A couple of things worth noting:
- Kenan and Cain could be translated to be the same word.
- Enoch walked with God for 300 years. When he was 365 God took him and he did not face death.
- Lamech was the father of Noah.
Most of those listed in the lineage before Noah had children earlier in their lives, however Noah didn't have children until he was 500 years old. One thought is that Noah saw the sinful nature of the times that he lived in and did not want to father children.
We later read of divine beings taking wives from the daughters of men. We read of the Nephilim, a race that were giants. Perhaps there was a race of superhumans? That is only speculative.
"The Lord saw how great was man's wickedness and how every plan devised by his mind was nothing but evil all the time." So the Lord decided to blot out man and all the beasts that he had created for He regretted making them. However He found favor with Noah."
By this time, Noah had three sons. Ham, Shem and Japheth.