Genesis 5:9 MEANING

Genesis 5:9
(9) Enos lived ninety years.--This proves that the years could not have been mere revolutions of the moon, as some have supposed. So Cainan was only seventy years of age at the birth of his son, and Mahalaleel sixty-five. In the LXX. no patriarch has a son until he is at least 162 years of age, so that the supposition there would be more tenable.

5:6-20 Concerning each of these, except Enoch, it is said, and he died. It is well to observe the deaths of others. They all lived very long; not one of them died till he had seen almost eight hundred years, and some of them lived much longer; a great while for an immortal soul to be prisoned in a house of clay. The present life surely was not to them such a burden as it commonly is now, else they would have been weary of it. Nor was the future life so clearly revealed then, as it now under the gospel, else they would have been urgent to remove to it. All the patriarchs that lived before the flood, except Noah, were born before Adam died. From him they might receive a full account of the creation, the fall, the promise, and the Divine precepts about religious worship and a religious life. Thus God kept up in his church the knowledge of his will.And Enos lived ninety years, and begat Cainan. According to the Septuagint a hundred and ninety years; it can hardly be thought but that he had sons or daughters before, but this is only taken notice of for a reason before given.
Courtesy of Open Bible