Homo habilis and his fellows were furtive little scavengers who picked what they could from carcasses that leopards left behind and rounded out their diet with fruits and nuts and roots (see binford, 1981; Brain, 1981). They lived by their wits, and natural selection favored hardware that would permit quick-wittedness. Programmability - and the consequent capacity for extrasomatic adaptation - have made it possible for human beings to advance a very old evolutionary trend at a vastly increased rate. Humans are the most recent in the series of heterotrophs that use increasing amounts of energy, but they differ from other species in this lineup in their ability to use more energy mba without further speciation. Over the course of humanity's short history, greater and greater amounts of energy have been used by the same biological species (see white, 1949, chapter 13). Extrasomatic energy some human innovations have dealt with the fate of energy channeled through metabolic processes. The development of weapons, for example, made it possible to focus somatic energy so as to obtain high-energy foods with much greater efficiency.
Somatic adaptation is like building a hard-wired computer to perform a certain task better than a previous hardwired computer. Extrasomatic adaptation is like writing a new program to perform the task better, without having to build new hardware. The use of language, with its arbitrary relationship between signs and referents, makes possible a wide variety of different software. Programmability - the ability to learn - is not unique with human beings, but they have developed the capacity much further than any other species. Programmability probably developed as an evolutionary response to pressure for paper flexibility. The ability to make use of a variety of different resources runs deep in the human background, for placental mammals arose from ancestral forms in the order Insectivora that presumably ate insects, seeds, buds, eggs, and other animals. When our hominid ancestors came down from the trees to exploit the African savannas, flexibility was again advantageous.
This is the natural context of Homo sapiens, the most energy-using species the world has ever known. The human animal the extent of human energy use is a consequence of the human capacity for extrasomatic adaptation. This capacity makes it possible for human beings to adjust to a wide variety of novel circumstances without having to wait many generations for evolution to change their bodies. A comparison of somatic and extrasomatic adaptation will show just how remarkable an ability this is: If longer, sharper teeth are adaptive for a predator, animals with teeth that are slightly longer and sharper than those of their fellows will have a slight reproductive advantage. In contrast, a human hunter can imagine a longer, sharper arrowhead; he can fashion it with nimble hands; and if it is really more efficient than the short, blunt arrowheads that everybody else has been using, his peers will soon adopt the new invention. The chief difference between the two means of adaptation is speed: Humans can adapt, relatively speaking, in a flash. Extrasomatic adaptation is possible because humans are, in the idiom of the computer age, programmable.
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Carbon dioxide (of which there was an abundance in the earth's early atmosphere) reacts with water through energy from light, fixing carbon and releasing oxygen, and a portion of the energy remains captive as long as the carbon and the oxygen remain apart. Plants release this energy when and where necessary to conduct their metabolic business development (Starr taggart, 1987). As time passed, the sheer bulk of life increased, so that more and more energy was, at any given time, stored in living matter. Additional energy was stored when carbon from once-living matter was buried, in ever-so-tiny increments, under the surface of the earth-in deposits that became coal, petroleum, and natural gas as well as in sedimentary rocks containing calcium and magnesium carbonates derived from shells. Of all the carbon that has played a part in the life process, very little was separated out and held apart in this way, but over the course of millions and millions of years, it has mounted. More and more carbon wound up under the ground, with a greater and greater amount of oxygen in the earth's atmosphere.
This separation of carbon and oxygen from a primeval atmosphere in which carbon dioxide and water were abundant represents a vast accumulation of solar energy from the past. Life evolves to exploit every possible niche, and as autotrophs developed better ways to capture and store the sun's energy, heterotrophs developed better ways to steal. Independent locomotion was adaptive in the search for nutrients, although it took a little more energy than being buffeted about by the elements. Cold-blooded fish and amphibians were followed by warm-blooded species, which reap the benefits of remaining active at lower temperatures, while using yet more energy in the process. The development of predation opened access to a supply of high-energy food with a further energy investment in procuring. Throughout the history of life, as increasingly dense reservoirs of energy became available, species that made use of increasing amounts of energy evolved (see simpson, 1949,.
But science has found no such balance. According to the second Law of Thermodynamics, energy flows from areas of greater concentration to areas of lesser concentration, and local processes run down. Living organisms may accumulate energy temporarily but in the fullness of time entropy prevails. While the tissue of life that coats the planet Earth has been storing up energy for over three billion years, it cannot do so indefinitely. Sooner or later, energy that accumulates must be released.
