Primogeniture in northern Europe:

So I should be writing a paper right now. Yes, right this minute. But it's not due till Wednesday (afternoon, no less) and if I didn't have a midterm Wednesday and code due Thursday, I wouldn't have even started it.

I'm writing about changes in Norse society as a result of Christianization and so far I'm looking at concepts of marriage and inheritance. It's been making me wonder about primogeniture, though. Where does it come from? I mean, I know in England and Ireland at least it's the legacy of the Normans, and William the Conqueror really hated to be called William the Bastard and all that, but why did William choose to install this system? It doesn't seem natural at all to me. Were the Normans in France known for their rigid system of primogeniture? I can't imagine they were, since a bastard was able to become Duke of Normandy.

It seems to grow out of a system of scarce land, or at least land with scarce resources. If the land is barely able to support one man, dividing it among several sons is suicidal. But why would the Normans implement such a system just when they are getitng a whole new island to divide among their sons?

And why wouldn't this system have caught on in a resource-poor Norway much earlier than it actually did? There is obviously something else going on there.