The first men were indeed so created, that if they had not sinned, they would not have experienced any kind of death; but that, having become sinners, they were so punished with death, that whatsoever sprang from their stock should also be punished with the same death. For nothing else could be born of them than that which they themselves had been. Their nature was deteriorated in proportion to the greatness of the condemnation of their sin, so that what existed as punishment in those who first sinned, became a natural consequence in their children.
…
In the first man, therefore, there existed the whole human nature, which was to be transmitted by the woman to posterity, when that conjugal union received the divine sentence of its own condemnation; and what man was made, not when created, but when he sinned and was punished, this he propagated, so far as the origin of sin and death are concerned.
— City of God XIII.3
