DevilsAdvocate writes:
How do you know Adam and Even were not 20, 30, 40, 50, 60, etc years old when they had children.
The account says they had intercourse AFTER they left the garden and cain was born. Sometime thereafter they had Able. They also had some daughters but by the age of 130yrs, the account says that Seth, the 3rd son was born.
We know that Seth came immediatiatly after Able becasue in Genesis 4:25 its says that after the death of Able, Eve had another son whom she said was appointed in place of Able.
"And Adam proceeded to have intercourse again with his wife and so she gave birth to a son and called his name Seth, because, as she said: God has appointed another seed in place of Abel, because Cain killed him.
So this shows that Adams sons began with Cain, Able then Seth. And we are told that Adam was 130yrs of age when he had Seth.
Genesis 5:3 "And Adam lived on for a hundred and thirty years. Then he became father to a son in his likeness, in his image, and called his name Seth"
For arguments sake im willing to say that they were 50 when they left Eden. They had no children in Eden so Cain was born when Adam was maybe 52 yrs old. There are 80 years before Seth the 3rd son is born as Genesis says Adam was 130yrs old.
Now how likely is it that out of all the children they could have had in 80 years, only 3 were male? Its highly unlikely that all the other children were girls. And in 80 years he could have had 40 children, thats 1 every 2 years.