"Before the Dawn:
Recovering the Lost History of Our Ancestors"
(New York: Penguin Books, 2006)
1. Genetics & Genesis
3. First Words
“Like everything else in biology, the human past and present are incomprehensible except in the light of evolution.” p. 6
Chapter 1: GENETICS & GENESIS
There is a clear continuity between the ape world of 5 million years ago and the human world that emerged from it.
The thread is most visible at the level of DNA: the genomes of humans and chimpanzees are 99% identical. It is evident enough in the physical resemblances between the two species. But perhaps the most interesting level of continuity is between the social institutions of the ape and human worlds.
The apes ancestral to both chimpanzees and humans probably lived as small bands of related individuals who defended a home territory, often with lethal attacks against neighbors. They had separate male and female hierarchies and most infants were sired by the society's dominant male or his allies. The emerging human line was also territorial but in time developed a new social structure based on pair bonding, a stable relationship between a male and one or more females. This critical shift would have given all males a chance of reproduction and hence a stronger interest in the group's welfare, making human societies larger and more cohesive.” p. 7
A principle force in the shaping of human evolution has been the nature of human society
After splitting from the apes, those in the human line of descent evolved upright stature and developed dark skin in place of the ape's body hair. But the most significant change – a steady increase brain size – probably evolved in response to the most critical aspect of the environment, the society in which an individual lived. Judging whom to trust, forming alliances, keeping score of favors given and received – all were necessities made easier by greater cognitive ability. By 50,000 years ago, the social benefits of more efficient communication had prompted the evolution of a novel ability possessed by no other social species, the faculty of language.” p. 7
The human physical form was attained first, followed by continual evolution of human behavior.
Anatomically modern humans, people whose physical remains resemble the skeletons of people today, became common 100,000 years ago. But they showed no sign of of teh advanced behaviors that emerged 50,000 years later, probably made possible by the evolution of language. With this new faculty and the greater social cohesion, the first behaviorally modern humans were able to break out of Africa and displace the archaic humans like the Neanderthals who had left Africa many thousands of years previously. p. 8
Most of human prehistory occurred in, and was shaped by, the last ice age.
The adaptations for three principle social institutions, warfare, religion, and trade, had evolved by 50,000 years ago.
The ancestral people had a major limitation to overcome: they were too aggressive to live in settled communities
Early human societies lived as small bands of hunter-gatherers, their existence dominated by incessant warfare. For 35,000 years after leaving the ancestral homeland, these nomads were unable to settle down. Only gradually did humans evolve to become less aggressive. The tempo of warfare eased and a more gracile, or delicately boned, human form evolved in populations throughout the world. In the Near East, around 15,000 years ago, people at last accomplished a decisive social transition, the founding of the first settled communities. In place of the hunter-gatherers' egalitarianism and lack of possessions, people in settled societies developed a new social structure with elites, specialization of roles, and ownership of property. Human groups started for the first time to produce storable surplusses of foood and other products, which led to more complex societies and to increased trad between groups. p. 9
Human evolution did not halt in the distant past but has continued to the present day.
People probably once spoke a single language from which all contemporary languages are derived.
The human genome contains excellent records of the recent past, providing a parallel history to the written record.
Chapter 2: METAMORPHOSIS
Fifty thousand years ago, in the northeastern corner of Africa, a small and beleaguered group of people prepared to leave their homeland. The world then was still in the grip of the Pleistocene ice age. Much of Africa had been depopulated and the ancestral human population had recently dwindled to a mere 5,000
Those departing, a group of perhaps just 150 people, planned to leave Africa all together. Forsaking their familiar habitat was a serious risk since, as hunters and gatherers, their survival depended on intimate knowledge of local plants and animals. Nor is long distance travelever easy for foragers who own no pack animals and must carry every necessity -- weapons, infants, food and water.
The emigrants faced another danger in the world beyond. The lands outside Africa were not unpopulated. About 1.8 million years ago, during a warm interlude before the Pleistocene ice age began, early humans had left Africa in one or more migrations. Once separated from the main human population in the African homeland, these archaic people had followed their own evolutionary paths and in the course of time had become the distinct species known as Homo erectus and Homo neanderthalensis. Erectus settled in East Asia. The Neanderthals occupied Europe and intermittently parts of the Near East. p. 10
. . .
“Why was the little group that left 50,000 years ago able to succeed when all earlier emigrants had failed? What drove them to take such a chance? What ties bound bound these people together and gave them the means to prevail?
To address such questions requires stepping back to the point in evolutionary time when the human line of descent split from the chimpanzee line. This is the moment at which our ancestors started to acquire the first of the adaptations that differentiated them from apes. These changes affected not just physical form but also the set of behaviors that together make up human nature. Of particular importance are the social behaviors, because both apes and and people survive not as individuals but in social groups. In this sense the essence of human evolution is the transformation from ape society into human society.
