While one thousand people are to having their genomes mapped to understand how genes influence disease, it is also explaining world-history:
The Genographic Project is focusing on DNA from people still living in their ancestral homelands because they provide the crucial geographic link between genetic markers found today and routes traveled long ago. Population genetics using modern DNA can elucidate migration issues in historical as opposed to deep prehistorical periods. As descendants of the hunter-gatherers who first left humanity’s birthplace in east Africa some 65,000 years ago, they split off in different directions. Thus distinct mutations accumulated in the DNA of each population. Like bread crumbs, these genetic markers, passed on intact for millennia, can reveal the trail of the original pioneers. All non-Africans share a mutation that arose in the ancestors of the first people to leave the continent, for instance. But the descendants of those who headed north and lingered in the Middle East carry a different marker from those who went southeast toward Asia. Most of the world’s six billion people, however, are too far removed from wherever their ancestors originally put down roots to be useful to population geneticists. In its first 18 months, the project’s scientists have had considerable success, persuading more than 18,000 people in off-the-grid places like the east African island of Pemba and the Tibesti Mountains of Chad to donate their DNA. The first large effort to collect indigenous DNA since federal financing was withdrawn from a similar proposal amid indigenous opposition in the mid-1990s, the Genographic Project has drawn quiet applause from many geneticists for resurrecting scientific ambitions that have grown more pressing. As indigenous groups intermarry and disperse at an ever-accelerating pace, many scientists believe the chance to capture human history is fast disappearing.
The story of our map as of today, however, can be updated as such that we know our ancestors Homo erectus left Africa around 1.8 million years ago, settling in the tropical and subtropical zones of Central and East Asia. They died out approximately 100,000 years ago, except perhaps on remote islands in southeast Asia. The ancestors of the Neandenals left Africa around 500,000 years ago, but again their line died out. Today, humans are the only hominid species to leave descendants down to the present day. Even the early Homo sapiens who made it into the Middle East around 110,000 years ago died out 30,000 ago.The first humans to leave Africa likely followed the southern Indian coastline, reaching Australia.
The ancestors of modern western Europeans-the members of the Rl b clan-started wandering into Europe in earnest around 35,000 years ago, they encountered another hominid living there-the Neandertals, who would die out. Yet despite their advantage over the Neandertals, the newomers however would also forced into retreat as well by the cold European climate. As large ice sheets advanced across Scandinavia and Britain, the human population beat a retreat to the best possible place to sit it out-the beaches of the Mediterranean.
A few humans, ended up in Spain, Italy, and the Balkans, where the ice was kept at bay by the warm waters of the Mediterranean.But there was a stroke of good luck. The climate, for reasons that still aren't fully understood, started to change around 15,000 years ago. The weather warmed up, and the ice sheets began to retreat. Taking advantage of the situation, human populations started to advance back into northern Europe and took their genes with them. The current distributions of the European genetic lineages are largely due to this "overwintering" and subsequent expansion, coupled with the migrations of new haplogroups importing agriculture.
As humans were being pushed into a corner in Europe, their cousins in Asia were enduring a similar on slaught. Although small groups did live in the far north, for the most part Asians were forced into their own enclaves during the last ice age. Glaciers spreading from mountain ranges-the Hindu Kush, Tien Shan, and Himalaya hemmed them in to different corners of the continent. Indians were isolated in the subcontinent, and East Asians were restricted to their core territory farther east, perhaps in the area of Vietnam, Cambodia, and southern China.
Because humans at this time lived in small huntergatherer populations, genetic drift served to change gene frequencies over time, as these small groups split off from each other and migrated into new territory. Genetic drift, for instance, explains most of the genetic patterns we see for the mtDNA and Y-chromosome markers. As humans moved through Eurasia, then, the forces of genetic drift, climatic adaptation, and sexual selection combined to change their physical appearance. At the same time, other changes were taking place-changes in the languages they spoke, as well as cultural developments that allowed them to survive in their new locations. Southeast Asians would never need to create warm, fur-lined clothes, and Siberian hunters would not need to worry about sunburn most of the year. The early wanderings of our species helped to mold humanity's original African features-from language to skin color-into local, specialized varieties, producing the wide diversity we see around the world today. Most of the differences that distinguish us today probably arose during this period, within the past 40,000 years. While all of this was going on in Asia, the oldest continuously inhabited continent outside of Africa, with evidence for a human presence starting around 50,000 years ago is Australia.
