of extinct animals in Argentina he noted that their remains more closely resembled those of contemporary South American mammals than any other animals in the world. He noted "that existing animals have a close relation in form with extinct species", and deduced that this would be expected "if the contemporary species had evolved form South American ancestors" not however, if thereexisted an ideal biota for each environment. When he arrived on the Galapagos islands (islands having been formed at about the same time and characteristically similar), he was surprised to observe unique species to each respective island, particularly tortoises which possessed sufficiently differentiated shells to tell them apart. !From these observations he concluded that the tortoises cou ld only have evolved on the islands32.Thomas Robert Malthus was an English economist and clergyman whose work An Essay on the Principal of Population led Darwin to a more complete understanding of density dependent factors and the "struggle in nature". Malthus noted that there was potential for rapid increase in population through reproduction - but that food cannot increase as fast as population can, and therefore eventuality will allow less food per person, the less able dying out from starvation or sickness. Thus did Malthus identify population growth as an obstacle to human progress and pedalled abstinence and late marriage in his wake. For these conclusions he came under fire from the Enlightment movement which interpreted his works as opposing social reform33.Erasmus Darwin, grandfather of Darwin, was an unconventional, freethinking physician and poet who expressed his ardent preoccupation for the sciences through poetry. In the poem Zoonomia he initiated the idea that evolution of an organism results from environmental implementation. This coupled with a strong influence from the similar conclusions of Lamarck shaped Darwin's perception on the environment's inherent...
