In 2013, average Americans used about 80 times the energy that was provided by their diets, which has been called having 80 energy slaves, but that understates the reality. A barrel of oil provides about one year of the calories needed to fuel a human body, but if that oil were used to power machines, it would perform more than ten man-years of work, often doing work that humans could not perform in any case, such as propelling an automobile. Each American really has several hundred energy slaves working for him/her, which is why the average American lives a richer lifestyle than Earth’s richest human of two centuries ago. In 2013, the energy in the oil wrested from Earth’s crust contained enough energy to power several hundred energy slaves. Add in the other energy resources, and industrialized humanity rode on the backs of about one energy slaves. In today's industrialized nations, humans perform a tiny fraction of one percent of the actual work done; energy-powered machines perform more than 99.9% of it. In contrast, the reproduction of intelligence is in its infancy. In 2012, humanity's 500 most powerful supercomputers achieved the combined computing power of three human brains. The day that each human has even one "mind slave" is a distant future event.
It can be helpful at this juncture to grasp the cumulative impact of , inventing , inventing , inventing that made possible, and inventing . Pound-for-pound, the complex organisms that began to dominate Earth’s ecosphere during the Cambrian Period consumed energy about 100,000 times as fast as the Sun produced it. Life on Earth is an incredibly energy-intensive phenomenon, powered by sunlight. In the end, only so much sunlight reaches Earth, and it has always been life’s primary limiting variable. Photosynthesis became more efficient, aerobic respiration was an order-of-magnitude leap in energy efficiency, the oxygenation of the atmosphere and oceans allowed animals to colonize land and ocean sediments and even fly, and life’s colonization of land allowed for a . Life could exploit new niches and even help create them, but the key innovations and pioneering were achieved long ago. If humanity attains the , new niches will arise, even of the , but all other creatures living on Earth have constraints, primarily energy constraints, which produce very real limits. Life on Earth has largely been a for several hundred million years, but the Cambrian Explosion was one of those halcyonic times when animal life had its greatest expansion, not built on the bones of a mass extinction so much as blazing new trails.
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The (c. 15 kya to 11.8 kya) succeeded the Kebaran culture. The Natufian village at in today’s Syria was established about 13.5 kya and was situated on a gazelle migration route. The residents of that village of a few hundred people also . Those villagers became Earth’s first known farmers, and they had dogs. The during the Younger Dryas and resettled after it ended. The effect of a harsher climate may have , which began there about 11 kya. By seven kya, the settlement had grown to several thousand people, and was then abandoned due to aridity. No evidence of warfare is associated with the settlement. A compelling recent hypothesis is that agriculture could not have developed in warfare’s presence, as farmers would have been too vulnerable to raids by hungry hunters. In the four places on Earth where civilization seems to have independently developed: the Fertile Crescent, China, Mesoamerica, and the Andes, no evidence of violent conflict exists before those civilizations, fed by the first crops, began growing into states. Those states are called “pristine” states, as no other states influenced their development. Also, it is considered likely that a primary impetus for beginning agriculture in those regions was the decimation of animals to hunt. Not only was the easy meat rendered largely extinct, but those animals would have also been competitors for crops. The peaceful agricultural villages that , in which women's status was closer to men's than at any time before the Industrial Revolution, actually existed, if only for a relatively brief time, in only a few places.