Did Adam and Eve commit incest?
The Genesis account of Creation provides mankind with just the bare facts we need to know about our origin; we wish we knew more! Nevertheless, the account concludes with, "Then God saw everything that He had made and indeed it was very good" (Genesis 1:31). From this we infer that every detail was perfect including the bodies of Adam and Eve. This would mean there were no genetic defects and no mutations when the very first commandment was given "to be fruitful and multiply" (Genesis 1:28).
In the absence of genetic defects, Adam and Eve's offspring would also have been perfect, and Scripture says nothing to forbid incest. Nevertheless, the disobedience at the tree of good and evil took place before there were any children. The account then continues where God confronted Adam and then cursed, not Adam but "the ground for his sake" (Genesis 3:17). From that moment, everything that Adam – and mankind since – had eaten has grown in the cursed ground. Cell by living cell, Adam began to change from his initial state of perfection to mortal imperfection, and mankind has increasingly acquired those genetic defects. Although today we all carry those mutated genes, when two people marry who by chance have the same defective gene, that gene will be expressed in their offspring. The chances are increased enormously when the married couple are closely related, especially when brother and sister. For this reason such unions are said to be incestuous and have long been declared illegal.
The build-up of defective genes in the human gene pool was slow at first, taking many generations, and it may only have become evident at about the time of Moses in Egypt. For example, the Pharaoh married his sister as his first wife to ensure the kingdom stayed in the family. Pharaoh Akhnaton (reigned from 1379-1362 BC) had been the product of such a union and from his preserved image he is acknowledged to have been genetically deformed. Charles Darwin married his first cousin and had ten children, three of whom suffered very early deaths, suggesting genetic problems. Illegal marriages in England have long since been extended to first cousins.