Before the Dawn: Recovering the Lost History of Our Ancestors

by Nicholas Wade

  The reason is that settled societies permit individuals to acquire extra property or status, both of which barely exist in hunter-gatherer societies and are in any case frowned on by their egalitarian ethos. Property, in turn, is a way of securing survival for oneself and one’s family. For long periods of human history possession of excess property probably helped people raise more children, even though a direct relationship between wealth and progeny is not so evident in modern societies. Settlement, in other words, would have created a quite novel environment, to which people probably adapted by developing a different set of behaviors, including a range of intellectual skills for which there was no demand in hunter-gatherer societies.

  Property, value, number, weight, measurement, quantification, commodity, money, capital, economy—these concepts, however natural to the modern mind, would rarely have come into play in the life of mobile foragers. Could it be that the modern mind, the one capable of abstract thought, symbolic notation and writing, is indeed a quite recent development? Perhaps the process by which the modern mind emerged “has to be regarded as a more gradual one, operating in several phases and stages, and perhaps independently in different parts of the world,” writes the Cambridge archaeologist Colin Renfrew.153

  That, in his view, might explain why human societies apparently accomplished so little for so long. “If human societies of the early Upper Paleolithic had this new capacity for innovation and creativity which notionally accompanies our species, why do we not hear more about them?” he asks. There is a 45,000-year delay between the time of the ancestral human population and the first great urban civilizations, such as those of Babylon, Egypt, the Harap pan cultures of India and the Shang period of China. If “behaviorally modern” humans evolved 50,000 years ago, why did it take so long for this modernity to be put into practice? Renfrew calls this gap the “sapient paradox.”

  One possibility is that some evolutionary adaptation had first to occur in human social behavior. That would explain why it took so many generations for people to settle down. The adaptation, probably mediated by a suite of genetic changes, would have been new behaviors, perhaps ones that made people readier to live together in larger groups, to coexist without constant fighting and to accept the imposition of chieftains and hierarchy. This first change, of lesser aggressiveness, would have created the novel environment of a settled society, which in turn prompted a sequence of further adaptations, including perhaps the different set of intellectual capacities that is rewarded by the institution of property.

  A striking change that preceded settlement is a worldwide thinning or gracilization of the human skull. This change, discussed further in the next chapter, was probably accompanied by a taming or greater sociability, doubtless a necessary step toward settling down in larger groups.

  If such a change occurred, it evidently evolved independently in different regions of the world, just as have other human adaptations like pygmy stature and lactose tolerance. Direct evidence for such a change may emerge in time from the human genome once the genes that influence human social organization are identified.

  Once people were settled, many new opportunities for human innovation were opened up in technology, trade, warfare and political organization. A salient new technology was that of agriculture, which was invented before the end of the Pleistocene ice age and took off as soon as the climate started to warm up in the Neolithic. The reason for agriculture’s rapid spread, archaeologists believe, was that societies of the Near East had preadapted to it, primarily by sedentism but also with efforts to intensify production by seeding wild grasses.154 Many previous theories about the invention of agriculture have invoked external forces that allegedly pushed a passive human society into taking up cultivation. None is well supported. One thesis holds that population pressure drove people to agriculture. But the archaeological evidence is that human populations grew after the advent of agriculture, not before it. Another proposal is that the warming of the climate after the end of the Pleistocene ice age was the driving force. But climate improvement was much the same everywhere, yet agriculture emerges at very different times in different regions of the world.

  “It is important to realize,” write Akkermans and Schwartz, “that farming was neither the production of food according to an economic rationale nor an inevitability imposed on early Neolithic communities by large-scale events beyond their control. Instead, the adoption of agriculture was part of the profound transformation of the entire forager society and an adjustment to a wholly different set of societal values and meanings.”155 Sustenance is not the only reason for agriculture. One advantage enjoyed by settled societies, and denied to foragers, is the ability to generate and store surpluses. Surpluses form the basis for trade. They can be exchanged for things considerably more vital than extra food, like weapons, or alliances, or prestige.

  Settlement and Domestication

  By the end of the Pleistocene ice age 10,000 years ago, the second human revolution was well in place, that of reengineering the mobile, kin-based, foraging band into a settled society, bindable by ties of altruism and religion into larger groups. Societies of the Near East were the first to take this crucial step, one that enabled human inventiveness to thrive in a new setting. Specialization of roles may have occurred for the first time, which would have led to increased productivity. Productivity creates surpluses, and surpluses of one commodity can be traded for another with a neighboring group. Settlement, specialization, property, surplus, trade—these are the sinews of economic activity, setting humans at long last on a separate path from living off nature’s bounty like all other species.

  Late Pleistocene peoples like the Natufians developed the technology of threshing and milling wild grains they had collected. They also began to cultivate wild grains, perhaps when the cold snap of the Younger Dryas shrank the natural expanses on which settled communities had become dependent.

