Sexual Selection

Darwin introduced the idea of sexual selection as a complementary to natural selection. In the living world, one sex, usually the female, invests more in reproduction process. She has standards to choose the best males to mate with. On the other hand, males can mate with many females. In order to spread one’s own genes as many as possible, the males compete with each other based on females’ standards in order to win the chance to mate with females.

red deer
Two red deers competing with each other

The picture above shows two male red deers competing with each other. They are trying to show their strength and fitness to attract female. Some female doesn’t choose male based on the strength. For example, peacock. The male peacock that has the most beautiful and incredible tail always attracts a female peacock. Such selection has no apparent relationship with fitness, but “ornaments”. By selecting peacock with beautiful tails, a female will have “sexy sons”, who can pass on her genes in the future.

A male peacock showing his tail

So, has sexual selection influenced the evolution of human? Although there’s not so many academic research to prove it, but it will be doubtful to say no. Some scientists have suggested that our brains are the result of sexual selection. Our ancestors viewed intelligence as one of the standards while selecting partners to mate with, so that we become smarter and smarter during the evolution.



“Unexpressed emotions will never die. They are buried alive and will come forth later in uglier ways.”
― Sigmund Freud

Psychoanalysis is a set of theories related to the study of the unconscious mind. Sigmund Freud, an Austrian neurologist, established the disciplines in the early 1890s.


You must have seen some cartoons like the picture above: a character with a devilish incarnation of him or herself on the shoulder, and an angelic one on the other. According to psychoanalysis, although we can’t see those two little incarnations on our shoulder, we have them in our mind.

Central idea of psychoanalysis is that lots of human desires are beneath the level of conscious awareness. Those desires just spilling over as a neurotic tic occasionally. Also, sex plays a big role in this theory. We tend to deny some of our unacceptable desires with the repression mechanism. Freud believed a common source of psychic conflict comes from sexual fantasies in childhood. The most infamous example is the Oedipus complex, which I will explain in my next weeks’ post.

Critiques points that what psychoanalysis claims are untestable. But there are examples in today’s research showing that repression mechanism do exist.