25. If one clings to the literal meaning of Genesis, behold to what consequences one arrives. From it we learn that Adam and Eve were alone in the world after their expulsion from the terrestrial paradise. It is subsequent to that that Cain and Abel were born. Now, Cain having killed his brother, and having been exiled of another country, saw his father and mother no more; and they were again alone. It is only a long time after, at the age of a hundred and thirty years, that Adam had a third son called Seth. After the birth of Seth, he still lived, according to biblical genealogy, eight hundred years, and begat sons and daughters.
When Cain established himself eastward of Eden, according to Genesis, there were only three persons upon the Earth — Adam, Eve, and Cain. However, he had a wife and child. Who could this woman have been? And where could he have found her? The Hebrew text says: He was building a city, and not he built, which indicates a present action and not an anterior one; but many inhabitants are necessary to make a city: for it is not possible or presumable that he made it for himself, wife, and son, or that he was able to construct it by himself alone.
It is necessary to infer, from this recital, that the country was peopled. Now this could not have been by the descendants of Adam, who then had no other children than Cain.
The presence of other inhabitants is also proved by this saying of Cain: “I will be a restless wanderer on the Earth, and whoever finds me will kill me,” and from the reply God made to it. By whom could he have been killed? And for what good could the sign which god placed on his forehead have been needed if he was not to encounter anyone? If, then, there were upon Earth other men outside of the family of Adam, they must have been there before him, whence this sequence, drawn from even the text of Genesis, that Adam is neither the first not the only father of human beings (chap. XI, n° 34). *
* This idea is not new. La Peyrère, the wise theologian of the seventh century in his book “Préadamites,” written in Latin and published in 1655, extracted from the original biblical text, this being subsequently adulterated by the translations, the clear evidence that the Earth was inhabited before Adam; today this is the opinion of many enlightened ecclesiastics.