity feature, which identifies the native populations around the world you most resemble genetically. It is likely the majority of your ancestors came from the one or two regional populations that are most similar to you.
The <a href="https://www.23andme.com/you/haplogroup/maternal/">Maternal Ancestry</a> feature offers a different vantage point, using one specific part of the genome to <a href="https://www.23andme.com/topics/ancestry/family-tree/">trace a single branch of your family tree</a> back in time and space. The results apply to only one branch — your mother’s all-female lineage — but they trace it all the way back to the origin of the human species about 200,000 years ago. As a result, the Maternal Ancestry feature gives you a very good idea of where your mother’s mother’s mother’s … family came from.
The <a href="https://www.23andme.com/you/haplogroup/paternal/">Paternal Ancestry</a> feature provides similar information, except that it provides information about a person’s all-male ancestral line. Because it analyzes DNA on the Y-chromosome, however, it is only available for men.
Finally, 23andMe recently introduced the Ancestry Painting feature, a new component of our service that could be of great interest to people who are uncertain about their heritage. Ancestry Painting examines each stretch of a person’s DNA and determines which of three continents it most likely came from — Africa, Asia or Europe. Because each person gets a complete set of chromosomes from each parent, the Ancestry Painting feature can tell an adopted person what continent each of his or her parents’ ancestors came from. The daughter of an African-American mother and an Asian-American father, for example, could easily see that signature in her Ancestry Painting.
<h6>Family Relationships</h6>
The data produced by 23andMe&#8217;s Personal Genome Serviceâ„¢ is not a tool to locate unknown parents. But it can be useful for determining the relationships between people. If you suspect another person might be related to you, you could test that theory (as long as that person also signs up for 23andMe and agrees to share profiles). For example, if you and a half-sibling compared yourselves to one another you would find that you share substantial stretches of half-identical DNA. 

<h6>
Health and Physical Traits</h6>
Most people make assumptions about some of the genetic variants they have inherited by looking at their parents and grandparents. A family history of heart disease, cancer or diabetes, for example, may indicate that a person has inherited some genetic predisposition for that particular ailment.
Naturally, people who do not know their parents have no idea about any disease-related genetic variants they might have inherited. While 23andMe does reveal some genetic information about genetic variations that have been associated with diseases and conditions, it does not offer a full enough view to establish a family history.
Because genetics is only one among many factors that can influence a person’s health and physical traits (and often only a minor factor!) there is very limited definitive information 23andMe can provide about unknown parents’ physical appearance or medical history. But even at this early stage of research, 23andMe can give you a glimpse at your parents’ DNA simply by showing you your own, along with the results of recent scientific studies that give it context. And over time, we hope to learn much more about how genetic information translates into <a href="https://www.23andme.com/dna-ancestry/">physical traits</a> and health outcomes.

Adoption and 23andMe: Filling Gaps in Your Family Tree

It was not very long ago — at least in evolutionary terms — that humans first ventured beyond the continent of their species’ birth. But once people did begin migrating out of Africa about 50,000 years ago to populate the lands we now call the Middle East, Asia, Europe and the Americas, the transformation of the species, and the planet, was swift.


Now, 2,000 generations later, 23andMe is launching a new feature that can help you see the traces of those ancient voyages in your chromosomes. As populations became separated over the millennia, small genetic differences developed that can still be used as signatures of geographic ancestry.
<h6>Coloring our Ancestry</h6>
Ancestry Painting looks at those signatures in the 22 numbered chromosomes (that is, all but X and Y) to infer where in the world the ancestors who passed you each stretch of DNA were most likely to have lived — Africa, Asia or Europe.

Ancestry Paintings essentially give you a snapshot of where your ancestors lived before the beginning of the colonial era about 500 years ago. That’s because the massive migrations that have occurred since then have blurred many of the genetic boundaries that had developed over the millennia. For example, most Americans trace their ancestry not to the continent where they live but to Africa, Asia, Europe or a combination of those places.
The best way to understand Ancestry Paintings is to take a look at some.
For example, this is the painting of a woman who has three grandparents from Germany and one from Norway:

Her painting is nearly uniformly navy blue, an indication that all of her chromosomes come from European ancestors. There are a few brief stretches of orange (meaning Asian ancestry), but in light of the overall pattern it is more likely that the orange stretches are statistical &#8220;noise&#8221; than indicators of true Asian descent.

