[allmendream]

They didn't evolve independently. That should be your first clue. Secondly two parent reproduction was favored by natural selection because due to the increased genetic diversity that results.

The things you think you know about what evolutionary biologists know, just aren't so.

[LiteKeeper]

And if you believe that, I have a bridge to sell you!

Current documentation on this issue says that is one of the great puzzles of biology...your explanation is overly simplistic, and does not explain anything. Sorry.