As mentioned in the introduction to this chapter, the first traces that we have of Homo sapiens come from modern-day Morocco and suggest that the first modern humans emerged sometime around 315,000 years ago. Homo sapiens, unlike other hominins, did not take long to become highly mobile, moving out of Africa more than 100,000 years ago.
The early hominins could not form large communities, as they had limited communication skills. They could utter simple commands and communicate with hand signals, but complex linguistic expression eluded them. This achievement was one of the last in the evolutionary process of becoming human; it did not occur until between 100,000 and 50,000 years ago. Many scholars view complex language as the critical ingredient in distinguishing human beings from other animals. It is this skill that made Homo sapiens “sapiens,” which is to say “wise” or “intelligent”—humans who could create culture. Creating language enabled humans to become modern humans.
Homo sapiens’s Precarious Beginnings and Migration
About 200,000 years ago, massive shifts in Africa’s climate and environment again put huge pressures on all types of plants and animals, including hominins. Between 60,000 and 10,000 years ago, temperatures dropped, plummeting 40°F below present-day averages. A sheet of ice 2.5 miles thick blanketed northern Europe and North America. With much of the earth’s water frozen in glaciers, the climate went dry. The Sahara and Kalahari Deserts expanded; Africa’s large tropical rain forests became isolated pockets. Many plant and animal species died out all across Afro-Eurasia. To make matters worse for Homo sapiens, about 73,000 years ago Mount Toba, in present-day Sumatra, erupted, spewing into the atmosphere an enormous quantity of volcanic ash, which created a global volcanic winter that lasted six full years. The hominin populations declined precipitously, and their new species, Homo sapiens, threatened to go extinct before it could get started. Only a few thousand survivors huddled together in what remained of the once-rich tropical rain forests of equatorial Africa—a fact that means that all 7 billion of us today descend from an incredibly small African core population. In these extremely cold and dry environments, what counted for survival was superior intelligence and extraordinary mobility, precisely the traits that Homo sapiens possessed in abundance.
The highlands of eastern Africa were one of the regions least affected by climate change, and it was there that this new bigger-brained, more dexterous, and more agile species of humans congregated. The Homo sapiens population rebounded from its environmental crisis more successfully than Homo erectus, and when members of the species began to move out of Africa and the two species encountered each other in the same places across the globe, Homo sapiens prevailed—in part because of their greater cognitive and language skills.
TABLE 1.2 | Migrations of Homo sapiens
SPECIES
TIME
Homo erectus leave Africa
c. 1.5 MILLION YEARS AGO
Homo sapiens leave Africa
c. 180,000 YEARS AGO
Homo sapiens migrate into Asia
c. 120,000 YEARS AGO
migrate into Australia
c. 60,000 YEARS AGO
migrate into Europe
c. 50,000 YEARS AGO
migrate into the Americas
c. 16,000 YEARS AGO
ANALYZING GLOBAL DEVELOPMENTS
The Age of the Universe and Human Evolution
Our universe is nearly 14 billion years old. Our sun, earth, and solar system appeared nearly 4.5 billion years ago, and the earliest life-forms on earth appeared 3.8 billion years ago. Hominins, however, appeared on the scene only about 7 million years ago, which represents not even 1 percent of the total time that the earth has existed. For a long time they were confined to the African landmass, where they learned to walk on two legs, devised simple tools, and perfected their use over time. Africa remained the homeland for many different hominin groups for nearly 5 million years before Homo erectus ventured out of the continent, moving into central Asia, East Asia, Southeast Asia, and Europe, though not into the Americas. There were probably other waves of hominin migrations out of Africa, but the most important of the migrations out of Africa occurred as early as 180,000 years ago, when modern humans, Homo sapiens, left the continent and, with amazing rapidity, occupied all the globe’s landmasses. (See Map 1.2 to trace the migrations of Homo erectus and Homo sapiens.)
QUESTIONS FOR ANALYSIS
How do we know the age of the universe and when and how hominins first appeared and their evolutionary patterns?
Why are hominins and Homo sapiens so late in the evolutionary cycle, and why did Homo sapiens prevail over other hominins?
In your opinion, which of the different families of hominins deserves the designation of the first humans—and why?
Why are scientists disinclined to see a straight-line evolution from the earliest hominins to modern humans?
Sources: Chris Scarre (ed.), The Human Past: World Prehistory and the Development of Human Societies (2005); Ian Tattersall, Masters of the Planet: The Search for Our Human Origins (Palgrave Macmillan, 2012).