This is the bioenergetic context in which Homo sapiens evolved, and it accounts for both the wild growth of human population and its imminent collapse. Energy in evolution we are caught up, as organic beings, in the natural process through which the earth accepts energy from the sun and then releases. There has been life on Earth for at least three and a half billion years, and over this time there has been a clear and constant evolution in the way energy is used. The first living things may have obtained energy from organic molecules that had accumulated in their environment, but photosynthetic autotrophs, able to capture energy from sunlight, soon evolved, making it possible for life to escape this limited niche. The existence of autotrophs made a place for heterotrophs, which use energy that has already been captured by autotrophs. It is not clear how photosynthesis got started, although it is a combination of two systems that can be found singly in some life forms that still exist. But blue-green algae, which are among the earliest organisms documented in the fossil record, already employed the two-stage process that was eventually handed down to green plants. This is a complex sequence of events that has a simple outcome.
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Unfortunately, worldwide implementation of a rigorous program of birth control is politically impossible. Conservation is futile as long as population continues to rise. And no resources are truly renewable. 2 The environment, moreover, is under no obligation to carry a constant population of any species for an indefinite period of time. If all of nature were in perfect essay balance, every species would have a constant population, sustained indefinitely at carrying capacity. But the history of life involves competition among species, with new species evolving and old ones dying out. In this context, one would expect populations to fluctuate, and for species that have been studied, they generally do (ecology texts such as Odum, 1971 and Ricklefs, 1979 give examples). The notion of balance in nature is an integral part of traditional western cosmology.
Ever since malthus, at least, it has been clear that means of subsistence do not grow as fast as population. No one has ever liked the idea that famine, plague, and war are nature's writing way of redressing the imbalance - malthus himself suggested that the operation of "preventive checks which serve to reduce the birth rate, might help prolong the interval between such events (1986. 1 And in the two hundred years since malthus sat down to pen his essay, there has been no worldwide cataclysm. But in the same two centuries world population has grown exponentially while irreplaceable resources were used. Some kind of adjustment is inevitable. Today, many people who are concerned about overpopulation and environmental degradation believe that human actions can avert catastrophe. The prevailing view holds that a stable population that does not tax the environment's "carrying capacity" would be sustainable indefinitely, and that this state of equilibrium can be achieved through a combination of birth control, conservation, and reliance on "renewable" resources.
grow through the use of extrasomatic energy. But the exhaustion of fossil fuels, which supply three quarters of this energy, is not far off, and no other energy source is abundant and cheap enough to take their place. A collapse of the earth's human population cannot be more than a few years away. If there are survivors, they will not be able to carry on the cultural traditions of civilization, which require abundant, cheap energy. It is unlikely, however, that the species itself can long persist without the energy whose exploitation is so much a part of its modus vivendi. The human species may be seen as having evolved in the service of entropy, and it cannot be expected to outlast the dense accumulations of energy that have helped define its niche. Human beings like to believe they are in control of their destiny, but when the history of life on Earth is seen in perspective, the evolution of, homo sapiens is merely a transient episode that acts to redress the planet's energy balance.
Studies, volume 16, number 4, march 1995,. Human Sciences Press, Inc. Life on Earth is driven by energy. Autotrophs take it from solar radiation and heterotrophs take it from autotrophs. Energy captured slowly by photosynthesis is stored up, and as denser reservoirs of energy have come into being over the course of Earth's history, heterotrophs that could use more energy evolved to exploit them, homo sapiens is such a heterotroph; indeed, the ability to use. The control of fire and the exploitation of fossil fuels have made it possible for, homo sapiens to release, in a short time, vast amounts of energy that accumulated long before the species appeared. By using extrasomatic energy to modify more and more of its environment to suit human needs, the human population effectively expanded its resource needed base so that for long periods it has exceeded contemporary requirements.
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A major problem with the use of fertilisers occurs when they're washed off the land by rainwater into rivers and lakes. The resulting increase of nitrate or phosphate in the water encourages algae growth, which forms a bloom over the water surface. This prevents sunlight reaching other water plants, which then die. Bacteria break down the dead plants and use up the oxygen in the water so the lake may make be left completely lifeless. The increase of nitrate or phospate from fertilisers into water causes eutrophication. Now try a, test Bite. Energy and Human evolution click here, please address correspondence. Price, 254 Carpenter Hall, cornell University, ithaca, ny 14853. From Population and Environment: a journal of Interdisciplinary.