Perfect example. Thank you.
The plain reading of the bible is that All men are descended from Adam, because All men die and all men need salvation.
If there were men living before Adam they would not be affected by Adams sin and so die or need salvation.
It is only through Adams decendants that die and need salvation,
As for proof, who ever makes a claim has to provide evidence.
The plain reading is correct. As was pointed out, the Bible follows genealogical descent, not genetic descent. Again, S. Joshua Swamidass proves in his book that by the time of Christ all men would have been descended from Adam regardless of a pre-Adamic population. That doesn’t prove or disprove anything. For additional proof, ask Cain’s wife.