THE GLOBAL VIEW
MAP 1.2 | Early Migrations: Out of Africa
Hominin species, like Homo erectus, began migrating out of Africa hundreds of thousands of years before the present (BP), but only Homo sapiens went to all major inhabitable regions.
According to this map, when and to what regions did Homo erectus migrate? Homo neanderthalensis? Homo sapiens? Compare the location, extent, and dates of each species’ migration.
Locate the extent of ice sheets and identify the differences in exposed landmasses, as compared to modern shorelines. How did ice sheets and exposed land shape each species’ migration patterns?
Examine the dates for human settlement of the Americas. What do these dates suggest about human migration in the Americas?
The Homo sapiens newcomers followed the trails blazed by earlier migrants from Africa. (See Map 1.2 and Table 1.2.) Evidence, including part of a fossilized jaw with teeth, from a cave on Mount Carmel in Israel indicates that Homo sapiens were living there as early as 180,000 years ago. Whether that evidence suggests significant migrations or more limited forays by Homo sapiens is still unclear. Nevertheless, it is clear that from 120,000 to 50,000 years ago, Homo sapiens were moving in larger numbers into the same areas as their genetic cousins, reaching across Southwest Asia and from there into central Asia—but not into Europe. They flourished and reproduced. By 30,000 years ago, the population of Homo sapiens had grown to about 300,000. Between 60,000 and 12,000 years ago, these modern humans were surging into areas tens of thousands of miles from the Rift Valley and the Ethiopian highlands of Africa. (See Analyzing Global Developments: The Age of the Universe and Human Evolution.) In the area of present-day China, they were thriving and creating distinct regional cultures. Consider Shandingdong Man, a Homo sapiens male whose fossil remains and relics date to about 18,000 years ago. His physical characteristics were closer to those of modern humans, and he had a similar brain size. His stone tools, which included choppers and scrapers for preparing food, were similar to those of the Homo erectus Peking Man. His bone needles, however, were the first stitching tools of their kind found in China, and they indicate the making of garments. Some of the needles measure a little over an inch in length and have small holes drilled in them. Shandingdong Man also buried his dead. In fact, a tomb of grave goods includes ornaments suggesting the development of aesthetic tastes and religious beliefs.
Homo sapiens populations were also migrating into the northeastern fringe of East Asia. In the frigid climate there, they learned to follow herds of large Siberian grazing animals. The bones and dung of mastodons, large-tusked mammals, made decent fuel and good building material. Pursuing their prey eastward as the herds sought pastures in the steppes (treeless grasslands) and marshes, these groups migrated across the ice to Japan. Archaeologists have discovered a woolly mammoth fossil in the colder north of Japan, for example, and an elephant fossil in the warmer south. Elephants, in particular, roamed the warmer parts of inner Eurasia.
About 30,000 years ago, Homo sapiens began edging into the weedy landmass that linked Siberia and North America (which hominins had not populated). This thousand-mile-long land bridge, later called Beringia, must have seemed like an extension of familiar steppe-land terrain, and these individuals lived isolated lives there on a broad and (at the time) warm plain for thousands of years before beginning to migrate into North America. The first migrations occurred around 16,000 years ago, by foot and by boat. Modern humans poured eastward and southward into North America. A final migration occurred about 8,000 years ago by boat, since by then the land bridge had disappeared under the sea. (See Map 1.2 for evidence that demonstrates the complex picture of the peopling of the Americas, both along the western coastline and to the east.)
Using their ability to adapt to new environments and to innovate, these expansionist migrants, who were the first discoverers of America, began to fill up the landmasses. They found ample prey in the herds of woolly mammoths, caribou, giant sloths (weighing nearly 3 tons), and 200-pound beavers. But the explorers could also themselves be prey, for they encountered saber-toothed tigers, long-legged eagles, and giant bears that moved faster than horses. The melting of the glaciers about 8,000 years ago and the resulting disappearance of the land bridge eventually cut off the first Americans from their Afro-Eurasian origins. Thereafter, the Americas became a world apart from Afro-Eurasia.
