What does Genesis 5:1 mean?

Chapter 5 is the beginning of a new section in the book of Genesis. It begins with a brief restating of God's creation of humanity and then provides a specific genealogy of the descendants of Adam through Seth and the succeeding generations to Noah.

Verse 1 describes this section as a book. In the era of the original writing, this most likely meant a clay tablet. This passage describes itself as "the book of the generations of Adam." The Hebrew word here is ā'dām, used both for the proper name of the first man, as well as the generic term for those who came after him. The same word used for man or mankind is also translated as Adam when referring to this first man. This, then, is a book of the generations of "man."

This verse restates the claim of Genesis 1:27 that God created Adam, mankind, in His own likeness. This does not mean that God has some physical form, or that Adam physically resembled God. John 4:24 tells us that God is a spirit. It does mean, however, that God created mankind to stand "in His image." As His representatives on earth, we rule and subdue His creation. It also carries the idea that humankind is essentially different from all the animals God made. We share with Him the experience of truth, beauty, meaning, will, and reason. Finally, the truth that all humans are made in the likeness of God means that all humans have enormous value and are worthy of great respect (James 3:9).