DNA News Page 1  -  Last update 10/5/2012

-- FTDNA 5/19/2006:  New 59 marker test upgraded to 66 - 5/23/06
-- In the News: Family Tree DNA Announcement - 12/27/05
-- Founding Families: New World was settled by small tribe - 2/28/05
-- Our Species Mated With Other Human Species, Study Says - 3/06/02
-- Human Genome Shows Proof of Recent Evolution, Survey Finds - 3/08/06
-- Did Climate Change Trigger Human Evolution? - 2/02/06

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 FTDNA 5/19/2006:  New 59 marker test upgraded to 66.

We are excited to announce that the lab was able to add an additional panel of markers and will be reporting to you a total of 66 markers!  While this has caused a slight delay, we feel it is worth it to provide the most complete set of results possible to our customers.

5/23/2006: In the mean time they have expanded one extra marker to 67.

 In the News: Family Tree DNA Announcement

12/27/2005 - Family Tree DNA now has over 50,000 Y-DNA records and 15,000 mtDNA records in our database. We also have over 2,600 Surname Projects, which include over 28,000 surnames.

Having at least 4 times the combined data of all other databases of this kind in the world, the size of the database is an important feature to look at when choosing the company to test with, as the larger the database you are compared with, the richer the information you will be obtaining, whether it's about matches or about your ancestral origins.

 Founding Families: New World was settled by small tribe

Science News - Week of May 28, 2005; Vol. 167, No. 22 , p. 339  -  Bruce Bower

A geneticist armed with computer simulations of prehistoric populations says that only about 200 to 300 people crossed the ice age land bridge from Asia to become the founding population of North America. Of that pioneering group, there were just 70 adults of reproductive age, contends Jody Hey of Rutgers University in Piscataway, N.J.
MAPPING THE PAST. An analysis of DNA from inhabitants of areas designated by colored circles on this map suggests that the New World was initially settled by a single tribe. Size of circles increases with the sample size, and different colors indicate different genetic locales.

Hey arrived at that strikingly small number after analyzing DNA from living Asians and Native Americans. Using nine specific DNA sequences as reference points, he inferred the movements and characteristics of the ancient population, including the Americas' founding fathers and mothers.

"It looks like a group that was about the size of a single tribe made the initial trip from Asia to the New World," Hey says. His findings appear in the June PLoS Biology.

To investigate ancient populations, scientists take samples from modern people and compare genetic locales that show no signs of having been shaped by natural selection, so random mutations probably have accumulated there at a regular rate. In earlier studies, researchers examined single sequences to reconstruct the initial New World population size. Those sequences reside either within mitochondrial DNA, which is passed on exclusively by the mother, or on the Y chromosome, which travels only from father to son. Previous estimates of the newcomer population have ranged from about 100 to 1,000 reproductive-age adults.

Hey, in contrast, used previously collected data to simultaneously assess differences in one mitochondrial DNA sequence and in eight stretches of DNA distributed among several chromosomes in the nucleus. Data on each genetic sequence came from 5 to 50 northeastern Asians and from comparable numbers of speakers of Amerind tongues, the oldest of three major Native American–language groups.

The Rutgers scientist fed the DNA data into a computer program that compared millions of possible scenarios for how patterns of genetic differences arose in the two populations, highlighting the most likely ones.

Hey's analysis indicates that between 14,000 and 7,000 years ago, approximately 200 to 300 people entered the New World after leaving an Asian population that was roughly 100 times as large. Geneticists typically assume that about one-third of any population is fertile adults. Hey acknowledges that the timing of the migration in his analysis is more recent than other estimates, which range from 20,000 to 16,000 years ago.

Hey's approach represents "a big step forward," remarks geneticist Michael F. Hammer of the University of Arizona in Tucson. The new results bolster the view that small, isolated populations settled the Americas, he says.

Geneticist Theodore Schurr of the University of Pennsylvania in Philadelphia calls the new study "a solid, but initial, effort." Analyses of DNA sequences from larger numbers of Asians and Native Americans could yield different estimates of the founding population in the New World, Schurr adds.

Archaeologist David J. Meltzer of Southern Methodist University in Dallas notes that, since the ice age, only limited numbers of people have inhabited northeastern Asia's harsh terrain. Says Meltzer: "That the founding population [of the New World] looks to be about 70 folks surprises me not at all."

 Our Species Mated With Other Human Species, Study Says

Hillary Mayell for National Geographic News March 6, 2002

A new piece of evidence—one sure to prove controversial—has been flung into the human origins debate.