  It would only have been a short step from cultivating natural wild grasses to selecting specific types. The step may have taken place unwittingly. Einkorn wheat, emmer wheat and barley, three wild cereals that grow in the region of the Fertile Crescent, all have the property of shedding each kernel from an ear as it ripens. The domesticated varieties, on the other hand, keep all the kernels attached so all can be harvested together. If people harvested the wild varieties by knocking the sheddable ears off into baskets, any rare nonshedding mutant would be left to the end of the harvest. These would have served as the seed stock for the next generation, and the unconscious selection for nonshedding varieties would quickly have driven up the frequency of the nonshedding gene.

  Unconscious selection may also have eliminated another undesirable feature of wild cereal grasses—their ability to inhibit their germination so as to avoid the trap of developing in a drought year.156 Seeds that decided not to germinate would have been automatically eliminated in favor of mutants that did so in all weathers.

  The transformation of cultivated wild cereals into their domestic forms could have happened very quickly, in as little as 20 to 30 years. That and other genetic considerations have been taken to mean that domestication of wheat was easy and might have happened several times independently.157 But a genetic family tree drawn up for domesticated and wild varieties of einkorn wheat shows that the domesticated varieties all cluster on one branch, indicating a single domestication. The same is true for barley.158

  Archaeologists have not so far found any single site where they can trace the progression from the wild form of a cereal to its domesticated versions. But genetics has provided an unexpected helping hand in the case of einkorn wheat. Francesco Salamini, of the Max Planck Institute for Plant Breeding Research in Cologne, Germany, with colleagues in Norway and Italy, analyzed nearly 1,400 strains of wild einkorn wheat from the Near East. Those with a genetic structure closest to the domesticated strains came from the Karacadağ mountains of southeastern Turkey. The region is close to sites in northern Syria, like Abu Hureyra, where domestic
ated einkorn is known to have been grown some 8,500 years ago. The researchers conclude that “the Karacadağ mountains are very probably the site of einkorn domestication,” a claim disputed by some but endorsed by Daniel Zohary, a leading expert on plant domestication.159

  Einkorn was apparently the first wild cereal to have been domesticated. It was cultivated some 12,500 years ago and the first possible domesticated forms occurred 10,500 years ago; domesticated einkorn becomes abundant in the western half of the Fertile Crescent (from southeastern Turkey down the east Mediterranean coast) from 9,500 years ago. Domesticated emmer wheat, which is easier to harvest, is found at Abu Hureyra from 10,400 years ago. (Einkorn wheat mostly ceased to be planted in the Bronze Age; emmer is still grown in Ethiopia. Modern wheats stem from an accidental cross between a domesticated variety of emmer wheat and a wild grass known as Aegilops squarrosa or tauschii. The hybridization is thought to have occurred in the region of northern Iran some 7,000 years ago.) Rye and barley were two other wild cereals domesticated before 10,000 years ago in the Fertile Crescent.160

  After the dog, the first animals to have been domesticated were sheep and goats, probably between 10,000 and 9,500 years ago. Cattle were domesticated from the aurochs at about the same time, and the pig from wild boar. The aurochs ranged widely across Europe as well as the Near East, but a comparison of British aurochsen (based on mitochondrial DNA extracted from fossil bones) with modern cattle shows that Europe’s cattle too were domesticated in the Near East.161 It may be that these animal species, like the wild cereals, were domesticated unconsciously, in a process that started with wild herds being penned and the tamer animals picked as parents of the next generation. This assumes that people of 10,000 years ago were not aiming at domestication because they had no idea it could be achieved. On the other hand, they had the dog as an example, and a growing number of instances of their own success.

  The horse appears to have been domesticated much later and outside the Near East, probably on the Eurasian steppes. Wild and domesticated horse bones are hard to tell apart, but horse remains with possible bit wear on the teeth occur in archaeological sites of the Ukraine and Kazakhstan, starting from 6,000 years ago. Unlike other animal species so far studied, which appear to have been domesticated only once or twice, horses seem to have been domesticated on many separate occasions, according to a study based on mitochondrial DNA.162 Possibly it was the technology for capturing, taming and rearing wild horses that spread from one society to another, rather than a strain of domesticated animals. If so, this would suggest that horses were of such high value, perhaps for military purposes, that people rushed to domesticate their own rather than waiting to acquire a breeding pair.360

  The people of the Near East, having developed suites of domesticated plant and animal species, expanded their farming activities north and west into Europe. Archaeologists have generally assumed that these farmers could support more people and that their populations must have crowded out the original inhabitants of Europe who had entered as foragers during Upper Paleolithic times. But the founder analysis undertaken by Richards, as mentioned in the previous chapter, shows that only a small percentage of today’s Europeans are descended from those who entered from the Near East in Neolithic times.

