Daniel 2:43 refers to ten nations united by "iron" mixed with "clay."
Daniel 2:43 (NASB)
43 And in that you saw the iron mixed with common clay, they will combine with one another in the seed of men; but they will not adhere to one another, even as iron does not combine with pottery.
The "seed of man" is human Government, if we accept the usage from the prophet Jeremiah, who uses the same words in the context of the New Covenant (Jer 31:27-30).
In the general context of the Book or Daniel and the Book of Revelation, iron appears to be autocracy, and the clay pluralism. That is, the autocracy that unites the ten nations of the union is at the same time "weakened" by the pluralism or democratic form of Government of each individual state. In other words, this European Union is both a federation (one common union) and confederation (separate nation states).
For example, in the Revelation narrative, the respective heads of state of these ten nations are the "heads" which govern. That is, the confederation (separate nation states) carry the "diadem" of authority within the framework of the federation of the European Union.
Revelation 12:3 (NASB)
3Then another sign appeared in heaven: and behold, a great red dragon having seven heads and ten horns, and on his heads were seven diadems.
The diadems represent the control, or rulership. That is, the confederation (separate nation states) maintain the locus of control, since they possess the diadems. Seven of the nations are ruling as democratic forms of Government until the "horns" take over.
Revelation 13:1 (NASB)
3 And the dragon stood on the sand of the seashore. Then I saw a beast coming up out of the sea, having ten horns and seven heads, and on his horns were ten diadems, and on his heads were blasphemous names.
The "horns" now carry the power (and not the "heads"), which now represents complete autocracy over the ten nations under the beast. (In the Revelation, "beast" refers either to the person, who is an individual, and/or to the ten nations, which is "beast" collective.) In other words, the individual beast and collective beast "surfaced" (appeared) when the individual extirpated the three principal "heads" of the collective as described in the Book of Daniel.
Daniel 7:7-8 (NASB)
7 After this I kept looking in the night visions, and behold, a fourth beast, dreadful and terrifying and extremely strong; and it had large iron teeth. It devoured and crushed and trampled down the remainder with its feet; and it was different from all the beasts that were before it, and it had ten horns. 8 While I was contemplating the horns, behold, another horn, a little one, came up among them, and three of the first horns were pulled out by the roots before it; and behold, this horn possessed eyes like the eyes of a man and a mouth uttering great boasts.
So the "little horn" was one of the heads, who has extirpated three heads. Thus the following verse in the Revelation makes plain sense.
Revelation 17:9-13 (NASB)
9 Here is the mind which has wisdom. The seven heads are seven mountains on which the woman sits, 10 and they are seven kings; five have fallen, one is, the other has not yet come; and when he comes, he must remain a little while. 11 The beast which was and is not, is himself also an eighth and is one of the seven, and he goes to destruction. 12 The ten horns which you saw are ten kings who have not yet received a kingdom, but they receive authority as kings with the beast for one hour. 13 These have one purpose, and they give their power and authority to the beast.
The individual, who is one of the heads of state, extirpates three of the heads of state (and their pluralistic forms of government). Of the remaining seven heads of state (and their pluralistic forms of government), five of them "cave in" to autocracy with no resistance. The other two remain, one of which is the individual--the beast.
In summary, the "heads" are the leaders and cabinets of the democratically-elected forms of government (or mountains), which are "clay." The "heads" of the three major nations of this ten nation union are subsequently extirpated according to Daniel 7:7-8. The individual beast then usurps the ten governments by transferring the diadems from the "heads" (democracy) to the "horns" (autocracy). In other words, the three heads are usurped by the little horn if and when the Book of Daniel is "read into" the Revelation.
Whether or not one agrees (or disagrees) with this explanation, suffice to say: Genesis 6:1-4 has no relevance with Daniel 2:43. The closest relevance would be 1 Pet 3:18-20, where the Spirit of Jesus (through the testimony of Noah) had testified against the antediluvian generation, which are now incarcerated in the underworld. That is, there was eating and drinking; marrying and giving in marriage, but no repentance before the imminent day of judgment.