The fascinating thing about this story is not that there are still mysteries about human behavior but rather that some people are not embarrassed by the possible explanations that they offer for them. Anyway, when you assume that everything about us somehow enhances our sex appeal or our survival I guess you're bound to come up with theories like some of the ones below.
If we're looking for an evolutionary explanation for human behaviors it seems to me that many of these are much more likely to be behaviors that supervene upon other genetic adaptations. There's no reason to think that they have any survival value in themselves.
But if we're not looking for evolutionary explanations it could be that the Creator simply gave us laughter, altruism, and art because they make life richer, more human, and less brutish.
Here are some of the "mysteries" discussed in the article:
Blushing: Charles Darwin struggled to explain why evolution made us turn red when we lie, which alerts others. However, some think it may help diffuse confrontation or foster intimacy by revealing weakness.
Laughter: mood-improving endorphins are released when we laugh, which seems an obvious reason to do it...
Kissing: the explanation for kissing is unlikely to be genetic as not all human societies do it. There are theories that it is associated with memories of breastfeeding and that ancient humans weaned their children by feeding them from their mouths, which reinforced the link between sharing saliva and pleasure.
Picking your nose: the unappealing but common habit of ingesting 'nasal detritus' offers almost no nutritional benefit, so why do a quarter of teenagers do it, on average four times a day? Some think it boosts the immune system.
Altruism: giving things away with no certain return is odd behaviour in evolutionary terms. It may help with group bonding or simply give pleasure.
Art: painting, dance, sculpture and music could all be the human equivalent of a peacock's tail in showing what a good potential mate someone is. However, it could also be a tool for spreading knowledge or sharing experience.
Body hair: fine hair on the body and thick hair on the genitals is the opposite of what occurs in primates, our close animal relatives. Suggested reasons for pubic hair include a role in radiating scent, providing warmth or even protecting from chafing.
Superstition: unusual but reassuring habits make no evolutionary sense; however, ancient humans would have benefited from not dismissing a lion's rustle in the grass as a gust of wind. Religion seems to tap into this impulse.
Perhaps, but if superstition is believing in causes which are totally inadequate to the effect then what would we call the belief that all of these behaviors must be produced by genetic mutation? Unguided mutations over time degrade the specificity of information, they don't enhance it. The belief that mutations actually increase the information content of the genotype is, well, a superstition that biologists certainly tap into.
RLC