Cro-Magnons (Homo sapiens) Replace Neanderthals
Homo sapiens spread out and occupied habitats where earlier hominin migrants had dwelled. From the time they left Africa, they migrated over the whole globe. By 25,000 years ago, as DNA analysis reveals, all genetic cousins to Homo sapiens were extinct, leaving only modern humans’ ancestors to populate the world. Neanderthals, members of an early wave of hominins from Africa, had settled in western Afro-Eurasia (ranging from present-day Uzbekistan and Iraq to Spain) perhaps 150,000 years ago. They were there well before Homo sapiens. Therein lies a tale, for scholars have had a long fascination with these hominins.
The Physical Evolution of Hominins.These three figures show the femur bones of Lucy, Orrorin tugenensis (one of the earliest of the hominins, who may have existed around 6 million years ago), and Homo sapiens. Homo sapiens have a larger femur bone and are bigger than Lucy—a representative of the hominin species Australopithecus afarensis —but have the same bone structure. Particularly useful indicators for determining differences among human ancestors are skull size (which can indicate the size of the brain and thus cognitive ability), the position at the base of the skull where the spine enters the cranium (which can indicate bipedalism), jawbones and teeth (which can indicate the kind of food they could have chewed), femur bones (which can indicate overall size and manner of walking), and foot and hand structure (which can indicate the kind of activities they performed).
For a long time, many scholars believed that Neanderthals were the primary precursors of modern-day Europeans. We now know that this is not true. The first knowledge of Neanderthals came with the discovery in 1856 of a skull in the Neander Valley of present-day Germany (the thal or tal in their name is the German word for “valley”). Some authorities wondered if the skull represented the so-called missing link between apes and humans. Not only did Neanderthals have big brains, but they also used tools, buried their dead, hunted, and lived in rock-shelters and caves. To judge from their behavior, their brain structure was not as complex as that of modern humans, so their cognitive abilities were far more limited than those of Homo sapiens, especially in their perception and creation of symbols. Neanderthals eventually gave way to Cro-Magnon peoples, a group of Homo sapiens named after fossil discoveries made in 1868 at a rock-shelter called Cro-Magnon in France. Although Neanderthal and Cro-Magnon communities overlapped in Europe for thousands of years and recent genetic evidence shows that there was some interbreeding from 50,000 to 60,000 years ago, the Neanderthals were not as well equipped to survive as the Cro-Magnons, who were truly modern humans. The Neanderthals’ short arms and legs and bulky torso may have made them stronger than Cro-Magnon men and women, but the Neanderthals were awkward and clumsy. The Cro-Magnons had the advantages of physical dexterity and high intelligence; the latter attribute gave them cognitive skills, language abilities, and a capability to see their environment in symbolic ways that Neanderthals did not possess. Ultimately, the Neanderthals left their genetic mark on modern humanity: 2 percent of the genome of people of non-African descent is Neanderthal DNA. Cro-Magnon Homo sapiens replaced Neanderthals in Europe between 45,000 and 35,000 years ago.
In 2008, Russian archaeologists dug up a pinky bone at the Denisova Cave in the Altai Mountains of southern Siberia and thereby discovered another hominin group that had many of the characteristics of Homo sapiens. These hominins, who looked different from Homo sapiens, had lived in this cave off and on from 287,000 years ago. They even shared a common ancestor with the Neanderthals about 400,000 years ago and interbred with the Neanderthals and our own species, as indicated by DNA drawn from living peoples in East Asia, Australia, the Pacific Islands, and the Americas. Some scientists have suggested that the interbreeding of Homo sapiens with the Denisovans enabled modern humans to survive in the Tibetan highlands at altitudes of close to 11,000 feet and as early as 15,000 years ago. Using aDNA drawn from Denisovan remains, scientists have reconstructed their body types, noting that they had massive brain cases and giant molars as well as larger neck vertebrae, thicker ribs, and a higher bone density than modern humans. They may have weighed well over 200 pounds and were robust and very large individuals. One investigator observed that they would have done well as modern-day football players. Advances in aDNA technology may allow researchers to identify previously unclassified remains as Denisovans. Scholars’ understanding of this recent hominin relative, genetically distinct from Neanderthals and modern humans, is only beginning to take form.
Neanderthal (left) and Cro-Magnon (right) Skulls.These two skulls show that Neanderthals had a large brain capacity and a larger head than modern humans. However, Neanderthals lost out to Homo sapiens in the struggle to survive as Homo sapiens spread across the globe.
The first humans; emerged in Africa as early as 300,000 years ago and migrated out of Africa beginning about 180,000 years ago. They had bigger brains and greater dexterity than previous hominin species, whom they eventually eclipsed.
