Investigating the Cryogenian Ice Age led to finding evidence of runaway effects causing dramatic environmental changes, and the Cryogenian Ice Age’s dynamics will be investigated and debated for many years. The position of Antarctica at the South Pole and the landlocked Arctic Ocean have been key variables in initiating the current ice age, and another continental configuration that could contribute to initiating an ice age is , which and . A hypothesis is that can accompany supercontinents, so warm water is not pushed to the poles as vigorously. A supercontinent near the equator would not normally have ice sheets, which means that would be enhanced and remove more carbon dioxide than usual. Those conditions could initiate an ice age, beginning at the poles. It would start out as sea ice, floating atop the oceans.
The of an ice age is only a few hundred years old, and was , who got his first ideas from and others. There had also been . By the 1860s, most geologists accepted the idea that there had been a cold period in Earth’s recent past, attended by advancing and retreating ice sheets, but nobody really knew why. Hypotheses began to proliferate, and in the 1870s, proposed the idea that variations in Earth’s orientation to the Sun caused the continental ice sheets. Because of problems in matching his hypothesis with dates adduced for ice age events, it fell out of favor and was considered dead by 1900. Croll’s work regained its relevance with the publication of a paper by (usually spelled Milankovitch in the West) in 1913, and by 1924, Milankovitch was widely known for explaining the timing of advancing and retreating ice sheets during the current ice age.
The other critical innovation was the modern steam engine, which was intimately related to coal. Burgeoning coal mines quickly exhausted deposits above the water table and began digging deeply into the earth, and water in the mines became a great problem. Not only were floods killing miners, but standing water made mines inoperable. Romans pumped water from their mines (). So did British mining operations, and around 1710, combined the ideas of a and an to make the , to pump water from coal mines. In a parallel case of using coal for smelting, the coal-fired Newcomen engine was . It was the first of its kind, primitive compared to later engines, and its spread was gradual. . He eventually invented an improved version with a that was . The steam engine that powered the Industrial Revolution was thus born, although, as with coal, its spread was gradual, and wind and water power were competitive with coal for nearly a century. The hydrocarbon-fueled steam engine was the key to the Industrial Revolution, in which the energy of ancient sunlight was exploited to generate previously unimaginable power. A steam locomotive of 1850 roaring through the English countryside would have been inconceivable to an English peasant of 1500. From a to to to less than five hundred years, the duration of each Epochal Event continued to shrink as levels of energy use increased dramatically and with each event.
In 1750, only 5% of England’s pig iron was produced with coke, but by 1800, with and the continuing rising price of charcoal, British pig iron production was 150,000-200,000 metric tons annually, and almost all was coke-smelted. It was ten times greater than annual production in the 18th century’s first half, and the steep ascent began in the 1770s. In the first decade of the 19th century, it doubled again. During the 18th century, British coal production increased five-fold, to more than 15 million metric tons, and it doubled again by 1830. It took ten times its weight in fuel to produce ten tons of iron, and twenty times for copper. One reason for iron’s relative “cheapness,” energy-wise, is that life processes into oxides. In 1900, the British produced five million tons of pig iron annually, the USA produced twice as much, and Germany produced more than six million tons. In 2011, the UK produced only seven million tons of pig iron, China produced nearly a hundred times as much, and , which was several thousand times what England, the early leader in industrialization, produced two centuries earlier. In 2008, global coal production was estimated at 5.8 billion metric tons, which was nearly 400 times what the UK mined in 1800.
Islamic culture enjoyed humanity’s highest standard of living in about 1200, and although Europe was rising in that period, it was also seen as backward compared to the refined cultures of the Eastern Roman Empire (which never lost the ancient Greek teachings) and Islamic lands. But late Medieval Warm Period droughts may have unleashed a scourge that would be unsurpassed in ferocious destruction until the Nazis in the 20th century: the Mongol invasions initiated by . Islam never fully recovered from the Mongol invasions. , and Baghdad was Islam’s leading city before its and wholesale slaughter of its residents. Places such as China, Russia, and Hungary lost up to half of their populations. A recent study suggested that the tens of millions of deaths at the Mongols' hands may have initiated reforestation that absorbed carbon dioxide from the atmosphere to such an extent that it helped end the Medieval Warm Period. The impact was only about 1 PPM, and the coming Little Ice Age has , including the Western Hemisphere’s depopulation and reforestation due to the Spanish invasions of the 1500s.
But in medieval Europe, the , beginning with Germanic lords as Rome was falling. Not only did the watermill spread throughout Europe, but new mills such as the and appeared. Today’s France is where most medieval mill innovations appeared, but watermills became universal on the streams and rivers of Europe. In 800, only a few watermills existed in Western Europe, but by 1000 there were hundreds. The of 1086 recorded nearly six thousand watermills in England alone, and the true number was some thousands more. The had 10 thousand watermills at that time, and their number doubled in the next two centuries, as did England’s. Each mill produced at least two-to-three horsepower, which was the equivalent labor of about 50 men. In 11th-century France, its mills produced the labor of a quarter of its population. Medieval European watermills produced the work of millions of people and reduced the need for slaves. It was a prelude to the Industrial Revolution. When Columbus sailed in 1492, watermills performed the work of at least 10 million people in Europe, which had a population of about 75 million. When watermill sites became filled, Europeans began using windmills, which first appeared in France in 1080, although the first . The social organization of medieval Europe was ; peasants labored for landowners in return for a portion of the harvest. The watermill became the center of a struggle between feudal and Church authorities and the peasantry; the windmill was established partly to circumvent lordly claims on waters that passed over their lands, as nobody yet owned the air.
