According to the British journal Nature, the human penis ever had thorns. The study was conducted by American universities of Stanford, Georgia and Pennsylvania. Research indicates that the same molecular mechanism that made the man lose the spines of the penis would also have led to the growth of the male brain.
According to scientists, the thorns of human penis had a dual function: to give more sensitivity to the man in the sexual act and remove the sperm of rivals that had previously mated with one female. The spines were small flexible structures of keratin, but hurt the women of the caves. The evolution was providential.