<h6>African American Ancestry Painting</h6>

Now suppose that woman had a child with an African man. Because each person has 22 pairs of numbered chromosomes — one from each parent — Ancestry Paintings depict both in a single band. So the child of a mother with fully European ancestry and a father with fully African ancestry would have a painting consisting of 22 half-navy and half-green stripes.
It’s in subsequent generations that things really get interesting.
For example, this is the painting for a man who identifies himself as African American:
<img loading="lazy" decoding="async" src="https://blog-api.23andme.com/wp-content/uploads/2008/03/african-american-faq.png" alt="Ancestry Painting of African American Man" class="alignright" width="390" height="325" />
Genetic studies show that most African Americans have at least some European ancestry, and that finding is borne out by this man’s Ancestry Painting.
In fact, all the chromosomes are at least half blue, suggesting that this person has one parent of fully European ancestry. The solid blue color in some stretches indicates at least partial European ancestry for the other parent, whereas the stretches that are half blue and half green indicate African descent from one parent and European from the other. The overall fraction of each type of ancestry — African, Asian and European — is tabulated in the legend in the upper right of the display.
Log into your 23andMe account to find many more examples of paintings from individuals from around the world, along with descriptions of the events in human history underlying each and more detailed information about how to interpret them.

New Feature: Ancestry Painting

<img decoding="async" class="right alignright" src="https://blog-api.23andme.com/wp-content/uploads/2008/03/beringstrait.png" alt="beringstrait.png" />People who study the spread of humans to the Americas can agree on one thing — the first migrants crossed from Asia by way of a land bridge connecting Siberia and Alaska.
Just about everything else is subject to debate: who the people were, where they originated, when they migrated, how numerous they were and what they did once they crossed into the Americas.
Finally, a solution to the decades-old dispute may be at hand. That&#8217;s because genetic analyses are beginning to converge on a scenario that fits in with all the archaeological, linguistic, climatological and ecological data relevant to the issue — and also seems to make sense.
<h6> 
Rapid Migration</h6>
In this month&#8217;s issue of the American Journal of Human Genetics, researchers from Brazil and California argue that the present-day pattern of genetic diversity among Native Americans suggests a rapid southward migration along the Pacific coast that began about 18,000 years ago and took only a few thousand years to reach the tip of South America.
It was only later, the researchers claim, that people made their way inland in pursuit of large game animals such as woolly mammoth. The traditional view is that these mammoth hunters, who appear in the archaeological record about 13,000 years ago, were the first Americans.
This is not the first time a migration down the Pacific coast has been proposed. But the researchers were able to show by comparing the mitochondrial DNA of 86 Native Americans that all five of the major genetic branches in the New World trace back to an ancestral population of a few thousand people that began expanding rapidly around 18,000 years ago.
<h6>Coastal Route</h6>
At that time — not long after the peak of the Ice Age — glaciers thousands of feet thick blocked the land route from Alaska into the heart of North America. But the coast was clear. Recent research indicates the Pacific rim of North America was relatively ice-free by about 19,000 years ago.
The DNA evidence also offers information about the ancestral Asian populations that gave rise to the first Americans. The researchers compared the Native American DNA samples to their closest known relatives in Asia. It also found that the Asian and American lines appear to have split about 5,000 years before the rapid population expansion on the American side.
That suggests a long period of isolation. This was probably in the region that is now around (and underneath) the Bering Strait, before the first people flooded into the New World.
<h6>Native American Diversity</h6>
Two recent papers in the open-access journal Public Library of Science One suggest a similar scenario, albeit with slightly different dates. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0001596">One study</a>, published last month by University of Florida researchers, analyzed mitochondrial DNA donated by 77 Native Americans. That study found that the overall pattern of diversity was most consistent with a population that has experienced two episodes of rapid growth. The first was about 40,000 years ago, and period of growth happened about 15,000 years ago.
<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000829">A second study</a>, published last year by a global team of researchers, found that all of the major genetic branches of Native Americans appear to have started diversifying about 14,000 years ago. This was after being isolated for a long period of time.
The beauty of these genetic studies is their ability to explain the vexing archaeological evidence for the migration of people into the Americas. There are signs of humans living in Siberia, far from the major population centers of the time, as early as 30,000 years ago. And there is evidence of people at the Monte Verde archaeological site in southern Chile as early as 14,500 years ago.
Yet there are no archaeological sites intermediate between those two very distant locations in time and space. The genetic evidence suggest two reasons why. First, a small number of people migrating very quickly down the Pacific coast wouldn&#8217;t have left many artifacts behind. And second, if the migration happened shortly after the peak of the Ice Age, as the genetic evidence suggests, then the coastline it followed is now well offshore. Sea level has risen 120 feet since then.

Ancestry Service — Page 31