This is flesh of my flesh and bone of my bones...

Sin was commited after Eve's "eye" opened in the tree of knowledge. The walking God admits they indeed became like "them" (gods using majestic plural) by taking the fruit of good and evil. He said "now they will indeed take the (other) fruit of everlasting life" and hence he drove them away and stopped the entrance.

But then again, the tree was related to sex, to discover the nudity in specific parts of the body , to pregancy and the reptile "who did that".....