The Paleolithic age in the Pleistocene epoch of prehistory begins with the first use of manufactured tools by hominids and ends with the thaw of the last ice age (leading into the Mesolithic and the Neolithic age with the advent of agriculture). Its exact duration varies from place to place and from hominid group to hominid group.
Divided into three sections—chronologically the Lower, Middle, and Upper Paleolithic (with the Epipaleolithic following this last in place of the Mesolithic in parts of the world without major glaciation)— our hard data on the Paleolithic is scant compared to the archaeological riches of the Neolithic. Most of what we know is inferred from fossil record, amplified by genetic research and art from the Upper Paleolithic.
The term hominid refers to members of the Hominidae family of primates, including all humans, chimpanzees, gorillas, and orangutans. The term human is more loaded and more controversial than hominid (or hominine for those hominids with a capacity for language and culture). According to paleontologist Richard Leakey, human refers to all bipedal hominids, which includes members of the genus Australopithecus and the genus Homo.
Bipedalism, or the ability to stand and walk upright, was a major change relative to the human ancestors and a significant alteration in structure. It was necessary for tool use, because it keeps two limbs free for other manipulation, although because of the several million year gap between bipedalism and tool use, there must have been some other initial benefit.
There are two leading theories, the first positing the ability to carry things while walking. Carrying may seem trivial at first, but consider the length of time that human children are helpless — compared to other species — and the gain to the species in being able to better protect those children.
The second theory privileges the energy efficiency of human bipedal locomotion. Although initial studies suggested that bipedalism is less efficient than quadrupedalism, this is true only when comparing bipeds to quadrupeds like cats, dogs, and horses—species that have evolved to make their quadrupedal motion as efficient as possible.
Tool Usage and Brain Size
There are four stages of human prehistory, the first of which is the evolution of that first human species—the bipedal ape descendant—7 million years ago. The second is the adaptive radiation of these early humans.
Adaptive radiation is a biological term to describe the rapid creation of new species following a radical change in environment or ability, in this case the gains of bipedalism. With the third stage, the Homo genus arose from this speciation with a considerable increase in brain size.
Homo erectus dates to 2 million years ago, and its predecessor, Homo habilis (who some researchers would classify as an australopithecine) dates to 500,000 years before that. The final stage is the arrival of modern humans: imaginative, innovative, artistic, language-using hominines.
Not every human species is an ancestor of modern humans; in fact, on the human family tree most are cousins or uncles. The most significant to the Paleolithic age are the Homo species. The smaller-brained australopithecines, despite their bipedalism, lacked a significant modern human feature: the two vertical canals in the inner ear are much smaller in Australopithecus and prehuman hominids than in the Homo genus.
It is thought that those canals may contribute to upright balance in bipedal locomotion, and while we know from fossilized footprints and the structure of the Australopithecus pelvis that he must have been bipedal, he may have been less steady on his feet.
Australopithecus was not a toolmaker, though Australopithecus robustus had the manual dexterity required. Non-Homo hominids lacked the mental capacity to conceive of tools and manufacture them, but they probably used them opportunistically—as chimpanzees can learn to use keys, for instance. Tool use only flourished in the Homo genus.
Homo habilis was probably the progenitor of the genus, descended from one of the australopithecines. Although his cranial capacity—and the surmised size of his brain—was half as large as the australopithecines’, it is still less than half that of modern humans’, and some researchers are reluctant to include habilis in the genus, preferring to see him as the last of the australopithecines.
Habilis’s arms were unusually long—like an australopithecine’s—and his hips were wider. His increased brain size was enough to master the manufacture of stone tools. Tools allowed habilis to rely on meat as a larger part of his diet—an enormous metabolic and evolutionary benefit. A less specialized, more flexible diet allows a species to prosper in more environments and through more climatic changes.
Habilis was an Olduwan tool user. The Olduwan industry is named for the Olduvai Gorge in modern-day Tanzania. In an archaeological context an industry refers to a related group of artifacts and the processes directly related to them—not to the people, their other practices and behaviors, or their species. (Thus habilis was an Olduwan user, but Olduwan users are not by definition Homo habilis.)
