Population Trends. Historians estimate that between 1700 and 1800 the European population increased from 120 million people to 180 million. By the outbreak of World War I in 1914 the European population had reached 458 million people. This population growth occurred despite the rising average age at first marriage (by 1850, twenty-four for women and twenty-seven for men). The increase was fueled by lower mortality rates arising from better sanitation and improved medical and health care. New foods introduced into Europe also helped people live longer. Nutritious and plentiful new crops from the Americas such as corn and the potato were gradually encorporated into the European diet. Farmers improved agricultural techniques as well, increasing crop yields and thus the food supply. Many political leaders believed that large populations benefited their countries economically and militarily. Until the 1850s and 1860s the populations of...