Is it reasonable to believe that the whole human race is descended from Adam and Eve? Their story is generally dismissed as mere myth and there are even sincere Christians who would claim that God created a ‘race’; of humans rather than just two individual persons. Let us therefore have a look in a bit more detail.
Every human being has two full sets of genes, one inherited from each parent. Adam and Eve would therefore have had four full sets of genes between them (albeit not inherited if they were created by God). The complexity of human genes and the way that they interact is such that it is scientifically feasible for four full sets of genes to be able to provide the massive variety of characteristics seen across the human race.
The Genesis account names three sons of Adam and Eve, namely Cain, Abel and Seth, and it is recorded that Cain and Seth both produced offspring. But where did they get their wives from if God did not create any other human beings? It is inevitable that Adam and Eve will have produced a large number of children and so Cain and Seth will quite simply have married their sisters! This may come as a surprise as the law of Moses strictly forbade sexual relations between close relatives and such laws still exist in our modern society. Close inter-breeding is considered to be unsafe because of the increased risk of producing defective offspring. So why was it OK at the time of Adam and Eve?
Genetically the human race was created to absolute perfection, and so at first there would have been absolutely no risk involved in inter-breeding between close relatives. As imperfection was introduced things would have changed. The changes resulting from the Flood would have caused the levels of radiation in the environment to have increased, and this would produce an increased risk of genetic mutations. As described in the section on genetics, mutations will normally be ineffectual at the very best and more often detrimental.