Wait a minute ......
Could It be that engineers are trying to breed female engineers cause there is no ones left?
Was earth a breeding ground for. Fertile female engineers?
So apart from using the xeno as a redbutton auto destruct meganism for seeded worlds ? What if Shaw was the first female the engineer saw? What about when he picked her up ? If he (Bob) was the engineer from another faction trying to prevent the engineers from breeding females? Was that why was so enamoured by looking at magazines ? He's never seen our world as he is from another faction sent to prevent the engineers from harvesting females and then destroying all creatures and man?