There's Something About Monogamy...

Monogamy is perhaps nothing more than a lifestyle choice. It is a part of nature, but there is nothing 'natural' about monogamy. The existence of fighter/blocker/killer sperm seems to point to this.

The fighter/blocker/killer sperm exists for the sole purpose of preventing competition from impregnating the egg. Research indicates that 90% of the sperm is fighter/blocker/killer sperm. (Only 10% is designed to fertilise the egg.) This is also referred to as 'sperm competition'.

The fighter/blocker sperm builds a barrier in the cervix area, a barrier that does not allow sperm from a competing male to make it to the ovaries.

The killer sperm neutralises sperm from a competing male.

This scenario, of fighter/killer sperm fighting and killing each other over who impregnates the egg reminds me of jealous lovers fighting and killing each other over the woman..

Jokes apart, it is clear that nature has built into us mechanisms that are designed to ensure that a woman does not get impregnated by two males simultaneously.

Sounds like nature has given us the go-ahead to lead polyandrous/polygamous lifestyles, by offering this biological mechanism!

(Though this mechanism is not foolproof and there have been cases, although rare, in which human females have given birth to twins fathered by two different males.)

I read somewhere that just half a spoonful of semen is enough to impregnate a very large number of women. Perhaps this is a pointer that says men are allowed to get sexual with as many women as they want.

So:

1) Nature protects twins from being fathered by different fathers.

2) Nature has given the power to the male to impregnate a large number of women.

Current Hypothesis:

All lifestyle choices, polyandry, polygamy etc. are equally valid in the eyes of nature. Monogamy is just a choice, not the default.