A study published March 7 in Nature presents genetic evidence that humans left Africa in at least three waves of migration. It suggests that modern humans (Homo sapiens) interbred with archaic humans (Homo erectus and Neanderthals) who had migrated earlier from Africa, rather than displacing them. [Later DNA testing may have proven this incorrect, some test done find no Neanderthal DNA in modern human populations].  In the human origins debate, which has been highly charged for at least 15 years, there is a consensus among scientists that Homo erectus, the precursor to modern humans, originated in Africa and expanded to Eurasia beginning around 1.7 million years ago.

Beyond that, opinions diverge.

There are two main points in contention. The first is whether modern humans evolved solely in Africa and then spread outward, or evolved concurrently in several places around the world.  The second area of controversy is whether modern humans completely replaced archaic forms of humans, or whether the process was one of assimilation, with interbreeding between the two groups.  "There are regions of the world, like the Middle East and Portugal, where some fossils look as if they could have been some kind of mix between archaic and modern people.  The question is, if there was mixing, did some archaic genetic lineages enter the modern human gene pool?  Yet we have no evidence of those genes—as is indicated from the mitochondrial DNA and y chromosome data—why not?" " said Rebecca Cann, a geneticist at the University of Hawaii.

Alan Templeton, a geneticist at Washington University in St. Louis who headed the study reported in Nature, has concluded that yes, there was interbreeding between the different groups. "We are all genetically intertwined into a single long-term evolutionary lineage.  To reach his conclusion, Templeton performed a statistical analysis of 11 different haplotype trees.  Templeton also concluded that modern humans left Africa in several waves—the first about 1.7 million years ago, another between 800,000 and 400,000 years ago, and a third between 150,000 and 80,000 years ago

A haplotype is a block of DNA containing gene variations that researchers believe are passed as a unit to successive generations. By comparing genetic differences in haplotypes of populations, researchers hope to track human evolution.

Alison S. Brooks, a paleoanthropologist at George Washington University, is more cautious about Templeton's conclusions. "Archaeological evidence supports multiple dispersals out of Africa," she said. "The question has always been whether these waves are dead ends. Did all of these people die? Templeton says not really, that every wave bred at least a little bit with those in Eurasia.  "This has not been the majority viewpoint of geneticists up to this point," said Brooks.

Dueling Theories

The fossil record shows that about 100,000 years ago, several species of hominids populated Earth.  Homo sapiens could be found in Africa and the Middle East; Homo erectus, as typified by Java Man and Peking Man, occupied Southeast Asia and China; and Neanderthals roamed across Europe.  By about 25,000 years ago, the only hominid species that remained was Homo sapiens.  Scientists have conducted a considerable amount of both genetic and archaeological research in an effort to understand how this outcome occurred.

The two primary theories in the human origins debate are the "Out of Africa" theory and the multi-regionalism theory. Each has its own variations, and there are intermediate models, such as one favoring assimilation among the different groups. Credible evidence exists to support each theory.

The multi-regionalism theory, which relies on fossil evidence, holds that after members of Homo erectus first left Africa roughly 1.7 million years ago, they settled in different regions of the world and evolved separately but concurrently into Homo sapiens. Despite the vast distances, there was enough gene exchange between groups that an entirely new species did not evolve.

The "Out of Africa" theory relies considerably on DNA evidence. This scenario also holds that Homo erectus first left Africa around 1.7 million years ago. Evolution continued, and anatomically modern humans appeared in Africa between 200,000 and 100,000 years ago.  Beginning about 100,000 years ago, these modern humans expanded outside the continent, making their way across Asia and Europe, where they completely replaced the older species, Homo erectus.  Unlike Templeton's assertions, the "Out of Africa" theory does not support the idea of interbreeding between archaic and modern humans.

Guarded Support

Explaining his contention that interbreeding occurred, Templeton said humans "have long shown a pattern of isolation by distance," and at any given time there is some degree of genetic difference between human populations.  "However," he added, "genetic interconnections have long existed among human populations, and this was accentuated by the latest 'Out of Africa' expansion, not eliminated, as under the replacement model."

Templeton's view is "a kind of compromise," said Brooks. "Africa was still the major source of all modern humans, but there was a limited amount of interbreeding with other populations already living in Eurasia," she said.  Fred Smith, a paleoanthropologist at Northern Illinois University who proposed the assimilation model of human evolution, said Templeton's data support the idea that modern humans evolved in Africa, spread to other continents, and interbred with archaic populations.  "I argued for the assimilation model based on morphology—what could be seen in the fossil record, rather than on genetic evidence.  But I'm in agreement with what Templeton has found," Smith said.

