Sibling rivalry

My regular readers know I hold no sympathy for wusses. My sentiment extends to schools that generate wusses such as Waldorf and Montessori.

I argue that I am looking at the empiric world and the nature of human beings when I conclude that wusses are unnatural and probably semi-human.

When two children are born to the same mother within a 2 1/2 year period, the default relationship between those two children is sibling rivalry.

Why? This is true even in societies that heavily suppress conflict, such as the Japanese and the Balinese.

Why is sibling rivalry the default behavior of children close in age from birth until the pair is age 18? Siblings are always fighting, tormenting each other and ‘carrying on’.

I assume it is to give both of them a better chance of surviving in a Darwinian real world.