This is a very old book and is used as a standard reference by the Encyclopedia Britannica. The author seems pretty annoyed to find that ancient Indians had invented of the decimal system and the algebra, thereby laying the foundation for modern mathematics. So, the author veers off into genetics to bring out a novel explanation - hybrid vigor. Crossbreeding between "Aryans" from the West and "indigenous" people of India created a vastly superior race, who were capable of inventions that could last for millennia. He goes on to say that the hybrid vigor lasted only a few generations, which curtailed further development of science and mathematics in India.