Question: "What is the definition of antediluvian?"
Answer: Antediluvian (literally, “before the flood”) refers to the time period before the flood recorded in Genesis 6—8. The righteous people who lived before Noah’s time are called antediluvian patriarchs. Those men are listed in Genesis 5 and include Adam, Seth, Enosh, Kenan, Enoch, and Methuselah, who lived to be 969, making him the oldest person on record. The word antediluvian has also come to mean “extremely old” or “out-of-date.”
We know from the genealogies listed in Genesis 1—6 that people lived much longer in antediluvian times than they do today. Adam, the first man, lived to be 930 years old (Genesis 5:5). His son Seth lived to be 912 (Genesis 5:8). The length of the antediluvian period, based on the genealogies, was approximately 1,656 years.
A significant change in human behavior occurred in the antediluvian period: “Men began to call on the name of the LORD” (Genesis 4:26). This fact is linked with the birth of Seth and then his son Enosh, indicating that, with the birth of Enosh, the family of Seth began to separate themselves from the wickedness of the world around them and were known as people who worshiped the Lord. The general trend of humanity, however, was spiritual decline. By the beginning of chapter 6, “The LORD saw how great the wickedness of the human race had become on the earth, and that every inclination of the thoughts of the human heart was only evil all the time” (verse 5).
The antediluvian era was also the time of the Nephilim. These were “heroes of old, men of renown,” who were the offspring of an unholy union between the “sons of God and the daughters of men” (Genesis 6:4). Whatever the exact nature of the Nephilim, they were one of the reasons God destroyed everything with a flood. Noah and his wife were not of the Nephilim race and therefore could repopulate the earth as God intended it to be.
Jesus alluded to the antediluvian period when He predicted signs of His second coming: “As it was in the days of Noah, so it will be at the coming of the Son of Man. For in the days before the flood, people were eating and drinking, marrying and giving in marriage, up to the day Noah entered the ark; and they knew nothing about what would happen until the flood came and took them all away. That is how it will be at the coming of the Son of Man” (Matthew 24:37–39).
The antediluvian period was unique in human history—a time of long life spans and bodies that were near perfection. Adam lived through more than half of the antediluvian days and was presumably available to recount firsthand accounts of Eden to anyone interested enough to listen. But it didn’t take long for wickedness to grow to such an extent that God had to destroy it all. After the flood, God promised Noah that He would never again flood the entire earth. The symbol of that promise was a rainbow (Genesis 9:12–17). That first rainbow signified the end of the antediluvian era and demonstrated God’s great mercy in giving humanity another chance to know Him. Every rainbow since then is a continuing reminder of the grace of God.