Today's lecture: a quick survey of human origins.
My purpose is, first, to supply a general background, and second, to take a preliminary look at a vexing question: what makes our period, the historic period, the period of civilization, so different from most of the long time that humans have existed?
The story of human origins has been extensively rewritten since WWII; in fact, there has been a tremendous amount of activity since 1980. Archaeologists have found new material, used new techniques, and propounded new theories that indicate that the story of our species' evolution is longer and more complicated than almost anyone thought when I was a kid. One of the most interesting things to emerge from this work is the idea that Africa is probably the place where most human evolution occurred. Darwin believed this; more recent scholars have proved his hypothesis correct.
The evidence on which the new theories is based is very sparse. Paleoanthropologists, the specialists in human origins, work like historians from fragmentary evidence -- fragments of fossilized bone, usually skull bones. Finding evidence is a matter of luck. According to Donald Johanson, a very lucky paleoanthropologist, "quite a few distinguished paleoanthropologists have gone a lifetime without finding a single [fossil]" (Lucy, 15). Interpreting finds involves a great deal of interpolation -- in other words, informed guesswork. Every new find may be another individual of an identified ape or human species, or it may be evidence of a completely new species. And different paleoanthropologists will have different opinions on the significance of any given find. An accumulation of new data will always spark a heated debate on what the human family tree looks like.
The situation is complicated even more by the fact that human evolution is now being investigated not only through the examination of fossil remains, but through molecular biology -- something discussed at some length by David Christian. Scientists are looking at human and ape genes, to see how they are alike and how different, and trying to detect when our genetic material diverged from that of gorillas and chimpanzees, our closest relatives. The molecular biologists' chronology of human evolution often disagrees with the chronologies constructed by paleoanthropologists, who are basically specialists in old bones and ancient anatomy. These kind of disagreements have no simple solutions.
I am no expert on any of this material, and include it in the course for much the same reason that David Christian discussed cosmology, geology and human evolution in Maps of Time: because I think a big perspective is useful in history, and especially in ancient history. Christian has been one of my sources for this lecture, but I've also looked at writings by Richard Leakey and Donald Johansen, two major scholars in this area. I also must credit Washington State University's on-line study module The Long Foreground: Human Prehistory, which, brief as it is, covers the subject in more detail than this lecture does.
To begin: One thing that experts do seem to agree on is that at most times we know of, there were a variety human and near-human species co-existing on earth. It's only recently that there has only existed a single human subspecies, homo sapiens sapiens, that's us. The norm has been co-existence and presumably competition. The discovery in 2004 of a "hobbit-sized" human species called homo floresiensis from its home on the Indonesian island of Flores underlines this fact. When the Flores people lived there, between 95,000 and 13,000 years ago, humans of our species had been around for at least 35,000 years, and for most of that time Neanderthal humans were living in Europe. That gives us three human species in what are, for paleoanthropologists, very recent times indeed.
We will see, as we survey human evolution, that there are lots of species and no one is completely sure how they relate to each other.
It's generally agreed -- and backed up by increasingly sophisticated genetic analysis, that humans and their ancestors are related to apes. Our closest cousins are the "great apes," the gibbons, the orangutans, the gorillas, the chimpanzees, and the bonobos (or pygmy chimpanzees). Of this group, the most closely related to us are gorillas and the chimpanzees, who share almost all our genetic material. Even so, the human line broke off from the chimpanzees (our very closest cousins) quite long time back. The "missing link," the species that has both human and non-human descendents, may be represented by "Millenium Man," a find discovered in 2000, the remains an individual who lived perhaps 6 million years ago.
It's possible, then, that humans and their closest extinct relatives have evolved separately for 6 million years.
It's time to say something about "extinct human relatives." The most important class of them who are not considered humans are a group of species designated Australopithecines, "southern apes" or "southern near-humans." What makes them "near-humans" and what makes them "non-humans?
The answer to the first question seems to be that "walking on two feet most of the time," or "bipedalism," is what distinguishes all us hominids (humans and australopithecines taken together. Other great apes don't walk efficiently, and have more of the characteristics of other apes of the past and present that makes them happiest living in trees. We homo sapiens sapiens, other humans, and australopithecines are animals that for some reason decided a different form of locomotion was some kind of advantage. As David Christian points out, scholars still argue about what the advantages were. Whatever they were, numerous species decided to exploit this evolutionary tactic of bipedalism.
What makes australopithecines different from humans? Though australopithecines had big brains on the ape scale, and some appear to have used tools, it is unlikely that they had any kind of developed language. The human line includes the hominids that slowly developed the habit and talent of using tools, grew bigger brains, and brains of a sort that -- as comparative anatomy indicates -- included those features associated with human linguistic ability.
There were robust, strong australopithecines, and more slender sorts. The more slender sorts seem to include our ancestors.
Australopithecines, taken as a group, were bigger than their ancestors, 120 to 150 cm (4 to 5 ft.) tall, walked erect quite easily, and had bigger brains than any preceding ape..
Human brains today range in size from 1000 cc to 1800 cc, depending mainly on body size and not on intelligence. The australopithecines had brains in the 400 cc range.
