The truth of the scientific (induction) method is that at best, all any interpreter of a science research paper can conclude is that probably Adam and Eve did not exist. The possibility of Adam and Eve exists.
This probably is based on assumptions and estimates some of which may be valid; some may not since hard data going millions years backwards is rare.
The possibility of Adam and Eve is based on the superior quality of their rational souls. It is also based on the rapid expansion of the human population.
The issue of incest between siblings would not come into play because it would take a number of generations for genes to reach the stage where the wrong combination at conception would result in human diseases. Because of the length of female years of reproduction, overlapping generations would occur immediately. Overlapping generations quickly increase the degree of relationship between the man and the woman. Therefore, in a short period of time, incest between siblings would not be needed.
Again, because of their superior intelligence, the first descendants could migrate with a better chance of surving the perils of the environment. Migration would separate groups of descendants, each developing their own characteristics as the anatomy adapted to the surroundings.
When one uses the word possibility for Adam and Eve, it signifiies a strong argument for their existence. When one looks at our own human nature and our relationship with Jesus Christ, True God and True Man, there are no doubts about Adam and Eve’s existence.