1. Oasis Theory. Proposed in 1908 by Raphael Pumpelly, an American geologist and explorer, this theory is predicated on climatic change as the basis of the start of agriculture. Due to dry spell, both humans and animals converged close to oases. It was there that animals were first domesticated (put under the management of man) and seeds were planted. However, this theory finds opposing views because climatic data do not support it.