Drawings discovered at Kimberley, in northwestern Australia, have depictions of human and animal figures. They were clearly created by humans, but it is unclear exactly when. How do we determine the age of a rock scratching-what sort of clock could we use? Here nuclear-dating methods fail us, since there is no way to carbon-date a figure etched in stone. Or is there? It turns out that there is a way, and it comes in the form of an ancient insect infestation. Archaeologists studying the artwork at Kimberley noticed an abandoned wasp's nest covering one of the figures, which means that it must have been built after the figure was scratched into the rock.The nest could have been constructed a hundred years ago, of course, in which case it wouldn't have been terribly useful for dating the ancient art. But when they tested it, using a technique known as optical luminescence, they were surprised to learn that it was about 17,000 years old, which dates back to the Paleolithic. Moreover, the wasp's nest was built over a human figure with an elaborate headdress, which makes this the oldest human depiction in the world (the drawings in European caves are almost all animals). Richard Roberts, the researcher who tested the nest, thinks the drawings may be substantially older than this, since the climate in Kimberley 17,000 years ago was much drier and would not have been a likely place for human habitation.
But farther south in New South Wales, near Sydney, human skeletons at Lake Mungo have been dated to between 45,000 and 50,000 years ago. This makes them the earliest modern humans ever found outside of Africa, predating the evidence in Asia by roughly 10,000 years. Is it possible that these people could have sailed directly from Africa to Australia, bypassing the Arabian Peninsula, India, and southeast Asia?
This conundrum has long puzzled archaeologists, with extreme views dominating the debate. Some have argued that modern Australians are the descendants of Homo erectus in southeast Asia, suggesting that they entered Australia 100,000 years ago or more. Others have theorized an influx of modern humans within the past 10,000 years. The truth lies somewhere in the middle, and genetics has garnered the clues necessary to answer the question.
Modern Australian Aborigines are not descended from erectus or other human cousins. Their DNA, while quite different from that found in people living in Asia due to their long period of isolation, is clearly part of the modern human lineage. Like all other non-African lineages, Australian Aborigines ultimately trace their ancestry back to Africa . So how did humans make it to Australia without apparently passing through Asia?
Today we live in a benign, relatively warm period known as an interglacial, but in the past the world was a much colder place. The same effect that gave rise to the Bering land bridge and allowed people to walk into the Americas from Siberia changed sea levels worldwide. A drop of 100 meters, or more than 300 feet, has been documented at various times during the last ice age because the water was tied up in the great ice sheets of the far north. While this amount may not seem like much (it's not much taller than a small skyscraper), the vertical difference is less important than what happened to the land area. Australia is no longer an island continent. Rather, it is joined to New Guinea as part of the ancient continent of Sundaland.
This is because the Torres Strait separating the two countries is quite shallow, even though the currents are very strong. Even today Australia and New Guinea retain similar animal and plant species in the tropical zone, with oddities such as the velociraptor-like cassowary, a five-foot-tall predatory bird found in both northern Queensland and across the strait in the forests of New Guinea. The similar flora also reflects their ancient history as joined landmasses. In the same way, other landmasses were much larger 50,000 years ago. The western coast of India would have been as much as 200 kilometers west of where it is today, and Sri.Lanka would have been joined to it. Most of island Malaysia would have been joined to the peninsula.
