I've thought about this for a wile now. So the first humans, Adam and Eve had two sons. Cain killed his brother then left taking a wife... ... ... ... So that means, them being the first humans, that Cain had to marry one of his sisters that came later. This must have happened a few times with Adam and Eve's children. Then with close cousins after and until they got the population up and growing. A couple of girls that were of Cain's decendants even got their father drunk so they could 'lay him' and have kids of there own to help populate because there weren't enough men on the earth yet. I would just like to hear everyone's thoughts on the subject of these first several years when Adam was alive.