1 This is the book of the genealogy of Adam. In the day that God created man, He made him in the likeness of God.
2 He created them male and female, and blessed them and called them Mankind in the day they were created.
3 And Adam lived one hundred and thirty years, and begot a son in his own likeness, after his image, and named him Seth.
4 After he begot Seth, the days of Adam were eight hundred years; and he had sons and daughters.
5 So all the days that Adam lived were nine hundred and thirty years; and he died.
The main point of this section [Genesis 5:1-11:9] is that human depravity is here to stay—that it is, in fact, endemic to the human condition. This is driven home by the two grand narrative episodes contained in this section—the Flood and the building of Babel/Babylon. Both episodes make clear that depravity (i.e., the predilection to sin) is not the result of an environment or circumstance (though this may certainly exacerbate the expression of depravity)—that is, in the terminology of the modern debate, nurture—but rather it is the result of our nature, and hence to be found in every individual. It is essential, therefore, to the point of this last section that the scope of these two grand events be understood exactly as the text presents them—to wit, as events which, in both instances, encompass all (not most or the Middle-Eastern) portion of humanity. — Wechsler, page 127.
In the first verse of Genesis 5, the writer recalls again that God created man “in the likeness of God.” But then, in verse 3, he says that Adam “begat a son in his own likeness, after his image, and called his name Seth.” Between Adam and Seth intervened the Fall. Though Adam was created in God’s image, Seth was begotten in Adam’s image; he therefore partook of the fallen nature of his father (note Romans 5:12-14). — Morris, pages 150-151.
These verses [vs. 1-2] obviously refer to Genesis 1:26-28. The reason for this is clearly to tie this new section back to the first record. The first was the toledoth of “the heavens and the earth” (Genesis 2:4), the “book of the toledoth of Adam” (5:1) has just been completed and now, much later, “the toledoth of Noah” (6:9) is beginning to be inscribed. It was necessary for Noah’s record to be identified with both of the others, as a continuation of the “official” history of the human race and specially of the line of promise. Furthermore, this brief summary then makes this section a complete record of the antediluvian patriarchs, from the date of Creation down to the birth of Shem, Ham, and Japheth. It therefore provides the chronological framework of history from Creation to the Flood. — Morris, page 152.
Genesis 5:5 gives Adam’s obituary announcement, fulfilling the physical aspect of the death sentence pronounced on him in Genesis 3:19 and assuring all of humanity that “the wages of sin is death” (Romans 6:23). — Morris, page 153.
A straightforward reading of the biblical genealogies from the reliable Masoretic text shows that Adam was created about 4000 B.C. and that the Flood occurred around 2500 B.C. Contextual, linguistic, and historical analyses of the book of Genesis confirm that the chronogenealogies are a complete record with no gaps. Creationists who wish to push back the date of the Flood and creation to fit their geological or archaeological theories have no ground to do this based on the biblical record. — Taylor, page 129.
These opening verses reiterate the central idea set forth in 1:26-28, to wit: that mankind (both males and females equally) was created—uniquely among all living creatures—in the likeness of God. By repeating this point here, after mankind’s Fall from perfection, we are being reminded that this fundamental divine “likeness” remains intact—and so to, by implication, do we retain our pride of place as the crowning recipient of God’s blessing, both materially, as the administrators and prime benefactors of Creation, and spiritually, as those who have been uniquely privileged with the potential of experiencing spiritual “wholeness”—that is, unbroken and complete relationship with our Creator-Father. To this is also here added—and for the first time stated explicitly—that God named humanity in the day when He created them, the point of which, in the present context, is two-fold: one the one hand, as indicated by the act of naming in general, to underscored God’s continuing dominion over mankind (now despite the advent of depravity); and, on the other hand, to underscore God’s continuing paternal role as the Father of mankind, as underscored by the observation that both throughout this chapter, as in the Bible generally, the name of a son is given by his father. — Wechsler, page 128.