Humans are so adaptable we have migrated to almost every part of the world and in the process forced the extinction of all other species of hominoids. We are the only species of hominoid left. About , years ago humans successfully migrated out of Africa. By about 50, years ago we were already beginning to diverge into distinct populations.
Our species evolved in Africa , years ago. The Genographic Project has found that people spread out of Africa in at least two migratory waves. The first wave travelled from eastern Africa into the area of the east coast of the Mediterranean known as the Levant about 80, years ago. The later second wave moved from Africa into the Arabian Peninsula and continued eastward following the coast of South Asia about 50, years ago. As of , humans had built so many dams that nearly six times as much water was held in storage as flowed freely in rivers.
FACT: From to , the population of cattle, pigs, sheep, and goats increased from 2. The number of domesticated fowl grew from 3 to 16 billion. FACT: Of the estimated 15, species of mammals and birds, only about 30—40 have been used for food. FACT: Between and , just 40 years, the human population doubled from 3 billion to 6 billion people. FACT: A child dies of malaria every 30 seconds. FACT: Every second someone in the world is infected with tuberculosis.
Skip to main content. Human Characteristics: Humans Change the World For millions of years all humans, early and modern alike, had to find their own food. By , years ago Modern humans collect and cook shellfish By , years ago Modern humans exchange resources over long distances By 90, years ago Modern humans make special tools for fishing Between 80, and 60, years ago Modern humans spread to Asia By 77, years ago Modern humans record information on objects About 74, years ago Near-extinction!
By 70, years ago Extinction! Homo antecessor in western Europe Atapuerca , Spain , closely related to the last common ancestor of Neanderthals, Denisovans and modern humans. Homo sapiens enter Eurasia Greece : first of multiple dispersals out of Africa by humans with early modern traits, including globular braincase and descended larynx facilitating spoken language. Hunter-gatherer nomads. Homo with mix of archaic-human and Neanderthal traits Nesher Ramla , Israel : stone-tool industry, cooking meat; cultural exchange with humans?
Eurasian Homo sapiens co-existing with Homo floresiensis soon extinct and Homo luzonensis , interbreeding with Neanderthals and Denisovans. Anatomically modern humans henceforth the only hominin. Both species had rituals—Neanderthals buried their dead—and both made ornaments and jewelry.
But the moderns produced their artifacts with a frequency and expertise that Neanderthals never matched. 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.
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