In 1 Corinthians 11, Paul tells women they need to wear head coverings for two reasons: (1) “Because of the angels,” and (2) because long hair is a woman’s glory. On the other hand, long hair for men is a disgrace and they are supposed to have short hair. What on earth is going on here?
The first part about the angels has to do with Genesis 6, where angels are said to have once procreated with human women to create the race of the giants found all throughout the Old Testament. Since angels had crossed the line with humanity in the past (and since angels were thought to be present when we worship), Paul wanted to keep angels from crossing the line again by having women cover their hair when they gathered for worship.
But why the heck would a head-covering settle down the angels? Bible scholar Troy W. Martin proposes that the answer lies in old scientific thought. According to ancient medical journals, both men and women were thought to have semen in their brains and hair was thought to be a vacuum that brought semen towards it. After the semen dried, people’s hair would then be longer. This is why they thought men had more body hair—their body hair was vacuuming the semen to where it belonged (hence why Paul thought it was a disgrace for men to have long hair, as they would then be keeping their semen up in their brains where it didn’t belong). Conversely, women had long hair because they needed the extra strength to pull semen up into their womb after intercourse.
So why did Paul think women should wear head coverings in church and that “nature itself” taught us all of this? Well, to quote him directly, “her hair is given to her for a ‘peribolaion’.” Most English translations of the Bible turn the Greek word “peribolaion” into “covering,” but other ancient Greek texts translate this word as “testicles.”
So in other words, Paul thought women should cover their private parts when they gather because (1) that’s what you do when you’re in sacred space (just like the Old Testament law required) and (2) so that angels aren’t tempted. Paul’s intention is right based on the way his culture thought, but since all of this science is completely wrong, a woman’s hair is obviously not inappropriate to be displayed in church or a temptation to the angels.