It's worth noting that there were survivors of the flood according to Josephus, which may have included some in the genealogy of Adam:
"Now all the writers of barbarian histories make mention of this flood, and of this ark; among whom is Berossus the Chaldean. For when he was describing the circumstances of the flood, he goes on thus: "It is said, there is still some part of this ship in Armenia, at the mountain of the Cordyaeans; and that some people carry off pieces of the bitumen, which they take away, and use chiefly as amulets, for the averting of mischiefs."--Hieronymus the Egyptian also, who wrote the Phenician antiquities, and Manases, and a great many more, make mention of the same. Nay, Nicholas of Damascus, in his ninety-sixth book, hath a particular relation about them; where he speaks thus: "There is a great mountain in Armenia, over Minyas, called Baris, upon which it is reported, that many who fled at the time of the deluge were saved; and that one who was carried in an ark, came on shore upon the top of it; and that the remains of the timber were a great while preserved. This might be the man about whom Moses the legislator of the Jews wrote."
"Now the sons of Noah were three - Shem, Japhet, and Ham, born one hundred years before the Deluge. These first of all descended from the mountains into the plains, and fixed their habitation there; and persuaded others who were greatly afraid of the lower grounds on account of the flood, and so were very loath to come down from the higher places, to venture to follow their examples."