Given the acute social intelligence of chimpanzees and bonobos, the emergence of human was perhaps not so great a leap. But the human lineage had the fortune to move down evolutionary paths that enlarged the brain and made possible the acquisition of language. The reason the ancestral human population was eventually able to burst out from its homeland seems to have been that 5 million years after having parted company with apes, it had at last perfected this critical component of human sociality. p. 11
Chapter 4: EDEN
It is tempting to suppose that our ancestors were just like us except where there is evidence to the contrary. This is a hazardous assumption. The ancestral human population is separated from people today by some 2,000 generations. In evolutioary time, that is not so long, yet is still time enough for very substantial evolutionary change to have taken place. p. 70-71
Consider that the anatomically modern humans of 100,000 years ago showed no sign of modern human behavior. They had no apparently capacity for innovation and may have lacked the faculty of speech. Very significant evolutionary change seems to have occurred in the 50,000-year span that separates them from behaviorally modern humans of the ancestral population. Yet that is the same span of time that separates the ancestral population from people today, allowing for an equally decisive evolutionary change. And the pace of human evolution may well have accelerated in the last 50,000 years, given the unparalleled changes in environment experienced by the ancestral people as they left their homeland, colonized strange lands and cold climates, and converted from foraging to settled life [emphasis added].
Indeed specific evidence has now emerged suggesting that the human brain has continued to evolve over the last 50,000 years. The evidence, ... rests on the finding that two new versions of genes that determing the size of the human brain emerged only recently, one around 37,000 years ago and a second at 6,000 years ago. Given the brain's continued development, the people of 50,000 years ago, despite archaeologists' tag for them as "behaviorally modern," may have been less cognitively capable than people today [emphasis added]. p. 71
The ancestral population would have lived by hunting and gathering. ... In its homeland in northeast Africa, ... They would have possessed a carefully thought out suite of tools for hunting, food preparation, and carrying things. To judge by the journey of those who were about to leave Africa, they probably knew how to build boats and how to fish.
But their technology would have been considerably less sophisticated than that of the !Kung. The !Kung's lightweight bows and poisoned arrows represent a high degree of mechanical and biological knowledge. There is no clear evidence that the bow was invented until some 20,000 years ago. It never reached Australia, suggesting it was not known to the ancestral human population. p. 71
Without projectile technology, male hunting success in early human societies would have been considerably less spectacular. Large animals would have been hard to kill. . . . But women's foraging, for plant foods and tubers excavated with digging sticks, may have been much the same as in contemporary foraging societies. p. 72
In appearance, the ancestral human population would certainly have had dark skin as protection against the African sun. They had stronger bones and were thicker set than contemporary people. They would have have cut and styled their hair. From the date assigned to the evolution of the human body louse, which lives only in clothing, the ancestral people must have worn clothes that were sewn to fit the contours of the body tightly enough for the lice to feed [emphasis added].
. . .
The ancestral people spoke a fully articulate language, which may well have included the click sounds still used by their Khoisan-speaking descendants.
As hunters and gatherers, the ancestral people probably lived in small egalitarian societies, without property or leaders or differences of rank. These groups engaged in constant warfare, defending their own territory or raiding that of neighbors. When they grew beyond a certain size, of 150 or so people, disputes became more frequent, and with no chiefs or system of adjudication, a group would break up into smaller ones along lines of kinship. p. 72
Yet these quarrelsome little societies would have contained in embryo teh principal institutions of the large modern societies of today. They had some form of religion, a practice that seems as old as language and may have evolved with it. Relition may have served as an extra cohesive force, besides the bonds of kinship, to hold societies together for such purposes as punishing freeloaders and miscreants or uniting in war. pp. 72-73
A sense of fairness and reciprocity governed exchange and social relationships. Much later, the idea of reciprocity would be extended to non-kin, allowing strangers to be treated as honorary relatives and creating the framework for societies that transcended the kin-bonded tribe. Warfare may have been a dominant factor in the ancestral population's existence. A group could attain respite from conflict by finding new territory. Yet it could not have been easy to travel far from the ancestral homeland. Foragers are adapted to surviving in their local environment by their intimate knowledge of its plants and animals. Only one group of people, a little band maybe only a few hundred strong, succeeded in overcoming the daunting odds and leaving the homeland altogether. But by daring so much, they gained the whole world [emphasis added].
Chapter 12: EVOLUTION
"... with his god-like intellect which has penetrated into the movements and constitution of the solar system — with all these exalted powers — Man still bears in his bodily frame the indelible stamp of his lowly origin." Charles Darwin, The Descent of Man p. 264
Darwin's insight was the more remarkable because he had no concept of genes, let alone of DNA, the chemical script in which the genetic instructions are inscribed. Not until 1953 was DNA recognized to be the hereditary material and only since 2003 has the fully decoded script of the human genome been avialable for interpretation. p. 265 Human nature is the set of adaptive behaviors that have evolved in the human genome for living in today's societies. We have developed, and can execute instinctively, the behaviors necessary for warfare, for trade and exchange, for helping others as if they were kin, for detecting outsiders and cheaters, and for immersing our independence in the ["]religion["] of our community. The narrative of the human genome explains our origins, our history, and our nature, but many of its implications are far from welcome to one group or another. "The human mind evolved to believe in gods. It did not evolve to believe in biology," Writes Edward O. Wilson. . . . p. 266 "... the human lineage, seeking a way of life beyond the trees, became so different because it was constantly forced to innovate. p. 266