The text of Genesis 4-5
Genesis 4 and Genesis 5 come form distinct sources.
Under the traditional Documentary Hypothesis' categorization, Genesis 4, along with 5.28b-291 come from the J (Yahwist) source, while the rest of Genesis 5 (minus 28b-29) come from P (Priestly) source.2 They each grew out of a common source, but with a few small editions made to unify the two texts together, they were placed in sequence (i.e. as the complete text we call Genesis 4-5).
Alternately, another hypothesis is that the J form of the genealogy (4,5.28b-29) existed first, and the P form (5.1-28a,30-32) is a revision of J.
In any case, the point is that Genesis 4-5 actually provides us with two versions of the same lineage.
- Cain (קין) = Cainan (קינן)
- Enoch (חנוך) = Enoch (חנוך)
- Irad (עירד) = Yared (ירד)
- Mehuyael (מחיאל) = Mahalalel (מהללאל)
- Methushael (מתושאל) = Methushelah (מתושלח)
- Lamech (למך) = Lamech (למך)
Some names are spelled slightly different, and some have been rearranged relative to the other order. When the two sources are separated, they both conclude with Lamech fathering a son named Noah.3 The emended J source would read something like the following (though the exact placement of the restored 5.28b-29 is uncertain):
Cain knew his wife, and she conceived and bore Enoch; and he built a city, and named it Enoch after his son Enoch. To Enoch was born Irad; and Irad was the father of Mehujael, and Mehujael the father of Methushael, and Methushael the father of Lamech.
Lamech took two wives; the name of one was Adah, and the name of the other Zillah. Adah bore Jabal; he was the ancestor of those who live in tents and have livestock. His brother’s name was Jubal; he was the ancestor of all those who play the lyre and pipe. Zillah bore Tubal-cain, who made all kinds of bronze and iron tools. The sister of Tubal-cain was Naamah.
Lamech said to his wives: ‘Adah and Zillah, hear my voice; you wives of Lamech, listen to what I say: I have killed a man for wounding me, a young man for striking me. If Cain is avenged sevenfold, truly Lamech seventy-sevenfold.’
Adam knew his wife again, and she bore a son and named him Seth, for she said, ‘God has appointed for me another child instead of Abel, because Cain killed him.’ To Seth also a son was born, and he named him Enosh. At that time people began to invoke the name of Yahweh.
[To Lamech was born] a son; he named him Noah, saying, ‘Out of the ground that Yahweh has cursed this one shall bring us relief from our work and from the toil of our hands.’
Because Genesis 4,5.28b-29 and Genesis 5.1-28a,30-32 are alternate forms of the same lineage (whether independently evolving from a common source, or the latter reworking the former), this means that within the original J source it was not portraying Cain's lineage as inventive in contrast to an uninventive lineage from Seth.
Within the J narrative, Cain's lineage is the only lineage by the time of Lamech's sons, and the invention of cities, nomadic herding, musical instruments, and metalcrafting is simply the result of the human population growing beyond the initial primitivity of Adam and Eve living in paradise.
Going beyond the source criticism of the Documentary Hypothesis and related theories, there are an array of more speculative ideas. In one, Cain is the eponymous ancestor of the Kenite tribe, and the sons of Lamech correspond to the culture of the tribe; e.g., 'Tubal' is a word taken as 'metal-worker', associated with the metal-working Tubal people mentioned in Ezekiel 27.13, so that 'Tubal-cain' literally just means 'metal-working Kenite'.4 In another, the story is a distorted recollection of Greek myths that traveled to the Near East: 'Jubal Lamechson corresponds to Orpheus, and Tubal-Cain Lamechson to the smiths Hephaestus or Vulcan'.5 In these ideas, there is little moral judgment to be passed on Cain's lineage; it is only a mythic recollection of one tribe or another's ancestry.
Within Second Temple Judaism, the story of Genesis 4 and 6 undergoes reinterpretation. While the narrative of Genesis gives no such indication, books like 1 Enoch make the claim that Cain's lineage -- or rather, humanity in general -- was taught metalcrafting by angels (the 'sons of God' in Genesis 6.2).
1 Enoch 6.1-2
And it came to pass when the sons of men had multipled in those days, beautiful and comely daughters were born to them. And the watchers, the sons of heaven, saw them and desired them. And they said to one another, "Come, let us choose wives for ourselves from the daughters of men, and let us beget children for ourselves."
1 Enoch 7.1, 8.1
These [leaders of the watchers] and all the others [of two hundred watchers] with them took wives for themselves from among all whom they chose. And they began to go in to them, and to defile themselves with them, and to teach them sorcery and spellbinding, and to reveal to them the cutting of roots and herbs. [...] Azazel taught men to make swords of iron and weapons and shields and breastplates and every instrument of war. And he showed them the metals of the earth, and how they should work gold, to fashion it suitably; and concerning silver, to fashion it for bracelets and ornaments for women.
In 1 Enoch, this learning of metalcrafting is presented as a bad thing, though that may only be because such metalcrafting was used for violence and vanity, and was taught alongside various forms of magic, directly leading to the corruption of the earth that necessitates the flood in Genesis 6. (The Book of Jubilees, which reinterprets both Genesis and 1 Enoch together, presents the watchers as initially teaching humanity 'judgment' and 'uprightness', and only later choosing to marry human women 'so as to be defiled'. Jubilees makes no comment on the origin of the specific skills of Jabal, Jubal, and Tubal-cain as far as I can find.)
1 HarperCollins Study Bible - Student Edition, page 13: '5.28-29 In a brief insert from the J source, Lamech derives the name Noah from the word relief'. Names where their symbolic value is spelled out for the reader are prevalent throughout Genesis 2-4, commonly accepted as the beginning of the J source narrative.
2 Johnstone, Moberly, Rogerson, Genesis and Exodus, page 84: 'In Genesis 5.1-28, 30-32 we have what is ascribed by source criticism to the P source; and it is interesting that the list of ancestors has similarities with what is regarded as the J passage of 4.17-21.'
3 Hendel, Reading Genesis: Ten Methods, page 58, footnote 31: 'I attribute the report of Noah's birth (5:29) to J, where it was originally located at the end of the Cainite genealogy (Genesis 4:25-26); see also Friedman's similar treatment of 5:29 in Hidden, 74. In other words, J's Noah is a descendant of Cain, not Seth.' Johnstone, et al., Genesis and Exodus, page 85: 'Genesis 5.29 is assigned by source criticism to J because of its reference back to the cursing of the ground and the toil of labour (3.17; 4.12).'
4 E.g. Graves, Patai, Hebrew Myths: The Book of Genesis, page 110.
5 Brichto, The Names of God: Poetic Readings in Biblical Beginnings, page 168.