And Neanderthals, as far as we know, had nothing like the etching at Blombos Cave, let alone the bone carvings, ivory flutes and, ultimately, the mesmerizing cave paintings and rock art that modern humans left as snapshots of their world. When the study of human origins intensified in the 20th century, two main theories emerged to explain the archaeological and fossil record: one, known as the multi-regional hypothesis, suggested that a species of human ancestor dispersed throughout the globe, and modern humans evolved from this predecessor in several different locations.
The other, out-of-Africa theory, held that modern humans evolved in Africa for many thousands of years before they spread throughout the rest of the world. In the s, new tools completely changed the kinds of questions that scientists could answer about the past.
By analyzing DNA in living human populations, geneticists could trace lineages backward in time. These analyses have provided key support for the out-of-Africa theory. Homo sapiens , this new evidence has repeatedly shown, evolved in Africa, probably around , years ago. The first DNA studies of human evolution didn't use the DNA in a cell's nucleus—chromosomes inherited from both father and mother—but a shorter strand of DNA contained in the mitochondria, which are energy-producing structures inside most cells.
Mitochondrial DNA is inherited only from the mother. Conveniently for scientists, mitochondrial DNA has a relatively high mutation rate, and mutations are carried along in subsequent generations. By comparing mutations in mitochondrial DNA among today's populations, and making assumptions about how frequently they occurred, scientists can walk the genetic code backward through generations, combining lineages in ever larger, earlier branches until they reach the evolutionary trunk.
At that point in human history, which scientists have calculated to be about , years ago, a woman existed whose mitochondrial DNA was the source of the mitochondrial DNA in every person alive today. That is, all of us are her descendants. Scientists call her "Eve. But she did live at a time when the modern human population was small—about 10, people, according to one estimate. She is the only woman from that time to have an unbroken lineage of daughters, though she is neither our only ancestor nor our oldest ancestor.
She is, instead, simply our "most recent common ancestor," at least when it comes to mitochondria. Subsequent, more sophisticated analyses using DNA from the nucleus of cells have confirmed these findings, most recently in a study this year comparing nuclear DNA from people from 51 parts of the world.
This research, the most comprehensive to date, traced our common ancestor to Africa and clarified the ancestries of several populations in Europe and the Middle East. While DNA studies have revolutionized the field of paleoanthropology, the story "is not as straightforward as people think," says University of Pennsylvania geneticist Sarah A. If the rates of mutation, which are largely inferred, are not accurate, the migration timetable could be off by thousands of years.
To piece together humankind's great migration, scientists blend DNA analysis with archaeological and fossil evidence to try to create a coherent whole—no easy task.
A disproportionate number of artifacts and fossils are from Europe—where researchers have been finding sites for well over years—but there are huge gaps elsewhere. As the gaps are filled, the story is likely to change, but in broad outline, today's scientists believe that from their beginnings in Africa, the modern humans went first to Asia between 80, and 60, years ago.
By 45, years ago, or possibly earlier, they had settled Indonesia, Papua New Guinea and Australia. The moderns entered Europe around 40, years ago, probably via two routes: from Turkey along the Danube corridor into eastern Europe, and along the Mediterranean coast.
By 35, years ago, they were firmly established in most of the Old World. The Neanderthals, forced into mountain strongholds in Croatia, the Iberian Peninsula, the Crimea and elsewhere, would become extinct 25, years ago. Finally, around 15, years ago, humans crossed from Asia to North America and from there to South America.
Africa is relatively rich in the fossils of human ancestors who lived millions of years ago see timeline, opposite. Lush, tropical lake country at the dawn of human evolution provided one congenial living habitat for such hominids as Australopithecus afarensis. Many such places are dry today, which makes for a congenial exploration habitat for paleontologists. Wind erosion exposes old bones that were covered in muck millions of years ago.
Remains of early Homo sapiens , by contrast, are rare, not only in Africa, but also in Europe. One suspicion is that the early moderns on both continents did not—in contrast to Neanderthals—bury their dead, but either cremated them or left them to decompose in the open. In , a team of anthropologists reported the discovery of three unusual skulls—two adults and a child—at Herto, near the site of an ancient freshwater lake in northeast Ethiopia.
The skulls were between , and , years old and had modern characteristics, but with some archaic features. Yet they are so close you wouldn't want to give them a different species name. The Herto skulls fit with the DNA analysis suggesting that modern humans evolved some , years ago. But they also raised questions. There were no other skeletal remains at the site although there was evidence of butchered hippopotamuses , and all three skulls, which were nearly complete except for jawbones, showed cut marks—signs of scraping with stone tools.
It appeared that the skulls had been deliberately detached from their skeletons and defleshed. In fact, part of the child's skull was highly polished. Even more provocative were discoveries reported last year.
In a cave at Pinnacle Point in South Africa, a team led by Arizona State University paleoanthropologist Curtis Marean found evidence that humans , years ago were eating shellfish, making complex tools and using red ocher pigment—all modern human behaviors.
The shellfish remains—of mussels, periwinkles, barnacles and other mollusks—indicated that humans were exploiting the sea as a food source at least 40, years earlier than previously thought. The first archaeological evidence of a human migration out of Africa was found in the caves of Qafzeh and Skhul, in present-day Israel.
These sites, initially discovered in the s, contained the remains of at least 11 modern humans. Most appeared to have been ritually buried. Artifacts at the site, however, were simple: hand axes and other Neanderthal-style tools. But conditions gradually deteriorated until ice covered much of the European landmass, reaching a peak 27, years ago. The ice melted rapidly after 10, years ago, allowing populations from the south to re-populate northern Europe - during a time known as the Mesolithic.
But the genetic relationships between pre- and post-Ice Age Europeans have been unclear. Some researchers have in the past raised the possibility that pioneer populations in Europe could have gone extinct some time during the last Ice Age.
And one recent study looking at the skull features of ancient Europeans found that Upper Palaeolithic people were rather different from populations that lived during the later Mesolithic period. In the latest study, an international team of researchers sequenced the genome the genetic "blueprint" for a human of a man buried in Kostenki, Russia.
They discovered a surprising genetic "unity" running from the first modern humans in Europe, through to later peoples. This, they claim, suggests that a "meta-population" of Palaeolithic hunter-gatherers managed to survive the Ice Age and colonise the landmass of Europe for more than 30, years.
Old cultures died and new ones emerged - such as the Aurignacian and the Gravettian - over thousands of years, and the hunter-gatherer populations ebbed and flowed. She added: "It is only when famers from the Near East arrived about 8, years ago that the structure of the European population changed significantly. Health Health is a priority for most Europeans and can literally be a matter of life and death.
Life expectancy at birth. Weekly deaths. Education Alongside health, education is often considered as one of the most important services. Educational attainment. Employment rate of recent graduates. Labour market Employment provides, among other benefits, the opportunity to gain independence, financial security and a sense of belonging.
Employment rate. Unemployment rate. Daily internet users. Making use of the internet. Economic activities. Economy The central measure of economic output is gross domestic product GDP. Gross domestic product. Agriculture, industry and services. Nights spent. Developments between and Environment and natural resources. Air transport. Road safety. Environment The effects of certain phenomena — for example, the rapid disappearance of vast areas of forest — have contributed towards a growing awareness and recognition that land is a finite resource and its use constitutes one of the principal drivers of environmental change.
Share of forest area. Agriculture In , there were
0コメント