ciple argued that "human society could never progress toward perfectibility because the population inevitably tends to increase beyond the means of subsistence and is kept within the bounds of its resources only by misery, vice, and moral restraint". Malthus' principle of population was based on the supposed differences in reproduction rates between humans (who because of their status as "top dog" in the animal kingdom reproduced "geometrically") and animals and plants (who could only increase "arithmetically", because they served mankind as a means of sustenance). Darwin by contrast, shifted the center of attention from humans to the animal and plant kingdoms, because he was impressed by their enormous natural fertility, which was kept in check only by their own limited means of sustenance. By shifting his perspective from mankind to animals and plants Darwin revealed the basic fallacy of Malthus' argument. For if humans increased geometrically, animals and plants must also increase at the same rate, and perhaps even more, because overall their natural rate of reproduction is higher than that of mankind. Therefore, the struggle for existence, which to Malthus meant that hardship and misery were the defining features of human life, to Darwin meant that every species was in constant change, because nature favored the fittest through the process of natural selection. Three and a half years have passed since Darwin read Malthus in October 1838 before he finally sat down to write his ideas for the Origin formally in May 1842. There are two main reasons for this lengthy delay. First, throughout his life Darwin suffered from ill health, which began to get acute in 1837, and was particularly debilitating between 1838 and 1842. Second, during this time Darwin had more pressing matters to attend to. In particular he was working on the book Coral Reefs, papers for the Geological society, and work connected with the Zoology of the voyage of the B...
