Just how many times I must hear this ugly statement?:
 

The West (read The Church) has encontered many problems, now after 2000 years their scientists are returning to quran and seeing that men are naturally polygamous.

  As a side note let me first invite Dr. Hovart and many others of her mind to see how dangerous is confusing Christianity with The West. How many people are lost just because they couldn't tell the difference between a St. Francis Xavier and a "blue-eyed colonizer"!
   Returning to the topic, the first thing I wonder is about those "scientists". who are they? Are they the same ones who advocate perfect nudity and child sɛҳuąƖity saying it is healthy and beneficial? The same ones who say that traditional masculine roles damage men? those against wine and animal meat? Those who consider chastity a mental illness????
  But moslems are taking advantage of these "findings" not knowing that some other scientist might have many atheistic or anti-islamic claims.
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   Polygyny and polyandry are both sins. But the reason the first one is tolerated is that it perhaps has less damage (children will know their father).
But it is a falacy:
   If A has less damage than B then A is lawful.
A has less damage.
So it is lawful.
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Killing a child has less bad effect on the society than killing a king. So killing a child is lawful.
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Even if men have greater capacity for infidelity, it doesn't make it lawful. I can have greater capacity for lying, stealing etc. it doesn't mean that I have right to do them. does it?

  But Abraham took his sister as wife, later God forbade it at the time of Moses. So no one can convince a priest to let a brother and sister marry just because Abraham did it.

  What you are pointing to is the tendency we all have to sin and the fallen nature's speciall weakness to keep purity.
   But what they are trying to approve is polygamous nature for men which although it seems great at the first sight for some men, it is in fact ugly in reality.
   For women in non-christian cultures, the whole married life is spent in fear of a co-wife. Some check their men's cell phones, phone their office 10 times a day, pay strict attention to the time of his coming and going etc. etc. to make sure that no other woman is there.
  They feel responsible for it and try to prevent it by doing harmful things like this:
A woman whom I knew was married to a handsome man and had 4 or more children. She was so afraid of a co-wife that she followed her man everywhere he went. Her children grew up without any proper attention and care because their mother had nothing to do but to wear much make up and attend the man in every meeting, party and gathering etc. Her children were really miserable being left without any supervision. When after many years the man died, she came to herself and felt guilty for going outdoors with immodest dress and heavy make up.

You should point out that the quote "from the beginning it was not so." was from Our Lord.

Yeah, that's pretty lazy of me Matthew.  Thanks for pointing that out.