Sex taboos

a brief and incomplete tour: here

"In some societies, sexual activity is prohibited during certain times of day. The Cuna of Panama approve of sexual relations only at night in accordance with the laws of God. The Semang of Malaysia believe that sex during the day will cause thunderstorms and deadly lightening, leading to drowning of not only the offending couple but also of other innocent people. And the West African Bambara believe that a couple who engage in sex during the day will have an albino child."

They believe...

or is this just the conventional and formal explanations for why they do what they do? And if so, can we legitimately say that these are the things that they believe? Begging the question of "believing" something...