Overall, the coast would have been very different. It is likely that this is the reason that there is no trace of modern humans along the early route to Australia . Their camps are underwater today, subsumed under the rising sea levels of the past 10,000 years. It suggests that the best place to look for evidence of an early human presence in Asia might not be inland, but rather along the near-shore ocean bottom. Intriguingly, the earliest evidence of modern humans in the Indian subcontinent has been found in a cave near the Sri Lankan shore, suggesting a treasure trove of Paleolithic stone tools may lie just under the water's surface.But if the archaeological evidence fails to provide us with the clues we need to determine the route early Australians took, perhaps genetics can find the trail in the people living in Asia today.
Humans migrating from Africa may have passed through India en route to populate the rest of southern Asia and Australia. But tests on several hundred samples collected in southern India late 2005, showed a clear genetic link to Australia. The genetic link between his Y chromosome and Australia came in the form of a marker known as RPS4Y The lineage found in southern Indians is directly ancestral to the same C lineage found in Australians. This tells us that C appeared first along the coastal route leading to Australia from Africa, and only later did it migrate inland to Mongolia, probably via the coast of East Asia.
Haplogroup C3 seems to have continued its coastal journey all the way into the Americas, where some North American populations have fairly high frequencies of this lineage. These groups typically belong to those speaking the Na-Dene languages, the second major linguistic family in North America. From the age of the C3 lineages in North America it appears that the ancestors of the Na-Dene speakers entered the continent only in the past 8,000 years.
The Indian and southeast Asian distributions clearly show that the descendants of these early coastal migrants are a minority today. Most people in India, and in fact, more than 95 percent of Y chromosomes and 50 percent of mitochondrial lineages in Eurasia, Australia, and the Americas, trace their ancestry back to a different migration-the one that led ancestors into Central Asia 40,000 years ago-an inland route through the Middle East. This new group of migrants would become one of the most influential in the spread of humans worldwide.
During the last ice age, when sea levels were dropping along the coastal route that led to India, inland conditions were also changing. Because of the generally drier conditions, the savannas of East Africa were expanding into areas that had formerly been forest. The Earth's climate was going through a period of erratic weather, with rapid increases in temperature interspersed among the generally lower temperatures. The result was that humans were pushed and pulled in many directions, their range alternately expanding and contracting. There is evidence that the Sahara was sometimes wetter than it is today, as well as drier. During the wetter phases savanna would have intruded into today's desert zone, allowing humans and the animals they hunted to move northward.
These early bands of hunting and gathering humans would have been drawn into the expanding grasslands by a wetter climate, but worsening conditions could also have pushed them out. The neurobiologist William Calvin, who has written on the effects of climate change on early human evolution, compares the Sahara during this period to a kind of pump, drawing in animals from other regions during wetter phases and expelling them when the weather turned drier.
During one of these ourward-pumping phases a small group of hominids left Africa 45,000 to 50,000 years ago and entered the Middle East. The exact route they took is unknown, although current Genographic work on the populations of the Sahara-particularly those in Chad, Sudan, and Egypt -should shed some light on this. By 45,000 years ago, this small band was well established in the Middle East and left behind ample evidence in the form of skulls, tools, and other archaeological material. There is also a unique genetic marker called M89, the ancestor of much of the male population of the Northern Hemisphere. M89 appears to have been accompanied on his journey through the grasslands by a woman belonging to the mitochondrial DNA clan N, who also left Africa for the Middle East around this time.
This was not the first time that humans had migrated to the Middle East. Skulls and other fossilized remains belonging to the Homo sapiens, dating to 100,000 years ago, have been found at Qafzeh and Skuhl caves. But then they suddenly vanish about 30,000 years later. There is a long gap in the fossil record between their disappearance and when humans reappear in the Middle East about 50,000 years ago.Once they were established on the Asian landmass, though, these people spread rapidly. According to the genetic evidence, these inland populations moved quickly into Central Asia and India, with one line leading to Phil's ancestors via markers M9 and M45. M89 and haplogroup N's descendants also spread into India and reached East Asia soon after. Early humans probably took only 10,000 years to colonize the majority of the Asian landmass below the Arctic. This final frontier would have to wait until Phil's ancestors made their icy trek 20,000 years ago.The inland clans-M89 and mtDNA-N-soon expanded across regions formerly inhabited only by the coastal clans defined by M130 and mtDNA-M. Why they were so successful is unknown-perhaps their populations had developed cultural attributes that gave them an advantage. Clearly, though, frequencies of the coastal lineages today are a fraction of their former levels, with almost all Indian men tracing their ancestry back to the incoming grassland populations.
