The title statement above is my opinion; it is not something that I can prove conclusively. However, allow me to share why I believe that to be the case.

The Bible gives us very little information from before the flood. We don’t know when Lamech and his sons were born or when they died. I think they died before the flood because two of the hints the Bible does give us point that direction, while one of the hints may point the other direction, depending on how you interpret it.

We are told clearly that Cain was building a “fortified place,” (Gen 4:17). I assume that means he was building it with strong materials such as stones, and that he was trying to grow his population faster than the rest of Adam’s descendants through Seth. In that way, Cain could outnumber the relatives that excommunicated him, if there were ever a battle.

If we look at the genealogy of Seth and the short list of Cain’s descendants, there were only six men mentioned in Cain’s line while eight are mentioned in Seth’s line, the last one being Noah. Some have concluded that the line of Cain had children at a slower rate than did the line of Seth. They conclude this by dividing the total time until the flood by the number of generations we are given for Cain’s line.

The brief genealogy of Cain’s line in Gen 4:17-18 reads very differently than the full genealogy of Seth in Chapter 5 of Genesis. This may be to place emphasis on Seth’s line, or because the part about Cain’s line was never intended to fulfill the same purpose, i.e. to take us all the way to the flood. I think it is the latter.

I think that the Bible never intended to give a full genealogy of Cain’s descendants from Cain till the flood, rather we have a short list that takes us to Lamech and three of his sons (he surely had more than three) and then stops. The fact that we have more details about those four men than anyone else between Adam and Noah tells me that Lamech and his sons (and one daughter) were very important influencers. Otherwise, their names would not have been mentioned and we would have no details about them.

 When Gen 6:4 says  “The Nephilim were on the earth in those days (and also after that),”  I take it to mean that there were a number of ruthless tyrants ruling kingdoms of their own just prior to the flood. This would mean that the kingdom that Lamech and his sons had created fell apart after Lamech’s death, or after the death of his sons. It could have been his three most powerful sons that tore the kingdom apart. After them, others wanted to do what Lamech had done; they wanted to rule the world. So it became a fight in which all the powerful, ruthless giants tried to become greater than their rivals, and the common people were caught in the crossfire.

Therefore, the two things that point to Lamech and his sons being dead by the time of the flood are that Cain was building a fortified place in part by growing his population faster than Seth, and secondly that by the time of the flood there appear to have been a number of large, ruthless tyrants ruling over as many of the people and as much of the land as they could. On the other side of the coin is the one fact that we have a shorter list of descendants in Cain’s line. If that list is intended to be complete, then yes, they were having children at a slower rate and Lamech and his sons were still alive when the flood came. But I don’t think it was intended to be a complete list.

From my estimates on when Lamech and his sons were born, and considering their length of life to be similar to that of the descendant of Seth that were born about the same time (but not in the same generation), I come up with years of death being year 1235 after creation for Lamech and around year 1290 after creation for Jabal, Jubal and Tubal Cain. We can also look at it in years prior to the flood, in which case the year of death for Lamech would be 421 years before the flood and for his sons about 366 years before the flood. If my assessment is right, none of them were alive or ruling over a kingdom when the flood came.

Noah knew these men, or knew of them, because he was born about 179 years before Lamech died, if my estimations are correct.

Why is this information important?

This fits perfectly with the picture I paint of what was going on just before the flood as described in Genesis 6:1-4. I recommend you go and read The Beginning of the Wickedness that Necessitated the Flood or jump right to Everyone Sought the Advantage.