How did global networks of exchange impact chinese society in the yuan dynasty?

Who did the first work in creating vaccines

Someone who accepted the beliefs of social darwinism would have also agreed with which of these statements?

Which suggests the most critical aspect of the peak oil theory? 1) controversy rages over rumors that the fracking lobby in washington has influenced the statistics. 2) supporters and critics argue endlessly over the rate of extraction and shape of the bell curve. 3) saudi arabia will soon have to begin fracking, leading to protests and further destabilization. 4) a new oil discovery means a fresh peak cycle, making that region the target of aggressors.