New Defender's Study Bible Notes
4:14 every one. Adam had daughters as well as sons (Genesis 5:4), and brother/sister marriages were necessary at least in the first generation, before the accumulation of genetic mutations could make such close marriages genetically dangerous. Since the antediluvians lived for hundreds of years and since they could propagate children for hundreds of years (note Genesis 5:15,32), the population multiplied rapidly. This concern of Cain’s, therefore, was quite realistic. Since Cain could not produce his own food, he would have to purchase it from others, but other people would naturally tend to fear him and try to avoid him or even to do away with him.