Two australopithecines worthy of note are a. ramidus, the earliest "bipedal" species (exised as far back as 4.4 million years ago) and a. afarensis (lived between 4 million years ago and 2.7 million years ago). The most famous a. afarensis is the individual known as "Lucy," discovered in 1974. Lucy's remains include much more of her skeleton than most finds (skulls are more easily preserved and interpreted), and Johansen, her discoverer, was very impressed by her human-like pelvis and legs, which allowed her to walk and stand like people today. Nonetheless there are some significant differences. Her arms had the proportions of a chimp, not a human, and brain size and shape don't indicate linguistic ability. It's unlikely that a. afarensis used tools.
It is unclear whether Lucy's people were among our ancestors, or only of later "robust" australopithecines.
Beings accepted as human finally appearat about 2.2 million years B.C. This is where homo habilis, or "handy-man" has been detected. Handy-man indicates a talent with tools. Homo habilis was probably not the first to make tools. Modern chimps and some other great apes use tools occasionally. However, h.h. seems to have been the first to make tools as a matter of course. The tools were just pebbles roughly chipped to make an edge, but were made on a regular basis. The primitiveness of the stone tools may deceive us. After all, anything more perishable is gone without a trace. Many useful things might have been made from skin or fiber.
On the other hand, homo habilis' talent with tools only went so far: once they had mastered the chipped pebbles known as Oldowan tool, they ceased to develop them. Oldowan tools were used up to 250,000 years ago -- for about 2 million years straight -- by h.h. and other early humans.
Homo habilis was much smarter than any non-human animal we know of, but had brains quite a bit smaller than ours. H.h. brains were around the 650 cc mark. H.h., who lived only in Africa, also did not look much like us.
According to Johansen, put H.h. on the subway "and people would probably move to the other end of the car (Lucy, 20)."
H.h. was quickly succeeded by homo erectus, a human who walked erect (an old and now deceptive name: homo erectus was not the first erect early human). A bigger brain (700 to 1250 cc, overlapping the modern human range), a more modern face and jaw. H.e. could ride around the Toronto subways with only suspicion that he or she was different. H.e. was a human with a real talent for tool making, and the species lasted a good long time. In fact, h. erectus was a contemporary of h. sapiens, h. sapiens sapiens, and homo Neanderthalis. For most of the time h. sapiens has existed, h. erectus has been around, too.
There is enough evidence to talk about h.e. social organization.
The basics: humans (as opposed to australopithecines) worked together in small tribes or big family groups to gather and share food. Most was still plant food, seeds, fruits, wild vegetables of various sorts. They also ate meat. Sometimes this was scavenged meat, or small rodents that could be caught by hand. Other times, meat was actually hunted. Early human beings were distinguished from their hominid, australopithecine ancestors and cousins by the fact that cooperation was a constant feature of their lives. Other hominids hunted for food individually, and seldom shared it. Humans brought back the goodies to a home base, a home base which was moved from time to time, and shared the food around.
This meant, of course, that humans communicated, planned, and worked together. We don't know how far back speech might be traced in the human line, but it was no accident: it was part of an evolutionary strategy that is basic to what we mean by humanness.
Early humans already showed sexual differentiation in their behavior. Both h.h. and h.e. had children that needed a lot of care after birth, years of care, provided mainly by their mothers, at least in the earliest stages. Mothers and small children stuck close to the home base of the group, and were responsible for much of the gathering of plant food. Adult males took the responsibility for hunting meat. Meat supplied far less than half of the food needs of the group, but, if modern human hunter-gatherers are anything like our remote ancestors, the meat was highly prized.
Homo erectus, though not identical with modern humans, should not be underestimated in intelligence or even in the richness of their existence. In the last few decades, research among modern hunter-gatherers has shown that life among so-called primitive tribes is not, as Thomas Hobbes said in the 17th century, "nasty, short, and brutish." It is not a matter of living and working on the brink of existence, of poverty, of near starvation, of always fearful of impending disaster which one is helpless to avert. If the climate is even half-way predictable, modern hunter-gatherers fulfill their basic needs in a short time. Usually they work about twenty hours a week or less, and spend the rest of the time loafing and socializing, both within the group and with their neighbors.
How important conflict is for modern hunter-gatherers (and by analogy h.e. and other early humans) is a matter of scholarly debate. For the last generation or so, many modern scholars impressed by the devastation caused by modern war have emphasized the small-scale, even ritualistic nature of fighting between hunter-gatherers. More recently, Laurence Keeley (War Before Civilization: The myth of the peaceful savage), using both historical and prehistoric evidence, has compared hunter-gatherer warfare to the nasty guerilla wars of more recent times, and emphasized the high proportional casualties that "small-scale" communities suffer in "small-scale" wars.
Modern hunter-gatherers are not in their own estimation poor. Many of them know about agriculture, but can't see why anyone would want to work as hard as a farmer must. Now modern hunter-gatherers are identical to us, and just as far from homo erectus physically and mentally, as farmers or citified people, but in their way of life are probably quite close to our very ancient ancestors. The disadvantage of this way of life is that a serious injury, even one that may heal in time, may finish an individual off. But this is not inevitable. Later humans, like Neanderthals, living much the same kind of life, can be proven to have supported disabled fellow tribesmen for years.