Cann, in an accompanying article in Nature, said Templeton's attempt to view the data from a global perspective is over-ambitious given problems with genetic studies of small-scale modern populations.  "I want to see [his methodology and analysis] validated in an area of the world where a variety of scientists from different disciplines think they understand how humans spread and when," she said.  Examples of human migration that might help demonstrate the validity of Templeton's analysis and its limitations, she suggested, include the relatively recent expansion to Polynesia, the spread of farmers from Turkey into Northern Europe, and the migration of Vikings to Iceland.

"We need lots of different tools to study human evolution," Cann pointed out. "Scientists get into trouble when they expect one tool will do everything. Sometimes you need a hammer to attach things, sometimes a screwdriver, and sometimes Velcro works as well!  "Better to keep exploring these different methods with an open mind," she added, "since there are things only fossils can tell you, and things only genetics can reveal."

 Human Genome Shows Proof of Recent Evolution, Survey Finds
Scott Norris for National Geographic News  March 8, 2006

Signs of recent evolution by natural selection are widespread across the human genome, experts say. Genome researchers at the University of Chicago have identified more than 700 regions in human DNA where apparently strong selection has occurred, driving the spread of genes linked to a broad range of characteristics.  "These are very recent events—within the past ten thousand years," said Jonathan Pritchard, a geneticist whose laboratory team conducted the study.

The results suggest that humans in different regions have continued to adapt in numerous ways to both environmental changes and cultural innovations.  Many of the genetic changes Pritchard's group detected came during or after the emergence of agriculture, beginning about 10,000 years ago, and long after the formation of modern human populations.  Some of the genes most strongly affected by selection were those associated with skin color, bone structure, and the metabolism of different foods.

Using newly available data, the scientists conducted a genome-wide scan for genetic variants showing evidence of recent selection in European, Asian, and African populations.  Most of the selected genes varied strongly among the three groups, suggesting that humans were adapting to pressures specific to different parts of the world.  The results are published in this month's issue of the journal PLoS Biology, "Changing World, Changing Genes".

Positive selection occurs when a specific gene gives its carriers some advantage over others who lack the gene.  The methods used by Pritchard's group detected apparently beneficial genes that have spread through a large portion of the population but are not yet universal.  The findings, along with other recent studies, begin to provide a kind of genetic narrative of recent human evolution.

Joshua Akey, a genetics researcher at the University of Washington in Seattle, says selection-driven changes recorded in the genome provide tantalizing clues about past challenges faced by humans.  "Recent human history was a time of rapid change in population size, diet, pathogen exposure, and culture," Akey said.  "These are all potentially strong selective forces, which Dr. Pritchard and his colleagues appear to have captured in their analysis."   For example, major changes in diet occurred as nomadic hunter-gatherers slowly shifted to a settled agricultural existence.

Pritchard says this transition left a legacy of strong selection on genes associated with the processing of carbohydrates and fatty acids.  The clearest example—one previously known about by researchers—is the gene that allows for the digestion of milk into adulthood.  Among Europeans, whose ancestors relied on milk products as an important food source, this gene has become widespread. In most other human populations the gene is rare.

The study also provides new evidence that mutations to better digest different food products have spread in other groups. 
Asian and African populations showed selection in genes affecting the metabolism of the plant sugars mannose and sucrose. 
All three groups also showed selection for different genes involved in the uptake, storage, and energy conversion of dietary fats.

Another previously unreported example of natural selection involves the genes that people today rely on to process most pharmaceutical products.  Changes in these genes may be a legacy of human exposure to toxic plant compounds, either through a diet of wild foods or deliberate medicinal uses.

Physical Differences

Genes related to physical characteristics also showed strong evidence of selection, with interesting differences among the three populations.  "We found five different genes involved in skin pigmentation in the European population," Pritchard said.  He noted that, for humans living far from the equator, lighter skin is important for producing vitamin D, which is often formed in the body following exposure to the sun's ultraviolet rays.  Pritchard says evidence of recent pigmentation changes in Europeans may be the tail end of a much older process underway since modern humans first moved out of Africa or Asia to higher latitudes.  But the genetic changes could also be a reflection of more recent northward migrations following the last Ice Age, about 14,000 years ago, he says.

The survey also turned up evidence of selection in genes affecting skeletal development in Europeans and Asians and hair formation in Africans.  Pritchard says that while proteins involved in these processes were clearly targeted, it is still too early to say exactly why the changes occurred or what the evolutionary outcomes may have been.

