7 things about our body that scientists can't explain

The "kissing gene" has not yet been found. As it turns out, not all human societies throughout history did it. Kissing couples are found only in 46% of cultures. In some communities kissing was even considered weird, unclean and disgusting.

At the same time, other animals, such as chimpanzees, kiss. According to one of theories, kissing originally occurred as a way to test potential partner's health through taste. Some scientists also believe that it might have evolved from the practice of a mother feeding her babies through mouth, pushing the food with the tongue.

Still, there is no exact answer to why humans started kissing and showing their affection this way. One thing for sure - we kiss because it feels good.

In evolutionary terms, altruism is actually odd behavior and one of the greatest paradoxes about human mind. It's still unknown if true altruism exists or we just do kind things for others for our own pleasure. Anyway, generosity do make us happier and play an important role in group bonding. Many scientists believe that one day they will be able to scientifically explain the nature of kindness.

According to a new study, it's easier for us to avoid lying and cheating in the morning. Over the course of the day, our ability to subdue our impulses and emotions reduces, so unethical behavior more often takes place in the evening. This phenomenon, called "morning morality effect", was traced in the course of an experiment, but the real reason for such behavior is still unknown.

This well-known feature of our body still can't be fully explained. One of the theories is that our body releases adrenaline when we are worried, which speeds up our breathing and heart rate. This way our organism prepares us to run from danger. Others think that we turn red when we lie to alert others, reveal our weakness and avoid confrontation.

The exact reason for that is unknown. Some scientists assume that twitching before falling asleep may be caused by such factors as stress, tiredness, eating foods rich in bad fats and anxiety.

Others believe that we've inherited this feature from our ancestors who slept on trees. Their brain sent special signals to different parts of their bodies to ensure they would not fall down.

Other animals are not familiar with the unpredictability of the awkward years. Some scientists believe that because of our large brain we need a lot of time to get prepared for adulthood, and adolescence gives us enough time to experiment with our behavior and learn to cope with our feelings.

Humans have found a unique way to express their feelings and spread knowledge. Our ability to create art is based on complex instinctual desires, and they haven't been studied comprehensively yet.