Thomas Jefferson, who wrote the Declaration of Independence, cited figures like Locke as some of mankind's best thinkers. So at this early date, nations were at least writing these types of words into their Declarations of Independence, into their Constitutions. But despite that, the 20th century is one of the bloodiest centuries in human history. You have World War I, where roughly 17 million people die. In World War II, 50 to 80 million people die, some directly because of the conflict, but many because of lack of access to food and famine. The Chinese are particularly hit. Over 15 million died during the Japanese occupation of China.