How old was Adam and Eve when they conceived? And what is their lineage?
We do not know how long they were in the garden until sin occurred. We do know it was after they were banished that they began to fulfill the command to be fruitful and multiply. No data is given from which we can exactly determine the duration of their residence in the garden of Eden, it is impossible to form any opinion as to what the length of time was but we do know when their third son was born.
Gen 5:3 And Adam lived one hundred and thirty years, and begot a son in his own likeness, after his image, and named him Seth.” So Cain and Abel were born sometime before this.
What we have are examples of Adams offspring’s and those born to them afterwards. For Cain:
Gen 4:17 And Cain knew his wife, and she conceived and bore Enoch” There is no dates for the ages of how old he was when this happened, we can only estimate it between the other births.
Gen 4:18: To Enoch was born Irad; and Irad begot Mehujael, and Mehujael begot Methushael, and Methushael begot Lamech.”
There are no dates for the lineage of Cain who is not part of the lineage of the Messiah which the bible concentrates on. Daughters are not mentioned (only of Cain). In Gen.5 the first male born in the family is mentioned by name in the genealogy.
Lineage of the Messiah that would come through Noah.
What is often referred to as the Ungodly Line of Cain would be better translated the lineage that does not bring the Messiah Gen. 4:16–24.
The Godly Line of Seth should be called the lineage of the Messiah 4:25–5:32, which is referred to in Luke 3:38 as it is traced backwards to the son of Enos, the son of Seth, the son of Adam, the son of God." It was through this line that the Messiah would be born. 1 Chron. 1:1-4 we have the chronology of Genesis. “Adam, Seth, Enosh, Cainan, Mahalalel, Jared, Enoch, Methuselah, Lamech, Noah, Shem, Ham, and Japheth.” Christ is the Seed of the woman (3:15), from the line of Seth (4:25), the son of Shem (9:27), the descendant of Abraham (12:3), of Isaac (21:12), of Jacob (25:23), and of the tribe of Judah (49:10).
Gen 5:6 Seth lived one hundred and five years, and begot Enosh.
Gen 5:9 Enosh lived ninety years, and begot Cainan.
Gen 5:12 Cainan lived seventy years, and begot Mahalalel.
Gen 5:15 Mahalalel lived sixty-five years, and begot Jared.
Gen 5:18 Jared lived one hundred and sixty-two years, and begot Enoch.
Gen 5:21 Enoch lived sixty-five years, and begot Methuselah.
Gen 5:25 Methuselah lived one hundred and eighty-seven years, and begot Lamech.
Gen 5:28 Lamech lived one hundred and eighty-two years, and had a son. (Noah)
Enoch’s son Methuselah became the oldest man we have on record, nine hundred and sixty-nine years (Gen. 5:27) It wasn’t until Lamech Methuselah son, that the lifespan dropped under 800 years. Lamech lived to seven hundred and seventy-seven years (Gen 5:31).
Gen 5:32 And Noah was five hundred years old, and Noah begot Shem, Ham, and Japheth.
It appears Noah didn’t have his first son until he was 500 years old; imagine that.