The Olduwan industry is found in eastern and southern Africa as well as Europe—where a Homo erectus group brought it. Olduwan tools were nearly always right-handed. Lateralization—the unequal distribution of skill and tasks between the right and left hand—developed in the Homo genus and possibly in Australopithecus.
Lateralization is an evolutionary puzzle, not simply because of the question of what benefit hand specialization has, but because left-handedness has existed in a minority of the population for so long that there must be a reason for its genetic preservation.
The basic method of the Olduwan industry was to strike an appropriate stone (such as obsidian or chalcedony) with another stone, called a hammer stone, which fit easily into the hand and was sufficiently hard (such as quartz).
The blow would produce flakes, and the cone of force from the blow made for easily controlled fractures to give the flakes sharp cutting edges—sharp enough to cut through animal hide or saw through tendons, the fundamental tasks of early cutting tools.
Acheulean and Clactonian Industries
The Olduwan industry developed into the Acheulean and Clactonian industries, and the groups had contact with each other. Acheulean toolmakers refined Olduwan methods by using pieces of wood and bone to trim flakes through pressure instead of repeated hammer stone strikes, allowing the creation of cutting edges nearly as sharp as modern razorblades—and for the first handaxes, made from the sharpened core the flakes left behind.
While the Olduwan industry was barely advanced from opportunism, consisting in crude terms of broken rocks, the Acheulean required advanced planning and intent—the province of the larger-brained Homo erectus.
The Homo Species
Of the many Homo species that existed, seven other than habilis and sapiens (modern humans) are worth examining:
Homo rudolfensis is attested in only one specimen, a skull estimated to be 1.9 million years old. It may be a specimen of Homo habilis, an ancestor, or a sibling also descended from the australopithecines, but this uncertainty demonstrates that our knowledge of the human family tree is probably full of gaps that future discoveries may fill.
Homo erectus was once believed to be the oldest member of the genus but remains significant not only because of its considerable cranial capacity but because it is responsible for much of humankind’s migration.
Erectus settled in much of Africa and Southeast Asia, spreading its tool industries (Olduwan and Acheulean). Erectus was probably the first species to exhibit social behavior similar to modern humans’, and he may have abandoned habilis’s scavenging to become a full-fledged hunter-gatherer.
He would not have been capable of complex speech: If he had a language, his vocal system would have limited it to simple sounds. Erectus is the common ancestor of Homo floresiensis, Homo neanderthalensis, and Homo sapiens, and a relation of some sort to Homo ergaster.
Homo ergaster is probably a child of erectus. Although some believe ergaster came first, he has a larger cranial capacity and generally more modern features. The fossils found with ergaster remains suggest that he was an Acheulean tool user and had mastered fire, perhaps using it to cook food.
Homo antecessor is among the oldest human remains found in Europe and was probably the child of erectus and an ancestor of both Homo sapiens and Homo neanderthalensis: It is widely believed to be either the parent of Homo heidelbergensis or a specimen of that species, and sapiens to be either its child or grandchild. Antecessor remains have been found with manmade cuts in the bone, which could indicate either cannibalism or interspecies predation among different Homo species.
Homo heidelbergensis is the parent of Homo neanderthalensis. Though little is known of it beyond its Acheulean tool use, it may have been the first to bury its dead, and if the genus had not already developed a capacity for language with erectus, heidelbergensis may have been the first to do so.
Homo neanderthalensis is popularly known as Neanderthal Man and lived for some 200,000 years, dying off 29,000 years ago, making it one of the last relatives of modern humans. Slightly shorter, stouter, and more barrel-chested than modern humans, neanderthalensis had a larger cranial capacity and probably a bigger brain.
He was part of the Mousterian industry, with a heavy reliance on bone, horn, and wood implements for shaping flakes—and preferred working with wood and bone over stone. Since neanderthalensis lived in a cold climate and through part of the last ice age, these organic materials may have been more practical than flint and obsidian, which become brittle and splinter in cold temperatures.
Neanderthalensis may have possessed human speech: Given the shape of his larynx and the position of the tongue, it would have been higher pitched and more nasal than the modern human voice. There’s considerable evidence that he buried his dead, but whether this had any religious significance is a matter of speculation.
