Some researchers argue that modern life is less violent than life in our evolutionary past because we have increasingly redefined the boundaries of the in-group. what fact best supports this claim?

People who live in America can simply call themselves American now, as opposed to earlier when the area was divided into various countries.

Explanation:

This fact is the best out of the options that fits the description of the singular fact that best supports thee claim of modern life being less violent as compared to more and more of our evolutionary past.

This fact states that the people who were earlier divided into the countries and lived in a constant state of war, are now able to live together in a peaceful manner, thus stepping up from their evolutionary past and becoming less violent as they step into an era of modernization.

hygrometers and hair thermometers (often found as part of hygrometers/psychrometers) can be used to measure humidity. barometers are used to measure atmospheric pressure, while anemometers are used to measure wind speed. so the 2nd and 4th choices should be the correct answers.