Organisms begin to capture chemical energy.
Taking a sea route was a new accomplishment by those behaviorally modern humans, and they probably reached Australia about 48-46 kya, because the Australian megafauna began going extinct about then, and that event begins a long and bloody tale that continues to this day. Earlier extinctions of the megafauna on , or and , can be considered more equivocal, but there is virtually no doubt among today’s scientists that the began in earnest with the human invasion of Australia.
Organisms begin to directly capture photonic solar energy.
Around when Harland first proposed a global ice age, a climate model developed by Russian climatologist concluded that if a Snowball Earth really happened, the runaway positive feedbacks would ensure that the planet would never thaw and become a permanent block of ice. For the next generation, that climate model made a Snowball Earth scenario seem impossible. In 1992, a professor, , that coined the term Snowball Earth. Kirschvink sketched a scenario in which the supercontinent near the equator reflected sunlight, as compared to tropical oceans that absorb it. Once the global temperature decline due to reflected sunlight began to grow polar ice, the ice would reflect even more sunlight and Earth’s surface would become even cooler. This could produce a runaway effect in which the ice sheets grew into the tropics and buried the supercontinent in ice. Kirschvink also proposed that the situation could become unstable. As the sea ice crept toward the equator, it would kill off all photosynthetic life and a buried supercontinent would no longer engage in . Those were two key ways that carbon was removed from the atmosphere in the day's , especially before the rise of land plants. Volcanism would have been the main way that carbon dioxide was introduced to the atmosphere (animal respiration also releases carbon dioxide, but this was before the eon of animals), and with two key dynamics for removing it suppressed by the ice, carbon dioxide would have increased in the atmosphere. The resultant greenhouse effect would have eventually melted the ice and runaway effects would have quickly turned Earth from an icehouse into a greenhouse. Kirschvink proposed the idea that Earth could vacillate between states.
The earliest economic school of thought was French, and its practitioners were called . They formed the first and so-far only economic school that rooted economic activity and wealth in energy terms. Physiocrats worked before the science of energy was invented, but they understood that land was the basis of wealth, or more specifically, the crops, timber, metals, and other resources that could be wrested from them via labor (AKA ""). Physiocrats were opportunists who developed economic theories that they planned to profit from, in order to climb into the aristocracy. The first English economist of what later became the was arguably who, like his successors, derived theories that he planned to benefit from. They either tried to join the rising rich classes themselves or performed ideological services on their behalf to curry favor. There was nothing of the disinterested scientist in their work, but they became ideological warriors of the rising capitalist class. It became Karl Marx’s task to name that rising class; he called them the . Preceding the nominal classical economists was , who is called a mercantilist philosopher today, but he was really one of the most honest classical economists in describing the early forces of capitalism, of forcing peasants off the land and enslaving them to market forces.
First large-scale energy users.
About 43 kya, lowering sea levels due to increasing global glaciation formed a land bridge to . People migrated there, too, to become isolated when the seas rose again. The peoples of were the world’s most isolated, not “discovered” until the 1930s. When , the highlanders did not know that a world existed outside of their highland home; they thought that they were Creation’s only people. Unlike other relict populations of the original African migrants, New Guinea Highlanders practiced agriculture and lived in villages, but they were as violent as the others.
First complex ecosystems appear.
When Europeans invaded Australia in the late 1700s, the aborigines they encountered were in a state of almost constant warfare. What seems to be the case is that the founder group of Australia lived in the easy meat days and they grew and spread across the continent in a few thousand years. Once the golden age based on easy meat ended, they reverted back to their territorial natures and formed 600 separate societies, with between 500 and 1,000 people in each one. They all had unremitting hatred for their neighbors, with whom they were in constant warfare. The aboriginal genetic diversity supports the idea that those societies did not interbreed with each other, but stayed insular. They were all patrilocal and violent.
Concentrated application of muscle energy.
The Andamans are members of a racial group called , which appear to be remnant populations of the original migration from Africa. They all survived in marginal environments where they subsisted as hunter-gatherers, while later agricultural immigrants dominated arable lands. About 50 kya, a few thousand years before the migration to Australia happened, the sea level was lower and the islands of , , and formed a contiguous peninsula today called . , Australia, and were also connected and formed a continent today called . Deep water lay between those two “lost continents,” and biologists drew lines between them that noted the distribution of animals and plants that did not cross open water. is farthest north, followed by , and is farthest south. Those lines mark the limits of migrations from Sundaland toward Sahul, which followed sea level changes. About 48-46 kya, behaviorally modern humans crossed the water in boats to Sahul, and the peoples of New Guinea, Australia, and Tasmania largely lived in isolation until Europeans arrived. Those peoples have remnants in their DNA, which probably means that they interbred with them while driving them to extinction on Sundaland and Southeast Asia, before some migrated to Sahul. Aboriginal Australian isolation was almost certainly maintained in the way that Andaman Islanders did it: by killing strange peoples who came ashore. However, in 2012, a paper was published regarding evidence of contact about four kya with people probably from India, when the , , and some Indian DNA admixture were introduced into Australia, which seems related to a colonization of northern Australia by an immigrant population. More of those kinds of migrations of human DNA, technology, and domesticated species have yet to be discovered, and some may even be significant.