  Presumably a few farmers from the Near East entered Europe, and perhaps the original inhabitants started to imitate their success, by settling down and adopting the new technology. Or the new farming groups, if composed largely of men in search of new land, may simply have captured women from the indigenous groups. The farmers’ Neolithic genes would have become more diluted, generation by generation, as they and their new culture pushed farther into Europe.361

  Whatever the mechanism of spread, only 4 of the 10 principal Y chromosome lineages found in today’s Europeans arrived during Neolithic times. These 4 lineages, according to Semino and Underhill, account for 22% of European Y chromosomes, a reasonable match with mitochondrial DNA data suggesting that 13% of Europeans have Neolithic heritage.163

  It is only a coincidence of timing that associates these Y chromosomes with the Neolithic, and, given the approximate nature of dates derived from genetics, it would be reassuring to have some more direct link. One has emerged from the painted pottery and figurines associated with Neolithic sites. The pottery, known as LBK from the German words for “linear band ceramics,” was made in the Near East, the home of the Neolithic revolution, as well as in Greece, the Balkans and southern Italy. Two Stanford University researchers, Roy King and Peter Underhill, matched the geographical distribution of LBK pottery and figurines with that of the four Y chromosome lineages that entered Europe at the beginning of the Neolithic age. They found that one lineage in particular, marked by the mutation known as M172, was found in almost exactly the same locations as the LBK culture.164 The present day male population with the highest known frequency of M172 happens to live in Konya, a city near the southern coast of Turkey and some 60 miles from the well known Neolithic site of Çatal Höyük. No less than 40% of men in Konya carry M172 on their Y chromosomes.

  The finding supports the idea that Neolithic farmers from the region of Çatal Höyük pushed into Europe, gradually mixing with the local population. Their farming techniques and pottery making became universal, even though their genes did not. The intriguing question of whether they introduced the Indo-European languages into Europe is addressed in chapter 10.

  The Interaction of Genes and Culture: Lactose Tolerance

  While people were shaping the genetics of domesticated plants and animals by altering various features of their environment, a curious thing was happening to people themselves. Their genetics too were changing as they adapted to the new environment of settled societies.

  The warriors and mighty hunters who left the most children in hunter-gatherer societies may have lost their advantage in settled societies. The ability to support many children would have passed to those who excelled at the new occupations of farmer, priest, clerk or administrator. After many generations, and maybe not so many if the selection pressure was intense, people in settled communities may have developed a distinct suite of behaviors that set them apart from their hunter-gatherer forebears.

  This conjecture cannot yet be addressed, because the genes that underlie human behavior are still for the most part unknown. But the ease with which the human genome responds to cultural changes in society has come to light from a physiological adaptation, the unusual ability to continue to digest lactose in adulthood, otherwise known as lactose tolerance.362

  Though cattle were first domesticated in the Near East, Europe became a center of cattle breeding during one of its first farming cultures, known from its pottery as the Funnel Beaker culture. The culture, which lasted from 6,000 to 5,000 years ago, was located in north-central Europe in the region that now includes the Netherlands, northern Germany, Denmark and southern Norway. It has left a lasting mark on the genetics of both the cattle and human populations of the region.

  A team of European researchers led by Albano Beja-Pereira recently studied genes that encode the 6 most important milk proteins in 70 breeds of European cattle. From samples taken from 20,000 cattle, they drew up a map showing the degree of genetic diversity in the cattle genes. The greatest diversity—usually the sign of a species’ original homeland—coincided closely with the territory archaeologists have defined for the Funnel Beaker culture.

  The researchers then performed the same mapping exercise for the human genetic trait known as lactose tolerance, the ability to digest lactose in adulthood. They found that the highest percentage of people with lactose tolerance occurred among populations in a region that substantially overlapped with the ancient territory of the Funnel Beaker culture. The frequency of lactose tolerance dropped off progressively with distance among populations outside the core area.165

  This finding is remarkable because it shows a human population evolving, in recent times, in response to change created by human culture. Lactose is a speci
al sugar that accounts for most of the caloric content of mother’s milk. The gene for lactase, the enzyme that digests lactose, is switched on just before birth and, in most people, switched off after weaning. Because lactose does not occur naturally in most people’s diet, it would be a waste of the body’s resources to continue making the lactase enzyme. But in people of mostly northern European extraction, and to some extent in African and Bedouin tribes that drink raw milk, the lactase gene remains switched on to early adulthood or throughout life. Among these milk drinkers, the ability to digest the lactose in cow’s, sheep’s or goat’s milk evidently conferred so great a benefit that the genetic mutation conferring the ability became widespread.

  Geneticists are still trying to define the exact genetic change that causes the lactase gene to stay active after weaning. The DNA sequence of the lactase gene itself is identical in both lactose tolerant and intolerant people. The difference must lie in some nearby region of DNA that controls the activation of the lactase gene, such as the two mutations recently discovered by Leena Peltonen of the University of Helsinki.166

  What is certain is that lactose tolerant Europeans have inherited unchanged from a common ancestor a huge block of DNA that includes the lactase gene, its neighboring gene and much else. The size of the block is a sign of recent evolutionary change. Big blocks of unchanged DNA are very rare because at each generation pairs of chromosomes swap sections of DNA so as to create individuals with novel combinations of genes. As is easy to envisage, the blocks of original DNA that a chromosome may start off with will get smaller and smaller at each generation as the swapping process whittles them down. So a large block of DNA shared by lots of people is a sign of recent selection. Large blocks are created when some must-have mutation occurs that is greatly favored by natural selection. Nature cannot pick out a specific mutation or gene; it can only favor individuals who have inherited the large block of DNA within which the advantageous gene occurs.