Until very recently neanderthalensis was believed to be the last living member of the Homo genus other than Homo sapiens—our only cousin or sibling. In the 21st century Homo floresiensis remains were discovered on the Indonesian island of Flores, where island speciation had resulted in the development of giant lizards, dwarf elephants, and other creatures of atypical size. Floresiensis, which died out only 12,000 years ago in the Neolithic, was a furry dwarf with long arms and small brain, at the low range of chimpanzee brain size.
His cranial capacity is small enough to warrant debate about whether he qualifies as a Homo or Australopithecus, but with such a late date there can be little doubt of his Homo parentage through some child of erectus. It is too soon to predict how this will change our models of prehistoric man.
Modern humans—the species Homo sapiens—developed in the Middle Paleolithic period, a time also marked by the mastery of fire by human species, the evolution of neanderthalensis, and most likely the use of fire to smoke and preserve meat.
Homo sapiens had a greater cranial capacity than any species other than neanderthalensis, and it may have been luck that preserved sapiens while his neanderthalensis cousin perished: Both were expert toolmakers, and both were well adapted to many environments. Sapiens developed in Africa, and there are two competing theories to explain how the species populated the rest of the world.
The Origin of Modern Humans
One theory is the "out of Africa" hypothesis, also known as the "Eden" hypothesis or single-origin hypothesis, which stipulates that all Homo sapiens stem from a common ancestral group that began in Africa and migrated elsewhere, perhaps following the migratory patterns of erectus (even while displacing that ancestor species).
The multiregional origin hypothesis, in contrast, proposes that different ethnic groups of Homo sapiens developed from different groups of Homo erectus and did so independently. Supporters of this hypothesis believe that, facing similar evolutionary needs, sapiens would be the inevitable evolutionary end of erectus and that no common ancestor group is needed to explain the presence of Homo sapiens in so many different environments.
While some fossil evidence can be used in support of the multiregional hypothesis, and the discovery of Homo floresiensis at least demonstrates that non-sapiens species of the Homo genus persisted very late into prehistory, molecular data increasingly supports the single-origin hypothesis.
Regionalization and Language
During the Upper Paleolithic—about 40,000 years ago—regional cultures developed, with hunter-gatherers organizing into groups with stronger ethnic ties. Generally such groups would be composed of bands of about 20 to 25 family members, with 20 bands associating together in a loose tribe. Ethnic identity—the idea of associating with these tribal members, or a related tribe, even without direct family ties—began to develop.
Bone and horn were adopted as toolmaking materials, making for better darts, spears, and harpoons; barbed fish hooks and toothed tools (like primitive saws) were developed. It was also during this last stage that humans migrated to Australia (about 50,000 years ago) and the Americas (25,000 years ago).
Language may date to the Upper Paleolithic, but researchers are at odds over the question of whether a human species with the capacity of speech could have existed without developing language.
There is no evidence of language use in the Middle Paleolithic, and arguments for it depend on the biological fact that the speech organs existed and the notion that advanced tool use and hunting would not have been possible without advanced communication among members of the group.
By the Upper Paleolithic it is highly likely that language had developed. Primitive art emerges at this time: the so-called Venus figurines, the first of which (made of stone, not ceramic like the Upper Paleolithic examples) actually appear in the Middle Paleolithic. Venus figurines were small, crude figurines of women with prominent stomachs from pregnancy or obesity.
They have been the subject of much speculation, particularly in the area of prehistoric religion and magic: They may have been symbols of fertility or portraits of a mother goddess. Some researchers have used them to support a theory that early cultures were religious and/or socially matriarchal.
Another figurine from the middle of the Upper Paleolithic, found in a German cave, shows a statue of a lion man similar in style to various French cave paintings. The craftsmanship is extremely sophisticated compared to the abstraction of the Venus figurines, with facial details and incised strokes to represent fur.
The Paleolithic ended with the coming of the ice age in those parts of the world where glaciation occurred and the coming of agriculture. The Mesolithic in glaciated areas and the Epipaleolithic in the rest of the world, transitional periods leading to the Neolithic immediately prior to "early history", followed.