[Originally presented at the Bonkworld Lecture Series, August 16, 2000. Most of the content and all of the quoted material below has been culled from John Reader's "Africa: A Biography of the Continent."]
My lecture today will be very simple. I would mainly like to provide a sense of temporal perspective regarding the world and our place as humans in it. Everything we know of modern human history, by which I mean recorded history--the last 5 thousand years or so-- is essentially completely insignificant in terms of time, not only by comparison to the history of the planet or the universe, but also just by comparison to the history of human evolution. I'd like to do three things here this evening: 1) give a broad overview of the bare facts of evolution; 2) explain some of the likely driving forces behind our evolution; and 3) note a lesson or two from history that may be instructive for our future development.
I believe it is a worthwhile thing to develop and maintain a good sense of perspective so that we can appreciate the reality of our present situation as a species on the planet more accurately, and, if I may say so, more humbly. We like to think of ourselves as a highly successful species, having taken over the entire world and all. Yet the fact is that our catalog of accomplishments, and indeed our whole history as Homo sapiens, at some 130,000 years, pales beside the record of Homo Erectus, who kept going for 1 million, 400 thousand years, or Australopithecus, who enjoyed a solid 3 million years of success as a species.
Therefore I hope I can help to inspire a measure of awe and humility, and a recognition that our development thus far has been far from inevitable, and our continued survival far from assured. We are thus far only a tiny blip on the radar screen of primate evolution, and I daresay if we hope to create a record approaching that of our distinguished ancestors, we are going to have to change a few things about the way we do business.
Having said that, I think that the general outlines of human evolution show a distinct trend towards constant improvement. We've gotten steadily taller, less hairy, and brainier as time has progressed; indeed, I think it is indisputable that human evolution has conspired to make us increasingly sexy motherfuckers. I'd like to turn now to Figure 1, which suggests in broad strokes the outlines of this transformation.
Now I'd like to turn to Figures 2 and 3 to try to give a better sense of the time frame we're talking about.
Almost all of this evolution occurred on a single, joined land mass known as Pangaea--the continents had not yet "drifted" apart to their current positions. Africa was still joined to Eurasia and North America until 120 million years ago, and to South America until 100 million years ago.
Many primate fossils have been found in Europe and North America from 65 to 40 million years ago, and very few in Africa, yet chimps and hominids definitely evolved only in Africa. Therefore the older African primate fossils have either not been found yet, or the primates moved into Africa from elsewhere.
Modern primates -- opposable thumbs, nails instead of claws, teeth for eating leaves and fruit instead of insects -- appeared 35 to 40 million years ago. The earliest undisputed higher primate is Aegyptopithecus, from 35 million years ago, found in Egypt. It was the size of a cat, quadruped, and had a large brain for a mammal of that time.
After Aegyptopithecus, 18 million years pass before the fossil record gives us another glimpse of primate evolutionary history: Proconsul, found near Kenya, dates from 17 million years ago. It was the size of a baboon, quadruped, tree-dwelling, fruit-eating. It had the backbone of a gibbon, the shoulder and elbow joints of a chimp, the wrists of a monkey. It was unlike any living ape, and could well be the common ancestor of them all, including humans.
The evolutionary trail continues from there to Kenyapithecus, at 15 million years ago, and then an extraordinary thing happens: There is a ten million year gap in the fossil record! This is the "hidden epoch" of human evolution. Then suddenly at about 4 million years ago we have Australopithecus, with its upright stance and bipedal gait. The fossil record in between is almost entirely nonexistent.
"It is as though a magician had drawn a veil over the process, ushered a shuffling arboreal primate behind one end of the veil, and called forth the bipedal ancestor of humanity from the other."
One of the most important questions about human evolution is which came first, bipedalism or the large brain? Darwin felt it was bipedalism, but many others argued it must have been the large brain. In 1912 we had the discovery of Piltdown Man, which seemed to settle the question in favor of large brain. However, it was proven a fake in 1953! This fake stifled further intellectual inquiry on the matter for over 40 years! By that time stone tools were acknowledged as forerunners of modern technology, and in the aftermath of WWII the "killer ape" theory as championed by Raymond Dart emerged, which was based on simultaneous development of bipedalism and brain.
"[Early man] seized living quarries by violence, battered them to death, tore apart their broken bodies, dismembered them limb from limb, slaking their ravenous thirst with the hot blood of victims and greedily devouring livid writhing flesh. The loathsome cruelty of mankind to man forms one of his inescapable, characteristic, and differentiative features; and is explicable only in terms of his carnivorous and cannibalistic origin...The blood-bespattered, slaughter-gutted archives of history from the earliest Egyptian and Sumerian records to the most recent atrocities of the Second World War proclaim this mark of Cain that separates man from his anthropoidal relatives and allies him rather with the deadliest of the Carnivora."
