Benjamin Franklin had given Malthus the idea that if there were no limiting factors one species could have covered the whole planet and if this was not the case it must be because the various animal and vegetal species were in some way in conflict with each other. Malthus continued to develop this idea. Those who survived would be those who had acquitted themselves the best in this struggle. Thus Darwin finally found the mechanism which he had been seeking - the survival of those individuals the most adapted to the struggle determines evolutionary change. Man is an animal who has descended from other, older species.
All species evolve.
The process of specialisation comes from environmental adaptation. Some time later, in 1862, a young prince and officer in the Tsar's army, Peter Kropotkin, set off for Western Siberia and the North of Manchuria with a body of Cossacks from Amur. The five years that he would spend in this desolated area were dedicated to producing physical maps of that part of Asia correcting the cartological errors of Humboldt with reference to the mountains and rivers. Later, on behalf of the National Geographic Society, he was to investigate the glacial deposits in Finland from which he would deduce his theory that the last ice age covered Europe more comprehensively than had previously been thought. This discovery was his greatest scientific pride.