Still open questions that we are currently looking into are:
Canada, the United States, Mexico, and the Caribbean: How many waves of migration were there to the Americas, and was one of the earliest migrations along the west coast? Could Europeans have migrated to the Americas thousands of years ago? Is there a genetic signal from the expansion of indigenous American agriculture-i.e., did the farmers or their culture move?
South America: Were there any migrations to South America from the Pacific? Did the Inca Empire have a genetic Impact on northwestern South America? How do we account for the extraordinary linguistic diversity found in native South Americans? Have populations there been separate for a long period of time? Can we find genetic signals of now extinct groups, like the Arawak in the Caribbean , in today's admixed populations?
Europe: Was there any mingling between modern humans and Neandertals during the European Upper Paleolithic? What route(s) did modern humans take in their settlement of Europe? Did the Celtic expansion of the mid-first millennium B.C. leave a genetic trail? Can we detect historical migrations during the past 2,000 years in to day's European populations Normans in Sicily , or the spread of Finno-Ugric languages in Eastern Europe? Middle East and North Africa: Did important imperial conquests have an impact on the genetic landscape of the conquered regions? For instance, did Alexander the Great's armies leave a genetic trail? Where did the Afro-Asiatic languages, including Arabic and Hebrew, originate? Who were the aboriginal inhabitants of North Africa, and are the Berbers their direct descendants? How much genetic exchange has there been across the Sahara?
Sub-Saharan Africa: the most genetically diverse part of the world where questions are; Which African populations harbor the most ancient genetic lineages, perhaps suggesting a geographic origin for modern humans? How has European colonialism had an impact on the genetic patterns in Africa? Can we trace the origins of the Bantu people-and their expansion across Africa -from genetic patterns? Was there a separate domestication of cattle in Africa? Did this lead to a population expansion?
India, probably the oldest continuously inhabited region outside of Africa. Its 400-plus languages and complex social system make sampling a tremendously challenging proposition. So we are asking: Where did the Dravidian speakers originate? Were they the "first" Indians? What role has the Indian caste system had in determining genetic patterns? Where did so called, Indo-European speakers originate, and what languages were being spoken prior to their spread in Europe and Asia?
Middle East and North Africa: Did important imperial conquests have an impact on the genetic landscape of the conquered regions? For instance, did Alexander the Great's armies leave a genetic trail? Where did the Afro-Asiatic languages, including Arabic and Hebrew, originate? Who were the aboriginal inhabitants of North Africa, and are the Berbers their direct descendants? How much genetic exchange has there been across the Sahara?
West Asia: When and where did modern humans first colonize the Arctic? Who were the first inhabitants of the Caucasus region, and why is there such incredible linguistic diversity there? What role did the Silk Road play in dispersing genetic lineages?
East Asia: How has the geography of China molded genetic patterns there? Who were the aboriginal inhabitants of Indonesia? Was there much genetic exchange with Australia? Was there any mingling with Homo erectus as modern humans spread throughout Southeast Asia? What are the patterns of genetic variation in New Guinea? Do they parallel the extraordinary linguistic diversity there?
Australia/New Zealand: How do the genetic patterns in Australia correlate with the Aboriginal songlines-their own oral histories? Can one use genetics to trace the spread of the Polynesians from island to island in the Pacific? Is it possible to obtain intact DNA from the remains of Homo erectus and other extinct hominid species, allowing us to resolve many debates in the field of paleoanthropology and early human history? Can ancient DNA be used to observe changes in the genetic composition of a population over time?
Referred to as “Genome-wide detection of human copy number variations” to be published soon in Genome Research, shows a variation in the genetic make-up of humans that could lead to a fundamental reappraisal of what causes incurable diseases, noticing differences between African, Asian and European groups.