I’ve heard, in context with the first theory you mentioned, that since Adam and Eve (Chavvah) were created genetically perfect, their siblings producing offspring would not incur the kind of chromosomal damage that incest causes today at least for a number of generations.
Science these days traces humanity back to a “mitochondrial Eve” and a “Y-chromosomal Adam”; in other words, just two ancestors for all of mankind.
Chavvah for Eve, is the Jewish name for her? Never heard her called that. Thanks for sharing your theory. Just was doing more reading. Jewish accounts say Adam and Eve had 33 sons and 23 daughters of which came the population of the earth.