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So far in this essay, mammals have received scant attention, but the mammals’ development before the Cenozoic is important for understanding their rise to dominance. The , called , first , about 260 mya, and they had key mammalian characteristics. Their jaws and teeth were markedly different from those of other reptiles; their teeth were specialized for more thorough chewing, which extracts more energy from food, and that was likely a key aspect of success more than 100 million years later. Cynodonts also developed a secondary palate so that they could chew and breathe at the same time, which was more energy efficient. Cynodonts eventually ceased the reptilian practice of continually growing and shedding teeth, and their specialized and precisely fitted teeth rarely changed. Mammals replace their teeth a . Along with tooth changes, jawbones changed roles. Fewer and stronger bones anchored the jaw, which allowed for stronger jaw musculature and led to the mammalian (clench your teeth and you can feel your masseter muscle). Bones previously anchoring the jaw were no longer needed and . The jaw’s rearrangement led to the most auspicious proto-mammalian development: . Mammals had relatively large brains from the very beginning and it was probably initially . Mammals are the only animals with a , which eventually led to human intelligence. As dinosaurian dominance drove mammals to the margins, where they lived underground and emerged to feed at night, mammals needed improved senses to survive, and auditory and olfactory senses heightened, as did the mammalian sense of touch. Increased processing of stimuli required a larger brain, and . In humans, only livers use more energy than brains. Cynodonts also had , which suggest that they were warm-blooded. Soon after the Permian extinction, a cynodont appeared that may have ; it was another respiratory innovation that served it well in those low-oxygen times, functioning like pump gills in aquatic environments.
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Grammar Bytes! :: The Subordinate Conjunction
Did the larger brain lead to the behaviors, or did the behaviors lead to the larger brain? If other evolutionary trends have relevance, they mutually reinforced each other and provided positive feedbacks; down one evolutionary line it reached conditions that led to the human brain. The initial behavior was probably the use of a body part (the brain) for a new purpose, and its success led to selective advantages that led to mutual reinforcement. Although it is by no means an unorthodox understanding, I think that the likely chain of events was walking upright freed hands for new behaviors, which led to new ways of making and using tools, which enhanced food acquisition activities. This allowed the energy-demanding brain to expand, as well as related biological changes, which led to more complex tools and behaviors that acquired and even more energy. That, in short, defines the human journey to this day, which the rest of this essay will explore. There has never been and probably never will again be an energy-devouring animal like humanity on Earth, unless it is a human-line descendant.
The subordinate conjunction has two jobs
Few people on Earth today have much understanding of the relationship between . Most people think that money runs the world, when it is only an accounting fiction. Money by itself is meaningless, and financial measures of economic activity can be highly misleading. I noted long ago that scientists had little respect for . that obscured the role of energy while exalting money. What a coincidence. Understanding this essay's first half will help with comprehending the last half, and the connections between energy, ecosystems, and economics should become clear.