Ok if Eve and Adam were the first two and only humans on the planet, they made more humans with their children.
The only humans that existed on the planet were Eve, Adam and their children.
Who did their children have sex with to make more humans?
If Eve, Adam and their children didn't have sex with one another to make more humans, humans would have died out with them. Yet there are literally billions of humans on the planet.
So if the Eve and Adam story is true, humanity came from incest.
Personally, I don't believe the Eve and Adam story is true but I'm not a christian.
If you claim to be a christian, you believe that story and the fact that humans came from incest.
And by the way, if Eve and Adam were the first and only 2 humans on the planet, who developed a language and who taught it to the snake?