Fisher's principle

Fisher's principle tries to explain the commonly observed sex ratio in many organisms, including homo sapiens. (Approximately 1 to 1 ratio) Explaination: 1, Suppose initially, that male is the abundant sex. Due to this difference, a female have more mates compared to a male, thus the female sex have greater fitness. 2, Parents have the control over the biological sex of her offspring. Due to the fact that a female have a greater fitness in the population, mothers will give birth to more females. 3, Eventually, the uprising of the female sex will cause the equal sex ratio. The equal sex ratio will cause equal fitness of the two sexes, and an equal number of male and female babies will be born.