Above is a section of the tablet Irving discusses.
A claim made in the Sumerian King List says: In ancient Mesopotamia, the Sumerian King List reads
After kingship came down from heaven .... the kingship was taken to Shuruppak. In Shuruppak, Ubara-Tutu became king; he ruled for 5 sars and 1 ner. In 5 cities 8 kings; they ruled for 241,200 years. Then the flood swept over.
So you can note the claim of the extraordinary long lives led by pre-flood worthies.
If you're interested in all the the legends of destructive floods, Wikipedia may be a good general view of these stories.
It says: "The Mesopotamian flood stories concern the epics of Ziusudra, Gilgamesh, and Atrahasis. The Sumerian King List relies on the flood motif to divide its history into preflood (antediluvian) and postflood periods. The preflood kings had enormous lifespans, whereas postflood lifespans were much reduced. The Sumerian flood myth found in the Deluge tablet was the epic of Ziusudra, who heard the gods' plan to destroy humanity, in response to which he constructed a vessel that delivered him from great waters.[2] In the Atrahasis version, the flood is a river flood.[3]
In the Genesis mythology of the Hebrew Bible, Yahweh decides to flood the earth because of the depth of the sinful state of mankind. Righteous Noah is given instructions to build an ark. When the ark is completed, Noah, his family, and representatives of all the animals of the earth are called upon to enter the ark. When the destructive flood begins, all life outside of the ark perishes. After the waters recede, all those aboard the ark disembark and have Yahweh's promise that he will never judge the earth with a flood again. He causes a rainbow to form as the sign of this promise.[4]
In the 19th century, Assyriologist George Smith translated the Babylonian account of a great flood. Further discoveries produced several versions of the Mesopotamian flood myth, with the account closest to that in Genesis found in a 700 BC Babylonian copy of the Epic of Gilgamesh.[5]:20 In this work, the hero Gilgameshmeets the immortal man Utnapishtim, and the latter describes how the god Ea instructed him to build a huge vessel in anticipation of a deity-created flood that would destroy the world. The vessel would save Utnapishtim, his family, his friends, and the animals.[6]
In Hindu mythology, texts such as the Satapatha Brahmana and the Puranas contain the story of a great flood,[7] wherein the Matsya Avatar of Vishnu warns the first man, Manu, of the impending flood, and also advises him to build a giant boat.[8][9][10]
In Plato's Timaeus, Timaeus says that because the Bronze race of Humans had been making wars constantly Zeus was angered and decided to punish humanity by a flood. Prometheus the Titan knew of this and told the secret to Deucalion, advising him to build an ark in order to be saved. After nine nights and days, the water started receding and the ark was landed at Mount Parnassus.[11]"
In the example of Plato's story we may be noting that his version of what he had heard (or, read) was adapted to suit Greek religion and history.
Is that what the author of the Genesis document also did?