What Is Chemosynthesis? (with pictures) - wiseGEEK
are created by undisturbed organism remains that become saturated with various chemicals, which gradually replace the organic material with rock by . Few life forms ever become fossils but are instead consumed by other life. Rare dynamics lead to fossil formation, usually by anoxic conditions leading to undisturbed sediments that protect the evidence and fossilize it. Scientists estimate that only about 1%-2% of all species that ever existed have left behind fossils that have been recovered. Geological processes are continually creating new land, both on the continents and under the ocean. Seafloor strata do not provide much insight into life’s ancient past, particularly fossils, because the process in “mere” . The basic process is that, in the Atlantic and Pacific sea floors in particular, oceanic volcanic ridges spew out basalt and the plates flow toward the surrounding continents. When oceanic plates reach continental plates, the heavier (basaltic) oceanic plates are subducted below the lighter (granitic) continental plates. Parts of an oceanic plate were more than 100 mya and left behind plate fragments. On the continents, however, as they have floated on the heavier rocks, tectonic and erosional processes have not obliterated all ancient rocks and fossils. The oldest “indigenous” rocks yet found on Earth are . have been dated to 3.5 bya, and fossils of individual cyanobacteria have been dated to 1.5 bya. There are recent claims of finding . The oldest eukaryote fossils found so far are of . The first amoeba-like vase-shaped fossils date from about 750 mya, and there are recent claims of finding the first animal fossils in Namibia, of sponge-like creatures which are . Fossils from might be the first animal fossils, and some scientists think that animals may have first appeared about one bya. The first animals, or , probably descended from . The is a tail-like appendage that protists primarily used to move and it could also be used to create a current to capture food. Flagella were used to draw food into the first animals, which would have been sponge-like. When the first colonies developed in which unicellular organisms began to specialize and act in concert, animals were born, and it is currently thought that the evolution of animals probably only happened . In interpreting the fossil record, there are four general levels of confidence: inevitable conclusions (such as ichthyosaurs were marine reptiles), likely interpretations (ichthyosaurs appeared to give live birth instead of laying eggs), speculations (were ichthyosaurs warm-blooded?), and guesses (what color was an ichthyosaur?).
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Earth had never before hosted anything like behaviorally modern humans. Nothing came close. They wielded fire and began using it for offensive purposes, to . They had sophisticated stone tools and weapons, they mastered language and could engage in group behaviors that no other land animal remotely accomplished. They probably had sophisticated projectile weapons, and if the , they may have also . One !Kung arrow can bring down a 200-kilogram antelope in less than a day. What kind of animal in the Western Hemisphere and Australia, that had never seen anything like a human before, and would have been the of the invaders, and the large ones all reproduced slowly, could have withstood that onslaught? None that I can think of. Neanderthals were ambush predators of megafauna that were wary of humans, and whatever projectile weapons they may have had, they would have been inferior to those that behaviorally modern humans left Africa with about 60-50 kya. Neanderthals still lived off of those animals, with suffered during hunts. That would have been nothing like what the invaders of the Western Hemisphere and Australia encountered. They could have walked right up to all of those animals with no conditioned fear of humans and stuck their spears into them, maybe not even needing to use projectile weapons, much less poisoned ones. That scenario has been called the , but it would not have seemed a rapid event to the invaders. It would have been a butcher shop’s version of the Garden of Eden. Farther than they could imagine, in every direction, were animals with no fear of humans that could be killed so easily that it may have literally become child’s play. One argument by human-agency skeptics is that continental animals were subject to predation and would have begun fleeing fast. That seems like a weak argument, and here is why.
On numerous fronts, humanity is staring into the abyss, primarily due to our energy practices. The USA's and may be seen by future historians, if there are any, as the , as humanity fights over Earth's last remaining high-EROI energy resources. One of Einstein’s was, “I do not know with what weapons World War III will be fought, but World War IV will be fought with sticks and stones.” Maybe some of us survive that holocaust and the . Maybe we will avoid fighting over hydrocarbons, but the oceans will rise as climate changes more dramatically and billions are displaced. That will trigger global famine and a different kind of World War III, as nations fight over food (and maybe water), not oil. can drive people to drink and worse. Humanity stands on the chasm’s edge today, and hardly any people know or care, as their immediate self-interest marks the limit of their awareness. It has always been this way, when people are just trying to survive and deaden the pain of their existences. The intense denial reactions that Brian encountered when he played the were standard.
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Some nonliterate societies do not engage in warfare. They are a vanishingly small proportion of the world’s native societies, but almost without exception, they are not warlike because they are geographically isolated. The most important variable in predicting a society’s level of internal and external violence is male dominance. Monkeys are (matrilineal), and males leave their society of birth to mate, gorillas and chimps are (patrilineal), where females leave their natal society to mate, and humans have both kinds of pre-state societies, along with some . Patrilocal societies are run by gangs of related men, are by far the most violent, engage in the most warfare, and women are subjected to the most violence. Patrilocal societies can also have harems or many “wives” for the alpha males. Patrilocal societies make up nearly 70% of the world’s native cultures that have been documented. Neanderthals and australopiths . The primary determinant of patrilocal or matrilocal residence in humans is the economic contribution of women. In general, where gathering and horticulture brought in more calories than hunting, women had more influence and the society tended to become matrilocal. Those relationships only hold for societies that are not economically centralized. When surplus redistribution appeared, men began to dominate, and the chiefdom was the first step toward state formation. Organized violence only began increasing as states began to form.