What about DNA corruption by interbreeding, incest, inter family pedophilia and pedogogy.?. Can't be good for the gene pool.. and spread to succesive generations geometrically..
Pedagogy?
Pedagogy n. 1. the function, work, or art of a teacher; teaching. 2. instruction.
Are you referring to these 40-year-old blond teachers picking on students in Catholic schools, or what?
While harmful genetic traits are certainly magnified by inbreeding so are positives traits. This is why dogs or farm animals become overbred. If you want to breed a certain trait often animals most closely related share those traits.
In the case of early humans this kind of inbreeding would create "better" human traits. At the same time passing along the negative traits would tend to lead to the death of the offspring so there would be no harm to the gene pool.
That's why any one pregnancy from an outside group will, over a few generations, strengthen the entire tribes gene pool.