Before, when human females moved on four "paws", males could perceive when they were in heat or in need. Their buttocks inflated  and took a characteristic reddish color.  But when de first humans started to stand on their legs, the genitals became hidden. Because they couldn't see the buttocks any longer, the male's interest shifted to what they saw that was mostly prominant: the udders. Bosoms have become the prviledged element of erotic attraction. But, not watching directly the female sex, the first male humans didn't know anymore when the female felt "physiogically" the desire of union. Then, the males took the habit to call for coupling anytime.  Even though the female shouldn't exprience a compelling desire before the fourteenth day, during ovulation.

 

The biped position modified the feminine behavior but also the masculine one. Before, in the quadruped position, the male could hide in the shadow of his belly the reality of his desire, once standing, the masculine desire became "verifiable".

 

Inside the first human community, this display of sexual desires of everyone at the sight of everyone was hard to manage.That is why the first clothings were loincloth before being used for protection against cold and rain. Laws were established in these first communities in order to prohibit incest and socially disturbing unions (like taking over the female of the dominant chief).  Speech will allow to regulate the relations and authorize each and every one to explain their intentions in the society.

This is probably the time where must have appeared the expressions "I love you" which means " You probably do not see it because of my loincloth, but I am experiencing a strong desire for you." The expression have ever since been a bit changed...

 

The human male, like all animals, should only feels a sexual arrousal of 3o seconds. Bit, he has developped a sort of pathology with the power of his will, by constainning it to last longer. En then man has evolved and he has become better to master this behavior that goes "against nature."