The bible states that God created man 'in His own image', male first then the female from a part of the male. Contrary to popular belief the bible makes clear that Adam and Eve had many children (though we are only given the names of the first 3 sons). They mated with their sisters which was all part of God's original plan but, when the earth had quite a large population He instructed them to cease mating with 'close' relatives as there was, by that time, far more choice. That was to prevent any diseases being duplicated by two very close people passing on a double dose of any health issue. If some prefer to invent their own idea of how things happened so that they can leave God out of their scenario then that is what they'll do and, in so doing, will miss all the joy that is experienced by those of us who worship a mighty God who created all things and all life forms.