Disease Selection

Evidence of different selective pressures operating on different populations may be medically important, says study lead author Benjamin Voight.  Discovering genes that contribute to common human diseases is always difficult, Voight said.  But "our hope is that the identification of selective targets using evolutionary theory might give other researchers a starting point."   Many disease-related genes should leave a strong signal of selection, because they influence individual survival.  By examining how selection has operated on different populations, researchers may be able to track down the genes underlying conditions such as diabetes, hypertension, and obesity, which vary in incidence and severity across ethnic groups.  "This research may provide the foundation for understanding how human evolutionary history has contributed to the susceptibility to complex diseases," the University of Washington's Akey said.  "Genome-wide scans for selection are not an end but rather an exciting beginning."

 Did Climate Change Trigger Human Evolution?
James Owen for National Geographic News  February 2, 2006

It may be a threat to humans' long-term future on the planet, but climate change may have helped bring us into being in the first place, some scientists say.  Some human-origins theories suggest that ancient climate changes acted as powerful evolutionary drivers, spurring our ancestors to stand tall on two legs, grow large brains, and develop other human traits (related reading: "Was Darwin Wrong?").  The evolution of early human species, so the theories go, was concentrated in periods marked by fluctuating environmental conditions.

Other theories suggest that humankind emerged independently of climatic swings, with adaptations arising, for example, out of competition between or within species.  While more evidence is needed to settle the debate, experts say the answer may lie at the bottoms of ancient African lakes.  The main challenge for researchers is to find out whether prehistoric shifts in climate coincided with key stages of development in the early human fossil record, writes ancient-biology expert Anna K. Behrensmeyer in tomorrow's issue of the journal Science. Behrensmeyer is a paleobiologist at Washington, D.C.'s National Museum of Natural History.  Records of ancient global climate change come mainly from ocean sediments. These suggest cooler, drier, and more variable conditions kicked in some three million years ago.

Early Human Fossils

Differing amounts of dust blown from the land into these seabed sediments indicate that continents were affected as well as the oceans.  But, Behrensmeyer said, "in the continental basins that preserve hominid [early human] fossils, the record of climate change is much harder to decipher."  Geological forces, including erosion and tectonic movements, have largely obscured or erased such evidence, she said. 

Humans are thought to have evolved in the Great Rift Valley region of East Africa. Studies have linked our forebears' emergence to drier conditions, as indicated by the ocean records.  Researchers say the growth of arid grasslands at the expense of tropical forests may have prompted the first humans to split off from other primates.  For instance, a study in the journal Nature in 2004 identified adaptations for running in human fossils more than two million years old. These adaptations may have enabled early humans to chase down prey on the open plains of Africa, researchers said. (See "Humans Were Born to Run, Fossil Study Suggests.")   More recent research, published last year in Science, suggested that a period of more sudden, regional climate fluctuation played a key role in human development.   Analysis of soil layers in the Great Rift Valley showed evidence for three unusually wet periods between 2.7 and 1 million years ago.  Fossils of aquatic algae indicated the presence of extinct lakes, some more than 328 feet (100 meters) deep, which quickly formed then disappeared.  Researchers say the lakes are evidence of the type of rapid climate swings that might have driven human evolution, forcing populations to adapt and readapt to cope with fast-changing environmental conditions.

"Strong Evidence"

"These temporary humid periods would have imposed huge impacts on early humans, and our research provides strong evidence for theories in which early human species evolved and spread out in response to a rapidly changing environment," said Mark Maslin, a co-author of the new study and a prehistoric-climate scientist at University College London, England.

But Behrensmeyer, the ancient-biology expert, said it remains unclear how fluctuating lake levels "could have exerted selective pressure on the immediate ancestor of Homo and resulted in the emergence of [the first humans]."   There is also uncertainty over the precise time and place of humanity's origin, she adds. Estimates range from 2.6 million to 1.7 million years ago. (Read "Did Early Humans First Arise in Asia, Not Africa?")   Behrensmeyer says samples from the bottoms of some of the world's oldest lakes, in East Africa, should provide more complete data "and a stronger bridge between oceanic and continental climate records."   Unlike sediment records found on land, the beds of deep tropical lakes are thought to hold relatively undisturbed records of climate change laid down in layers over thousands of years.

Now an international team of scientists hopes to get a better picture of African and global climate history from mud drilled up from the bottom of Lake Malawi in the Great Rift Valley.   The samples, dated to as many as 1.5 million years ago, should enable researchers to make detailed comparisons with climate change records from temperate and polar regions, according to lead researcher Christopher A. Scholz, of the Department of Earth Sciences at Syracuse University in upstate New York.

The project should uncover "an archive of environmental change that occurred in concert with human evolution," Scholz said.

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