While beards have gone in and out of fashion in different societies over the years, there are religious denominations, including Sikhs, Muslims, the Amish and sects of Judaism, that encourage or require men to have facial hair. The reason for the requirement is fairly simple, according to Slate's Brian Palmer: to promote masculinity.
In some religious traditions, facial hair fashions were also used to distinguish members of one faith or culture from another. The ancient Israelites, for example, are often depicted as bearded, while the Philistines were clean-shaven. Similarly, early Muslims were directed to trim their mustaches and beards a certain way to distinguish themselves from Christians.
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