And there may have been more to the life than my sketch suggests. Though many modern hunter-gatherers loaf in their off time, a few work very hard at cultural pursuits. One group of Australian aboriginees put in all their spare time maintaining a ritual way of life that has no obvious practical purpose -- kind of like watching movies today, or playing video games. It is quite possible that homo erectus had a cultural or ritual life.
Homo erectus marks an important stage in human evolution. Hunting and more sophisticated tool making (as well as fire) became a routine part of existence, and these capabilities imply much for sheer intelligence and ability to cooperate. Homo erectus was very adaptable -- so adaptable that bands began to leave Africa about a million years ago.
The next stage of evolution toward modern humanity is the appearance of homo sapiens 400,000 years ago. One of the big questions that paleoanthropologists worry about is whether homo erectus evolved into homo sapiens in one area, in Africa, at a fairly recent time, or whether homo erectus populations all over Africa, Europe, and Asia evolved into h. sapiens at an earlier time. Regional anatomical differences between different h. erectus groups seem to be reflected in the modern humans in the same regions. They are fairly small differences, like shovel shaped incisor teeth which are more common in Asia than elsewhere. On the other hand, genetically all modern humans are so close that the later evolution in Africa, with modern humans migrating from there later, has strong support. We see here different kinds of evidence giving different answers.
The best guess at the moment is that modern human beings, homo sapiens and homo sapiens sapiens also emerged first in Africa and spread from there. This further evolution was almost entirely in the shape of the head and its contents. As the species evolved into modern humanity, the head was reshaped, brains got bigger, and more complex. Certainly the human talent for language increased during this process.
When homo sapiens appeared 400,000 years they began manifesting, or at least leaving traces of undoubtedly human behavior. One of these traces is the burial of human bodies by their fellows. One famous found burial of the past, dating back to 60,000 years ago, took place in the mountains of Iraq.
Much earlier, in a cave near Peking a half a million years ago, a number of dead people had their brains scooped out and eaten. This find has fueled the idea that humans are by nature violent and self-predatory. But the interesting thing about the brains eating is that the brains were extracted very carefully through a slow, careful enlargement of the hole by which the spinal cord enters the brain. In other words, it looks like ritual cannibalism, and might well be a sign of respect instead of malice.
There may well have been some big differences between various groups of h. sapiens. We know for a fact that between 130,000 to 30,000 years ago, there were besides h. floresiensis, two major groups, homo sapiens sapiens (our ancestors), and homo sapiens neanderthalis, which later group is named after the Neander valley (thal in German) where their remains were first found.
Neanderthal humans were genetically very close to us, and we may have Neanderthal ancestors. In some ways they would seem to have the advantage over modern humans: they were very strong, with major bones that were twice as thick as ours. They also on average had bigger brains. But although they were tool users, and had a cultural life, including burying the dead, it seems that they were not as adaptable as our ancestors. Their "tool kit" changed very little over the life of the species. Also, the parts of the brain associated with speech were not as well developed.
Homo sapiens sapiens, like h. s. neanderthalis a descendant of h. sapiens, is our own particular group, the species that dominates and maybe endangers the earth today. What makes h.s.s. special? Why was it able to eliminate all other hominids and many other species as well?
It is certainly not a matter of speed, strength or even sheer ferocity. It's not even a matter of brain size.
It seems to be a matter of speech and the ability to use symbols to store and communicate knowledge. This made it possible to create "cultures," that is ways of life that were not genetically determined, and which could therefore be changed and adapted.
For instance, Homo sapiens sapiens was an artist . Perhaps - earlier variants of human beings were, too, but the use of symbols by modern humans, genetically speaking, is extraordinary, well before agriculture or civilization were invented.
A few artifacts from the period of the last ice age, a few 10s
of thousands of years ago, have survived. These include:
Humans of this era were still hunter-gatherers, as their ancestors had been for eons. Whatever fads in tools or clothes or body-painting or religion or music that divided up their history, they are all lost to us. But the basic method of feeding oneself was the same -- food gathering, not food production.
The big turning point that separates most of us from all of them was the invention of agriculture, perhaps 10,000 B.C., 12,000 years ago. We do not know why some people felt it necessary or advantageous to start growing food in a regular and predictable way, instead of gathering what there was?
We will investigate this question next time.
We do know :
In the next lecture we will look at a couple of early agricultural settlements,
one hypothetical, the other quite real, to try to understand this great
revolution in human affairs, the Agricultural Revolution.
Richard E. Leakey and Roger Lewin, Origins: The Emergence and Evolution of Our Species and its Possible Future (New York, 1977; revised 1982).
Donald Johanson and Maitland Edey, Lucy: The Beginnings of Humankind (New York, 1982).
Donald Johanson and Blake Edgar, From Lucy to Language ( New York, 1996).
Marshall Sahlins, "The Original Affluent Society?" Stone Age Economics (1972).
Laurence H. Keeley War Before Civilization: The myth of the peaceful savage (New York, 1996).