On September 2nd 1939, when the British Empire declared war on the German Empire (thus ensuring we would have another world war), there were two main scientific theories predicting the shape of our world at the war's end.
The far more popular theory at the time was called Modernity, Social Darwinism or simply 'Might is Right'.
It said Evolution was a vertical affair, with wiser and more mighty entities inevitably and naturally replacing entities that were weaker and more foolish.