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.
Did the control of fire to , ? Or did merely use it to begin dominating the world? Was cooking the seminal event in the appearance of humans? Those questions may not be definitively answered in my lifetime, and led to the somewhat uncertain title of this chapter. Highly transformative developments coincided with the appearance and dispersal of , which was a radical break from all that came before – biologically, technically, and culturally – and strongly implies great cognitive enhancements. I believe that the control of fire and cooking would leave deep cultural and biological impacts on the human journey, and because barely changed during its nearly two-million year tenure on Earth, both in biology and in Acheulean artifacts, I favor Wrangham’s hypothesis, at least until the Next Big Finding. Just as Einstein said that and that his theories would one day become obsolete, but that their best parts would survive in the new theories, I suspect that significant aspects of Wrangham’s hypothesis will live on in successor hypotheses, and other scientists have been following Wrangham’s lead.
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.
In the early 19th century, a dispute was personified by , a British lawyer and geologist, and , a French paleontologist. Their respective positions came to be known as and . Just as , so did uniformitarianism prevail in scientific circles. Under the comforting uniformitarian worldview, there was no such thing as a global catastrophe. Changes had only been gradual, and only the present geophysical, geochemical, and biological process had ever existed. The British Charles Darwin explicitly made Lyell’s uniformitarianism part of his evolutionary theory and he proposed that extinction was only a gradual process. Cuvier was , which contradicted the still-dominant Biblical teachings, even in the . Although Cuvier did not subscribe to the , his catastrophic extinction hypothesis was informed by his fossil studies. But Lyell and Darwin prevailed. Suggesting that there might have been catastrophic mass extinctions in Earth’s past was an invitation to be branded a pseudoscientific crackpot. That state of affairs largely prevailed in orthodoxy until the 1980s, after the was posited for the dinosaurs’ demise. An effort led by a scientist publishing outside of his field of expertise (a ) removed from its primacy. Only since the 1980s have English-speaking scientists studied mass extinctions without facing ridicule from their peers, which has never been an auspicious career situation. Since then, many and mass extinction events have been studied, but the investigations are still in their early stages, partly due to a dogma that prevailed for more than a century and a half, and Lyell’s uniformitarianism is influential. The ranking of major mass extinctions is even in dispute, , and a was recently .
[tags: beliefs, questions, science, religion]
Speciation has probably been more controversial than extinction. To be fair to Darwin, genetics was not yet a science when was published in 1859. It was not until the by Silesian friar Gregor Mendel that the science of genetics began, but Mendel’s work was until the 20th century. Darwin went to his grave unaware of Mendel’s work. Today, speciation is primarily considered to be a genetic event. But similar to how that dictate their function, and that appear at higher levels of complexity, the DNA code by itself does not explain life, although the popular frames life and evolution as a .
Are science and religions simply both similar social constructions.
The respiration and photosynthesis cycles in complex organisms have been the focus of a great deal of scientific effort, and cyclic diagrams (, ) can provide helpful portrayals of how cycles work. Photosynthesis has several cycles in it, and Nobel Prizes were awarded to the scientists who helped describe the cycles. Chlorophyll molecules , with magnesium in their porphyrin cages, and long tails. Below is a diagram of a chlorophyll molecule. (Source: Wikimedia Commons)
[tags: Science Religion Creation ]
As with other early life processes, the first photosynthetic process was different from today’s, but the important result – capturing sunlight to power biological processes – was the same. The scientific consensus today is that a respiration cycle was modified, and a in a was used for capturing sunlight. Intermediate stages have been hypothesized, including the cytochrome using a pigment to create a shield to absorb ultraviolet light, or that the pigment was part of an infrared sensor (for locating volcanic vents). But whatever the case was, the conversion of a respiration system into a photosynthetic system is considered to have only happened , and all photosynthesizers descended from that original innovation.