Genesis 11:10

These are the generations of Shem: Shem was an hundred years old, and begat Arphaxad two years after the flood:

Genesis 11:10 opens the genealogy from Shem to Abraham that shows how long the patriarchs overlapped and how directly the instruction God gave to Adam was handed down. Shem was one hundred years old when Arphaxad was born two years after the Flood, and he then lived five hundred more years, while Noah lived three hundred and fifty years after the Flood. The overlaps were close: Methuselah lived until Shem was ninety-eight years old, Shem lived until one hundred and fifty years after Abraham was born and fifty years after Isaac was born, Abraham lived until Jacob and Esau were fifteen years old, and Isaac lived until they were one hundred and twenty.

What God taught Adam was thus passed directly from Adam to Methuselah, from Methuselah to Shem, from Shem to Abraham and Isaac, and from Abraham and Isaac to Jacob, the father of the tribes of Israel. God intended that as people went out to found nations in different parts of the earth they would carry a knowledge of His will so that the light of truth would shine undimmed to succeeding generations. The long lives of Noah, the faithful preacher of righteousness, and Shem gave their descendants opportunity to become acquainted with God's requirements and the history of His dealings with their fathers.

Those who set themselves against God lost this opportunity because they were unwilling to listen to these unwelcome truths and had no desire to retain God in their knowledge. By the confusion of tongues they were in great measure shut out from intercourse with those who might have given them light. The verse belongs to the generations after the Flood when human life spans began to decline, for the patriarchs from Adam to Noah, with few exceptions, lived nearly a thousand years. Nine generations before the Flood averaged nine hundred and twelve years of age, while nine generations after the Flood averaged three hundred and thirty-two years.

That decline proves mankind has woefully deteriorated physically, continuing downward to seventy years in the time of Moses and to about thirty-five years at the present.