Because the Western Hemisphere’s inhabitants were virtually all in their Stone Age, they as greatly as Old World civilizations did, and many societies were environmentally sustainable and provided seeming answers to questions that scientists have asked about Old World civilizations’ development. The natives of coastal California were familiar with agriculture, as it was practiced by nearby inland tribes, but they never adopted it. California was so bountiful, and its climate was so human-friendly, that its natives retained their hunter-gatherer lifestyle. Similarly, northward on the Pacific Northwest's coast, natives created an economy in which half of its calories derived from salmon runs, and those peoples were relatively sedentary without agriculture. Natives turned the Great Plains into a big pasture for bison, and the biome was partly maintained by annual burning of the grasslands. In Mesoamerica, farming has been sustainable for thousands of years. In the Amazon, the natives transformed the rainforest, and a higher proportion of plants and trees provided human-digestible foods than in any other “wild” place on Earth, those natives also terraformed thin tropical soils with ceramics (maybe unintentional) and charcoals (intentional) and made super-soils called and . In summary, native practices in the Western Hemisphere were often sustainable if not quite abundant. But when civilizations arose, they had problems that were like their Old World counterparts'. Their problems were also environmental and not just the injustices of hierarchal societies, often steeply hierarchical.
Mesoamerica’s Domestication Revolution was one of the two certainly pristine ones known, and the one around today’s Peru may have been another. The other two of the human journey arose there, and they followed the same general patterns as Sumer and China in that they began peacefully with no classes and, as they grew into states, men came to dominate, elites appeared with monumental architecture devoted to them, potentates had harems and divine sanction, and there were other features that seemingly evidenced universal human traits and/or reactions to similar conditions. The development of religion in what became Mesoamerica’s pristine civilization, the , has been documented by archeologists who traced a seven-thousand-year progression from hunter-gatherers to egalitarian early agriculturists to an elite-dominated society to a pristine state. It was similar to how Mesopotamian civilization developed, including the (today’s rock stars have been likened to the new shamans, as their concerts revive pre-civilized gatherings and rituals). Controversial aspects of Mesoamerican societies have included human sacrifice and cannibalism. They definitely happened, and human sacrifice was practiced on a pretty grand scale at times. The question of Western Hemispheric cannibalism has touched on the lack of domestic animals, so it may have had nutritional aspects, or what is called culinary cannibalism. But most seeming cannibalism is of the cultural cannibalism variety, in which eating flesh has symbolic meaning, whether it is eating somebody to keep their spirit in the family/tribe or to gain spiritual dominance over a fallen foe. Cannibalism was a common charge made against peoples that Europe conquered, but was usually a sensational allegation to remove their humanity and justify their bloody treatment by Europe. Columbus made his from whole cloth.
About 1000 BCE, one of the largest migrations in the human journey, the , began, and it expanded because of the Bantus' use of iron and agriculture, and they displaced or absorbed hunter-gatherers as they expanded across sub-Saharan Africa. In a dynamic too common in human history, ; studies provide evidence of this.
I earlier compared people from different epochs. That stone tool Tesla what his/her invention would lead to a half-million years later, and members of the founding group could not have comprehended . Imagine a hunter-gatherer of 10 kya being dropped into Rome in 100 CE or London in 1500 CE. History has some relevant examples. When , about the last of his people, came out of hiding in his dying world and strode into civilization, it caused a sensation. He soon died of tuberculosis, but his encounters with civilization were recorded. He attended an opera, and the popular account portrayed his rapport with the diva, but Ishi actually stared in amazement at the , as he had never before seen so many people in one place. When he saw an airplane in flight, he laughed in amazement. Imagine a hunter-gatherer of 10 kya being dropped into imperial Rome. That hunter-gatherer had probably seen dogs, but horses, cows, sheep, and the like would have been astounding, and watching a horse or ox pull a cart would have been stunning. Crops would have been an amazing sight. Imagine that hunter-gatherer at the . The building and crowd alone would have boggled his mind, even if the festivities might have been horrifically familiar. Metals and glass would have seemed magical. Writing had not yet been invented in that hunter-gatherer’s world, so even the concept would have been difficult. Imagine him trying to learn math. There were no more singing and dancing religious rituals, and no wide-open spaces to hunt a meal. Imagine that hunter-gatherer visiting a Roman bath. Hot water alone would have been surreal, while the cavorting might have been delightful. What would his reaction have been to Rome’s markets? Rome was also loud and could be hellish, so the hunter-gatherer might have longed to flee to the countryside before long, but the countryside would have little resembled the one he knew. He obviously would not have understood anything that anybody said, but they were also all members of , so he would have seen many behaviors and traits that he eventually understood. But how long would his shock have lasted? Could he have really ever adapted to Roman society (if he did not quickly end up on the arena’s stage as a novelty)? Another surprise for that hunter-gatherer would be seeing people interact who did not know each other. People were interacting with members and not trying to kill them on sight, which became standard behavior in most hunter-gatherer societies that battled over territory (their food supply). Civilized life was all made possible by the local and stable energy source that agriculture provided, which led to an epoch that changed very little until the next energy source was tapped: the hydrocarbon energy that powered the Industrial Revolution. The next chapter will survey the developments that led to that momentous event. It is the only Epochal Event with historical documentation that showed how it developed, which is easier to reconstruct than examining stones and bones.