This was controversial stuff, as many others felt that cooperation rather than competition was the best way to ensure the survival of our species, and the debate raged on until the 1970s when definitive proof arrived with the discovery of some key fossil evidence. Bipedal fossils were found in Ethiopia dating from 3.2 million years ago, while the earliest stone tools date from about 2.4 million years ago. That was Australopithecus afarensis, better known as Lucy. Lucy would have weighed about 30 kg (65 lbs) and been "barely tall enough to peek over a garden fence" at just over a meter in height. She had long arms, indicating that she was still a good little tree climber although she was very clearly bipedal. Thus bipedalism preceded stone tools by well over a million years, and a substantial increase in brain size occurred 700,000 years after the first stone tools.
Bipedalism is a highly inefficient form of locomotion. "In terms of the energy required to move proportionately equal units of body mass over given distances, humans are not much more efficient than penguins." Chimps use much less energy to get around, and they're also faster and more agile. Bipedalism required major skeletal and muscular adaptations, which occurred relatively rapidly, thus the selection pressure must have been intense and the benefits outweighing the drawbacks.
Several factors are most likely to have contributed to the development of bipedalism. First, there was an ecological niche to be filled related to the migrating herds of antelopes and wildebeest. Carnivores fed well while the herds came through, but then suffered lean times when they left; their young grew slowly, so they couldn't keep up continually with the migrating herds. Bipedalism and not dwelling in trees would have provided an advantage in keeping up with the herds and scavenging for food. Also, it adds to security, since they didn't stay in one place long enough to lure predators.
Also, being upright has great advantages as a cooling system, which would have been a major benefit not only in scavenging and gathering on the hot savannah, but also would have helped to enable the development of a large brain over time--the brain is a disproportionately large user of energy and requires the greatest amount of cooling.
Some comparisons among the major strains of hominids to have evolved:
Evolutionary studies sometimes have political implications, as we search for relics that describe how societies seem to have operated. Normally when archeologists look for evidence of civilizations they look for citadels and evidence of what would be the equivalent of urban societies, with social hierarchies and centralized authority. Evidence from Jenne-Jeno (Niger delta, West Africa) suggests a civilization that lasted for some 1,600 years, highly socially evolved but with no centralized authority or system of hierarchy, i.e., an egalitarian, communitarian society that was very successful for a very long time (by modern standards).
"They settled within shouting distance of each other, but avoided assimilation into a single urban entity. With none of the centralized authority that elsewhere controlled the social tensions generated by the emergence of urbanism, clustering allowed a diverse population to congregate for economies of scale, and to draw upon the services of other specialists without surrendering their independent identities, the whole thereby functioning as a city, and providing a variety of services and products to a wider hinterland. In effect, the push of specialization produced occupational castes and ethnic distinction, while the pull of economic integration produced a web of shared myth and belief that emphasized both individual ethnic identity and mutual interdependence."
Long-distance trade is what broke the model of localized self-sufficiency. The first commodity traded over long distances was salt. Wherever people have developed a taste for salt, they consume more than their physiological requirement. Sources of salt in Africa were not distributed for the convenience of human populations; thus, traders found a reason for being. Later, other goods such as kola nuts also became widely traded. Large amounts of individual wealth were for the first time made possible, and extreme inequality began insidiously to weave itself into the very fabric of society.
"A vertical stratification of society came into being, creating sharp discontinuities in the horizontal layer of age-based authority that previously had restrained individual ambition. Some people became more equal than others, controlling rather than sharing resources. Once the trend had begun, resources inevitably fell under the control of fewer and fewer individuals, culminating in the centralization of authority and the exercise of coercive power by a ruling elite. Power was exercised most coercively by traders who sold the porters as well as the goods they had carried to distant markets" (the beginnings of a slave trade)
We are going faster than ever before, but if we look at history we must understand that we have ruled for only the briefest of times. At the pace we are going, we need to be extremely careful about how we organize ourselves, how we utilize and share our resources, and how we manage the planet upon which we depend for our very existence. These circumstances demand humility, and history gives us no shortage of instructive examples from which we can learn. Arrogance will surely lead us to disaster.
Humanity! Evolution! History! It's all ridiculously interesting, and here's a fun-filled, all-too-rare excuse for the ordinary working person to think about it for a few minutes. Here it is, courtesy of Bonkworld, for the first time ever, the amazing Early Man Quiz! But be careful--it's a pretty tough one!
(All facts derived from Africa: A Biography of the Continent by John Reader [New York: Vintage Books, 1997])