c. 4.6 billion years ago (“bya”)
Several different fusion processes have been identified, and stars from about half the size of the Sun to about nine times larger can undergo a process known as late in their lives, and that process has created about half of the elements heavier than iron; is the heaviest element created by the process. Those heavier elements are eventually blown from the star by its stellar wind as it becomes a white dwarf. Stars with more than nine times the mass of the Sun undergo a different process at the end of their lives. When the hydrogen and helium fuel is used up and the fusion processes in those stars’ cores are reduced low enough, gravity will cause those stars to collapse in on themselves. That collapse creates the pressures needed to fuse those other atoms heavier than iron, including the heaviest elements. Uranium is the heaviest naturally produced element. In an instant, . Depending on a composition, it can collapse into a black hole or neutron star or explode into a supernova.
Organisms begin to capture chemical energy.
Specialists are often those on the ground, getting their hands dirty and doing the detailed work that forms the bedrock of scientific practice. Without their efforts, science as we know it would not exist. However, mainstream science has long suffered from the tunnel vision that overspecialization encourages, and thought that the epidemic overspecialization and in his time and unable to see the forest for the trees. That has been slowly changing in my lifetime, so that collaborative efforts are drawing from multiple disciplines and achieving synthetic views that were not feasible in earlier times, and patterns are newly recognized that were invisible in a scientific world filled with isolated specialists. Many were made by non-professionals, specialists working outside of their field of professional expertise, and generalists traversing disciplinary boundaries. Scientific training today attempts to prevent that overspecialized tunnel vision, and today’s practicing scientists ideally get deep into the details and then pull back and try to see context, connections, and patterns. A comprehensivist tries to understand the details well enough to refrain from making unwarranted generalizations while also striving for that big-picture awareness. There are also to approach analyses; each can provide critical insight, and scientists and other analysts often try to use both.
Upriver from Sumer, the , which was the world's first empire. Akkadians began defeating Sumer around 2300 BCE. Akkad’s first king was , who bloodily came to power, captured Uruk, and dismantled its walls while conquering Sumer. That began a pattern of rising and falling empires in the Fertile Crescent that characterized the region for thousands of years. The Akkadian Empire , and there was a resurgence of Ur under its around 2100 BCE; the were then written. The , written when ruled in their turn a few centuries later, reflected earlier Sumerian laws, and they notably documented the barbarity of their times. Murder and robbery were capital crimes, but capital punishment was also meted out for such as , deflowering a wife before the husband could (when the deflowerer is killed), or a wife is unfaithful (when the wife is killed). A boy striking his father would lose his fingers or hand. “” came from the Code of Hammurabi.
Allows for direct energy capture of complex life, and led to plants.
In summary, becoming bipedal had great portent for evolving protohumans, and the suspicion is strong among scientists that it led to feedback loops in which tool use became advanced, which allowed for a richer diet, which helped lead to larger and more complex brains, which led to more advanced thinking and behaviors, which led to more advanced tools, which led to more acquired energy, better protection, and larger brains, and so it went. But the control of fire was a watershed event. Although better tools improved the viability of early humans, on Earth could challenge fire-wielding humans. With the control of fire, humans never had to worry again about being preyed on, nor as a threat to species viability, except by other humans. Naturally, fire was eventually used for offense instead of defense.
, to eventually achieve modern levels, begins
The energy from controlled fire allowed humans to , , and socially organize in new ways. Humans commandeered energy that otherwise and used it for immediate human benefit. It was also the first great human robbery. All heterotrophs “” energy from other life forms to live. The primary exception is the symbiosis that . But no animal had ever robbed energy from ecosystems on that scale before. By making fires, humans were liberating many times the energy that their biological processes used - energy that could have fed forest ecosystems. While humans were only using deadwood, it was the least destructive to forest ecosystems. But when humans began burning forests to flush out animals to kill and make biomes suitable for animals to hunt, they were destroying and altering ecosystems on a vast scale. A cord of wood provides about four years of the calories that fuel a human adult’s body, and one hectare can provide a sustainable annual harvest of about ten years of human calories. A family of four using a hectare for firewood on a sustainable basis would be using more than twice their caloric intake for burning wood. Very little of that released energy would benefit humans if they burned it over a campfire, as humans did for the entire epoch of the hunter-gatherer; that liberated energy largely went straight into the sky. The direct benefit to humans would be the energy that went into cooking food, what warmed human flesh, what was used to make tools, and the benefits of scaring off predators and providing light at night. More indirect benefits would have been ecosystem changes to provide human-digestible calories, such as American Indians burning the woodlands and plains to make environments conducive to animals that they could easily hunt. In , the earliest epochs are the most uncertain, but saying that hunter-gatherer humans used 2.5 times their dietary calories in their economy is probably, perhaps greatly, understating the case. That 5% efficiency number is also a rough estimate, and both numbers could be refined by a scientifically performed effort. Maybe somebody has already done it. The numbers in that table for subsequent epochs are more accurate, and the most accurate of all are those for , and I live in one. The increases in efficiency became more modest with each epoch as the limits of were approached.